io package - io - Go Packages

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class="go-Main-navDesktop"> <div class="UnitOutline-jumpTo"> <button class="UnitOutline-jumpToInput go-ShortcutKey js-jumpToInput" aria-controls="jump-to-modal" aria-label="Open Jump to Identifier" data-shortcut="f" data-shortcut-alt="find" data-test-id="jump-to-button" data-gtmc="outline button"> Jump to ... </button> </div> <ul class="go-Tree js-tree" role="tree" aria-label="Outline"> <li> <a href="#section-documentation" data-gtmc="outline link"> Documentation </a> <ul> <li> <a href="#pkg-overview" data-gtmc="doc outline link">Overview</a> </li> <li class="DocNav-overview"> <a href="#pkg-index" data-gtmc="doc outline link"> Index </a> <ul> <li> <a href="#pkg-examples" data-gtmc="doc outline link"> Examples </a> </li> </ul> </li> <li class="DocNav-constants"> <a href="#pkg-constants" data-gtmc="doc outline link"> Constants </a> </li> <li class="DocNav-variables"> <a href="#pkg-variables" data-gtmc="doc outline link"> Variables </a> </li> <li class="DocNav-functions"> <a href="#pkg-functions" data-gtmc="doc outline link"> Functions </a> <ul> <li> <a href="#Copy" title="Copy(dst, src)" data-gtmc="doc outline link"> Copy(dst, src) </a> </li> <li> <a href="#CopyBuffer" title="CopyBuffer(dst, src, buf)" data-gtmc="doc outline link"> CopyBuffer(dst, src, buf) </a> </li> <li> <a href="#CopyN" title="CopyN(dst, src, n)" data-gtmc="doc outline link"> CopyN(dst, src, n) </a> </li> <li> <a href="#Pipe" title="Pipe()" data-gtmc="doc outline link"> Pipe() </a> </li> <li> <a href="#ReadAll" title="ReadAll(r)" data-gtmc="doc outline link"> ReadAll(r) </a> </li> <li> <a href="#ReadAtLeast" title="ReadAtLeast(r, buf, min)" data-gtmc="doc outline link"> ReadAtLeast(r, buf, min) </a> </li> <li> <a href="#ReadFull" title="ReadFull(r, buf)" data-gtmc="doc outline link"> ReadFull(r, buf) </a> </li> <li> <a href="#WriteString" title="WriteString(w, s)" data-gtmc="doc outline link"> WriteString(w, s) </a> </li> </ul> </li> <li class="DocNav-types"> <a href="#pkg-types" data-gtmc="doc outline link"> Types </a> <ul> <li> <a href="#ByteReader" title="type ByteReader" data-gtmc="doc outline link"> type ByteReader </a> </li> <li> <a href="#ByteScanner" title="type ByteScanner" data-gtmc="doc outline link"> type ByteScanner </a> </li> <li> <a href="#ByteWriter" title="type ByteWriter" data-gtmc="doc outline link"> type ByteWriter </a> </li> <li> <a href="#Closer" title="type Closer" data-gtmc="doc outline link"> type Closer </a> </li> <li> <a href="#LimitedReader" title="type LimitedReader" data-gtmc="doc outline link"> type LimitedReader </a> <ul> <li> <a href="#LimitedReader.Read" title="(l) Read(p)" data-gtmc="doc outline link"> (l) Read(p) </a> </li> </ul> </li> <li> <a href="#OffsetWriter" title="type OffsetWriter" data-gtmc="doc outline link"> type OffsetWriter </a> <ul> <li> <a href="#NewOffsetWriter" title="NewOffsetWriter(w, off)" data-gtmc="doc outline link"> NewOffsetWriter(w, off) </a> </li> <li> <a href="#OffsetWriter.Seek" title="(o) Seek(offset, whence)" data-gtmc="doc outline link"> (o) Seek(offset, whence) </a> </li> <li> <a href="#OffsetWriter.Write" title="(o) Write(p)" data-gtmc="doc outline link"> (o) Write(p) </a> </li> <li> <a href="#OffsetWriter.WriteAt" title="(o) WriteAt(p, off)" data-gtmc="doc outline link"> (o) WriteAt(p, off) </a> </li> </ul> </li> <li> <a href="#PipeReader" title="type PipeReader" data-gtmc="doc outline link"> type PipeReader </a> <ul> <li> <a href="#PipeReader.Close" title="(r) Close()" data-gtmc="doc outline link"> (r) Close() </a> </li> <li> <a href="#PipeReader.CloseWithError" title="(r) CloseWithError(err)" data-gtmc="doc outline link"> (r) CloseWithError(err) </a> </li> <li> <a href="#PipeReader.Read" title="(r) Read(data)" data-gtmc="doc outline link"> (r) Read(data) </a> </li> </ul> </li> <li> <a href="#PipeWriter" title="type PipeWriter" data-gtmc="doc outline link"> type PipeWriter </a> <ul> <li> <a href="#PipeWriter.Close" title="(w) Close()" data-gtmc="doc outline link"> (w) Close() </a> </li> <li> <a href="#PipeWriter.CloseWithError" title="(w) CloseWithError(err)" data-gtmc="doc outline link"> (w) CloseWithError(err) </a> </li> <li> <a href="#PipeWriter.Write" title="(w) Write(data)" data-gtmc="doc outline link"> (w) Write(data) </a> </li> </ul> </li> <li> <a href="#ReadCloser" title="type ReadCloser" data-gtmc="doc outline link"> type ReadCloser </a> <ul> <li> <a href="#NopCloser" title="NopCloser(r)" data-gtmc="doc outline link"> NopCloser(r) </a> </li> </ul> </li> <li> <a href="#ReadSeekCloser" title="type ReadSeekCloser" data-gtmc="doc outline link"> type ReadSeekCloser </a> </li> <li> <a href="#ReadSeeker" title="type ReadSeeker" data-gtmc="doc outline link"> type ReadSeeker </a> </li> <li> <a href="#ReadWriteCloser" title="type ReadWriteCloser" data-gtmc="doc outline link"> type ReadWriteCloser </a> </li> <li> <a href="#ReadWriteSeeker" title="type ReadWriteSeeker" data-gtmc="doc outline link"> type ReadWriteSeeker </a> </li> <li> <a href="#ReadWriter" title="type ReadWriter" data-gtmc="doc outline link"> type ReadWriter </a> </li> <li> <a href="#Reader" title="type Reader" data-gtmc="doc outline link"> type Reader </a> <ul> <li> <a href="#LimitReader" title="LimitReader(r, n)" data-gtmc="doc outline link"> LimitReader(r, n) </a> </li> <li> <a href="#MultiReader" title="MultiReader(readers)" data-gtmc="doc outline link"> MultiReader(readers) </a> </li> <li> <a href="#TeeReader" title="TeeReader(r, w)" data-gtmc="doc outline link"> TeeReader(r, w) </a> </li> </ul> </li> <li> <a href="#ReaderAt" title="type ReaderAt" data-gtmc="doc outline link"> type ReaderAt </a> </li> <li> <a href="#ReaderFrom" title="type ReaderFrom" data-gtmc="doc outline link"> type ReaderFrom </a> </li> <li> <a href="#RuneReader" title="type RuneReader" data-gtmc="doc outline link"> type RuneReader </a> </li> <li> <a href="#RuneScanner" title="type RuneScanner" data-gtmc="doc outline link"> type RuneScanner </a> </li> <li> <a href="#SectionReader" title="type SectionReader" data-gtmc="doc outline link"> type SectionReader </a> <ul> <li> <a href="#NewSectionReader" title="NewSectionReader(r, off, n)" data-gtmc="doc outline link"> NewSectionReader(r, off, n) </a> </li> <li> <a href="#SectionReader.Outer" title="(s) Outer()" data-gtmc="doc outline link"> (s) Outer() </a> </li> <li> <a href="#SectionReader.Read" title="(s) Read(p)" data-gtmc="doc outline link"> (s) Read(p) </a> </li> <li> <a href="#SectionReader.ReadAt" title="(s) ReadAt(p, off)" data-gtmc="doc outline link"> (s) ReadAt(p, off) </a> </li> <li> <a href="#SectionReader.Seek" title="(s) Seek(offset, whence)" data-gtmc="doc outline link"> (s) Seek(offset, whence) </a> </li> <li> <a href="#SectionReader.Size" title="(s) Size()" data-gtmc="doc outline link"> (s) Size() </a> </li> </ul> </li> <li> <a href="#Seeker" title="type Seeker" data-gtmc="doc outline link"> type Seeker </a> </li> <li> <a href="#StringWriter" title="type StringWriter" data-gtmc="doc outline link"> type StringWriter </a> </li> <li> <a href="#WriteCloser" title="type WriteCloser" data-gtmc="doc outline link"> type WriteCloser </a> </li> <li> <a href="#WriteSeeker" title="type WriteSeeker" data-gtmc="doc outline link"> type WriteSeeker </a> </li> <li> <a href="#Writer" title="type Writer" data-gtmc="doc outline link"> type Writer </a> <ul> <li> <a href="#MultiWriter" title="MultiWriter(writers)" data-gtmc="doc outline link"> MultiWriter(writers) </a> </li> </ul> </li> <li> <a href="#WriterAt" title="type WriterAt" data-gtmc="doc outline link"> type WriterAt </a> </li> <li> <a href="#WriterTo" title="type WriterTo" data-gtmc="doc outline link"> type WriterTo </a> </li> </ul> </li> </ul> </li> <li> <a href="#section-sourcefiles" data-gtmc="outline link"> Source Files </a> </li> <li> <a href="#section-directories" data-gtmc="outline link"> Directories </a> </li> </ul> </div> <div class="go-Main-navMobile js-mainNavMobile"> <label class="go-Label"> <select class="go-Select"> <option selected disabled>Documentation</option> </select> </label> </div> </nav> <article class="go-Main-article js-mainContent"> <div class="UnitDetails" data-test-id="UnitDetails" style="display: block;"> <div class="UnitDetails-content js-unitDetailsContent" data-test-id="UnitDetails-content"> <div class="UnitDoc"> <h2 class="UnitDoc-title" id="section-documentation"> <img class="go-Icon" height="24" width="24" src="/static/shared/icon/code_gm_grey_24dp.svg" alt=""> Documentation <a class="UnitDoc-idLink" href="#section-documentation" title="Go to Documentation" aria-label="Go to Documentation">露</a> </h2> <div class="Documentation js-documentation"> <div class="Documentation-content js-docContent"> <section class="Documentation-overview"> <h3 tabindex="-1" id="pkg-overview" class="Documentation-overviewHeader">Overview <a href="#pkg-overview" title="Go to Overview" aria-label="Go to Overview">露</a></h3> <p>Package io provides basic interfaces to I/O primitives. Its primary job is to wrap existing implementations of such primitives, such as those in package os, into shared public interfaces that abstract the functionality, plus some other related primitives. </p><p>Because these interfaces and primitives wrap lower-level operations with various implementations, unless otherwise informed clients should not assume they are safe for parallel execution. </p> </section><section class="Documentation-index"> <h3 id="pkg-index" class="Documentation-indexHeader">Index <a href="#pkg-index" title="Go to Index" aria-label="Go to Index">露</a></h3> <ul class="Documentation-indexList"> <li class="Documentation-indexConstants"><a href="#pkg-constants">Constants</a></li> <li class="Documentation-indexVariables"><a href="#pkg-variables">Variables</a></li> <li class="Documentation-indexFunction"> <a href="#Copy">func Copy(dst Writer, src Reader) (written int64, err error)</a></li> <li class="Documentation-indexFunction"> <a href="#CopyBuffer">func CopyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error)</a></li> <li class="Documentation-indexFunction"> <a href="#CopyN">func CopyN(dst Writer, src Reader, n int64) (written int64, err error)</a></li> <li class="Documentation-indexFunction"> <a href="#Pipe">func Pipe() (*PipeReader, *PipeWriter)</a></li> <li class="Documentation-indexFunction"> <a href="#ReadAll">func ReadAll(r Reader) ([]byte, error)</a></li> <li class="Documentation-indexFunction"> <a href="#ReadAtLeast">func ReadAtLeast(r Reader, buf []byte, min int) (n int, err error)</a></li> <li class="Documentation-indexFunction"> <a href="#ReadFull">func ReadFull(r Reader, buf []byte) (n int, err error)</a></li> <li class="Documentation-indexFunction"> <a href="#WriteString">func WriteString(w Writer, s string) (n int, err error)</a></li> <li class="Documentation-indexType"> <a href="#ByteReader">type ByteReader</a></li> <li class="Documentation-indexType"> <a href="#ByteScanner">type ByteScanner</a></li> <li class="Documentation-indexType"> <a href="#ByteWriter">type ByteWriter</a></li> <li class="Documentation-indexType"> <a href="#Closer">type Closer</a></li> <li class="Documentation-indexType"> <a href="#LimitedReader">type LimitedReader</a></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#LimitedReader.Read">func (l *LimitedReader) Read(p []byte) (n int, err error)</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#OffsetWriter">type OffsetWriter</a></li> <li><ul class="Documentation-indexTypeFunctions"> <li> <a href="#NewOffsetWriter">func NewOffsetWriter(w WriterAt, off int64) *OffsetWriter</a></li> </ul></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#OffsetWriter.Seek">func (o *OffsetWriter) Seek(offset int64, whence int) (int64, error)</a></li> <li> <a href="#OffsetWriter.Write">func (o *OffsetWriter) Write(p []byte) (n int, err error)</a></li> <li> <a href="#OffsetWriter.WriteAt">func (o *OffsetWriter) WriteAt(p []byte, off int64) (n int, err error)</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#PipeReader">type PipeReader</a></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#PipeReader.Close">func (r *PipeReader) Close() error</a></li> <li> <a href="#PipeReader.CloseWithError">func (r *PipeReader) CloseWithError(err error) error</a></li> <li> <a href="#PipeReader.Read">func (r *PipeReader) Read(data []byte) (n int, err error)</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#PipeWriter">type PipeWriter</a></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#PipeWriter.Close">func (w *PipeWriter) Close() error</a></li> <li> <a href="#PipeWriter.CloseWithError">func (w *PipeWriter) CloseWithError(err error) error</a></li> <li> <a href="#PipeWriter.Write">func (w *PipeWriter) Write(data []byte) (n int, err error)</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#ReadCloser">type ReadCloser</a></li> <li><ul class="Documentation-indexTypeFunctions"> <li> <a href="#NopCloser">func NopCloser(r Reader) ReadCloser</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#ReadSeekCloser">type ReadSeekCloser</a></li> <li class="Documentation-indexType"> <a href="#ReadSeeker">type ReadSeeker</a></li> <li class="Documentation-indexType"> <a href="#ReadWriteCloser">type ReadWriteCloser</a></li> <li class="Documentation-indexType"> <a href="#ReadWriteSeeker">type ReadWriteSeeker</a></li> <li class="Documentation-indexType"> <a href="#ReadWriter">type ReadWriter</a></li> <li class="Documentation-indexType"> <a href="#Reader">type Reader</a></li> <li><ul class="Documentation-indexTypeFunctions"> <li> <a href="#LimitReader">func LimitReader(r Reader, n int64) Reader</a></li> <li> <a href="#MultiReader">func MultiReader(readers ...Reader) Reader</a></li> <li> <a href="#TeeReader">func TeeReader(r Reader, w Writer) Reader</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#ReaderAt">type ReaderAt</a></li> <li class="Documentation-indexType"> <a href="#ReaderFrom">type ReaderFrom</a></li> <li class="Documentation-indexType"> <a href="#RuneReader">type RuneReader</a></li> <li class="Documentation-indexType"> <a href="#RuneScanner">type RuneScanner</a></li> <li class="Documentation-indexType"> <a href="#SectionReader">type SectionReader</a></li> <li><ul class="Documentation-indexTypeFunctions"> <li> <a href="#NewSectionReader">func NewSectionReader(r ReaderAt, off int64, n int64) *SectionReader</a></li> </ul></li> <li><ul class="Documentation-indexTypeMethods"> <li> <a href="#SectionReader.Outer">func (s *SectionReader) Outer() (r ReaderAt, off int64, n int64)</a></li> <li> <a href="#SectionReader.Read">func (s *SectionReader) Read(p []byte) (n int, err error)</a></li> <li> <a href="#SectionReader.ReadAt">func (s *SectionReader) ReadAt(p []byte, off int64) (n int, err error)</a></li> <li> <a href="#SectionReader.Seek">func (s *SectionReader) Seek(offset int64, whence int) (int64, error)</a></li> <li> <a href="#SectionReader.Size">func (s *SectionReader) Size() int64</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#Seeker">type Seeker</a></li> <li class="Documentation-indexType"> <a href="#StringWriter">type StringWriter</a></li> <li class="Documentation-indexType"> <a href="#WriteCloser">type WriteCloser</a></li> <li class="Documentation-indexType"> <a href="#WriteSeeker">type WriteSeeker</a></li> <li class="Documentation-indexType"> <a href="#Writer">type Writer</a></li> <li><ul class="Documentation-indexTypeFunctions"> <li> <a href="#MultiWriter">func MultiWriter(writers ...Writer) Writer</a></li> </ul></li> <li class="Documentation-indexType"> <a href="#WriterAt">type WriterAt</a></li> <li class="Documentation-indexType"> <a href="#WriterTo">type WriterTo</a></li> </ul> </section><section class="Documentation-examples"> <h4 tabindex="-1" id="pkg-examples" class="Documentation-examplesHeader">Examples <a class="Documentation-idLink" href="#pkg-examples" title="Go to Examples" aria-label="Go to Examples">露</a></h4> <ul class="Documentation-examplesList"> <li><a href="#example-Copy" class="js-exampleHref">Copy</a></li> <li><a href="#example-CopyBuffer" class="js-exampleHref">CopyBuffer</a></li> <li><a href="#example-CopyN" class="js-exampleHref">CopyN</a></li> <li><a href="#example-LimitReader" class="js-exampleHref">LimitReader</a></li> <li><a href="#example-MultiReader" class="js-exampleHref">MultiReader</a></li> <li><a href="#example-MultiWriter" class="js-exampleHref">MultiWriter</a></li> <li><a href="#example-Pipe" class="js-exampleHref">Pipe</a></li> <li><a href="#example-ReadAll" class="js-exampleHref">ReadAll</a></li> <li><a href="#example-ReadAtLeast" class="js-exampleHref">ReadAtLeast</a></li> <li><a href="#example-ReadFull" class="js-exampleHref">ReadFull</a></li> <li><a href="#example-SectionReader" class="js-exampleHref">SectionReader</a></li> <li><a href="#example-SectionReader.Read" class="js-exampleHref">SectionReader.Read</a></li> <li><a href="#example-SectionReader.ReadAt" class="js-exampleHref">SectionReader.ReadAt</a></li> <li><a href="#example-SectionReader.Seek" class="js-exampleHref">SectionReader.Seek</a></li> <li><a href="#example-SectionReader.Size" class="js-exampleHref">SectionReader.Size</a></li> <li><a href="#example-TeeReader" class="js-exampleHref">TeeReader</a></li> <li><a href="#example-WriteString" class="js-exampleHref">WriteString</a></li> </ul> </section><h3 tabindex="-1" id="pkg-constants" class="Documentation-constantsHeader">Constants <a href="#pkg-constants" title="Go to Constants" aria-label="Go to Constants">露</a></h3> <section class="Documentation-constants"> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=21">View Source</a></span> <pre>const ( <span id="SeekStart" data-kind="constant"> SeekStart = 0 <span class="comment">// seek relative to the origin of the file</span> </span><span id="SeekCurrent" data-kind="constant"> SeekCurrent = 1 <span class="comment">// seek relative to the current offset</span> </span><span id="SeekEnd" data-kind="constant"> SeekEnd = 2 <span class="comment">// seek relative to the end</span> </span>)</pre> </div> <p>Seek whence values. </p> </section> <h3 tabindex="-1" id="pkg-variables" class="Documentation-variablesHeader">Variables <a href="#pkg-variables" title="Go to Variables" aria-label="Go to Variables">露</a></h3> <section class="Documentation-variables"> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=44">View Source</a></span> <pre><span id="EOF" data-kind="variable">var EOF = <a href="/errors">errors</a>.<a href="/errors#New">New</a>("EOF")</span></pre> </div> <p>EOF is the error returned by Read when no more input is available. (Read must return EOF itself, not an error wrapping EOF, because callers will test for EOF using ==.) Functions should return EOF only to signal a graceful end of input. If the EOF occurs unexpectedly in a structured data stream, the appropriate error is either <a href="#ErrUnexpectedEOF">ErrUnexpectedEOF</a> or some other error giving more detail. </p> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=36">View Source</a></span> <pre><span id="ErrClosedPipe" data-kind="variable">var ErrClosedPipe = <a href="/errors">errors</a>.<a href="/errors#New">New</a>("io: read/write on closed pipe")</span></pre> </div> <p>ErrClosedPipe is the error used for read or write operations on a closed pipe. </p> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=53">View Source</a></span> <pre><span id="ErrNoProgress" data-kind="variable">var ErrNoProgress = <a href="/errors">errors</a>.<a href="/errors#New">New</a>("multiple Read calls return no data or error")</span></pre> </div> <p>ErrNoProgress is returned by some clients of a <a href="#Reader">Reader</a> when many calls to Read have failed to return any data or error, usually the sign of a broken <a href="#Reader">Reader</a> implementation. </p> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=35">View Source</a></span> <pre><span id="ErrShortBuffer" data-kind="variable">var ErrShortBuffer = <a href="/errors">errors</a>.<a href="/errors#New">New</a>("short buffer")</span></pre> </div> <p>ErrShortBuffer means that a read required a longer buffer than was provided. </p> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=29">View Source</a></span> <pre><span id="ErrShortWrite" data-kind="variable">var ErrShortWrite = <a href="/errors">errors</a>.<a href="/errors#New">New</a>("short write")</span></pre> </div> <p>ErrShortWrite means that a write accepted fewer bytes than requested but failed to return an explicit error. </p> <div class="Documentation-declaration"> <span class="Documentation-declarationLink"><a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=48">View Source</a></span> <pre><span id="ErrUnexpectedEOF" data-kind="variable">var ErrUnexpectedEOF = <a href="/errors">errors</a>.<a href="/errors#New">New</a>("unexpected EOF")</span></pre> </div> <p>ErrUnexpectedEOF means that EOF was encountered in the middle of reading a fixed-size block or data structure. </p> </section> <h3 tabindex="-1" id="pkg-functions" class="Documentation-functionsHeader">Functions <a href="#pkg-functions" title="Go to Functions" aria-label="Go to Functions">露</a></h3> <section class="Documentation-functions"><div class="Documentation-function"> <h4 tabindex="-1" id="Copy" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=387">Copy</a> <a class="Documentation-idLink" href="#Copy" title="Go to Copy" aria-label="Go to Copy">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func Copy(dst <a href="#Writer">Writer</a>, src <a href="#Reader">Reader</a>) (written <a href="/builtin#int64">int64</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>Copy copies from src to dst until either EOF is reached on src or an error occurs. It returns the number of bytes copied and the first error encountered while copying, if any. </p><p>A successful Copy returns err == nil, not err == EOF. Because Copy is defined to read from src until EOF, it does not treat an EOF from Read as an error to be reported. </p><p>If src implements <a href="#WriterTo">WriterTo</a>, the copy is implemented by calling src.WriteTo(dst). Otherwise, if dst implements <a href="#ReaderFrom">ReaderFrom</a>, the copy is implemented by calling dst.ReadFrom(src). </p> <details tabindex="-1" id="example-Copy" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-Copy" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") if _, err := io.Copy(os.Stdout, r); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some io.Reader stream to be read </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-function"> <h4 tabindex="-1" id="CopyBuffer" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=398">CopyBuffer</a> <a class="Documentation-idLink" href="#CopyBuffer" title="Go to CopyBuffer" aria-label="Go to CopyBuffer">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.5</span> </span> </h4> <div class="Documentation-declaration"> <pre>func CopyBuffer(dst <a href="#Writer">Writer</a>, src <a href="#Reader">Reader</a>, buf []<a href="/builtin#byte">byte</a>) (written <a href="/builtin#int64">int64</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>CopyBuffer is identical to Copy except that it stages through the provided buffer (if one is required) rather than allocating a temporary one. If buf is nil, one is allocated; otherwise if it has zero length, CopyBuffer panics. </p><p>If either src implements <a href="#WriterTo">WriterTo</a> or dst implements <a href="#ReaderFrom">ReaderFrom</a>, buf will not be used to perform the copy. </p> <details tabindex="-1" id="example-CopyBuffer" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-CopyBuffer" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { r1 := strings.NewReader("first reader\n") r2 := strings.NewReader("second reader\n") buf := make([]byte, 8) // buf is used here... if _, err := io.CopyBuffer(os.Stdout, r1, buf); err != nil { log.Fatal(err) } // ... reused here also. No need to allocate an extra buffer. if _, err := io.CopyBuffer(os.Stdout, r2, buf); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">first reader second reader </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-function"> <h4 tabindex="-1" id="CopyN" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=363">CopyN</a> <a class="Documentation-idLink" href="#CopyN" title="Go to CopyN" aria-label="Go to CopyN">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func CopyN(dst <a href="#Writer">Writer</a>, src <a href="#Reader">Reader</a>, n <a href="/builtin#int64">int64</a>) (written <a href="/builtin#int64">int64</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>CopyN copies n bytes (or until an error) from src to dst. It returns the number of bytes copied and the earliest error encountered while copying. On return, written == n if and only if err == nil. </p><p>If dst implements <a href="#ReaderFrom">ReaderFrom</a>, the copy is implemented using it. </p> <details tabindex="-1" id="example-CopyN" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-CopyN" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read") if _, err := io.CopyN(os.Stdout, r, 4); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-function"> <h4 tabindex="-1" id="Pipe" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=195">Pipe</a> <a class="Documentation-idLink" href="#Pipe" title="Go to Pipe" aria-label="Go to Pipe">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func Pipe() (*<a href="#PipeReader">PipeReader</a>, *<a href="#PipeWriter">PipeWriter</a>)</pre> </div> <p>Pipe creates a synchronous in-memory pipe. It can be used to connect code expecting an <a href="#Reader">io.Reader</a> with code expecting an <a href="#Writer">io.Writer</a>. </p><p>Reads and Writes on the pipe are matched one to one except when multiple Reads are needed to consume a single Write. That is, each Write to the <a href="#PipeWriter">PipeWriter</a> blocks until it has satisfied one or more Reads from the <a href="#PipeReader">PipeReader</a> that fully consume the written data. The data is copied directly from the Write to the corresponding Read (or Reads); there is no internal buffering. </p><p>It is safe to call Read and Write in parallel with each other or with Close. Parallel calls to Read and parallel calls to Write are also safe: the individual calls will be gated sequentially. </p> <details tabindex="-1" id="example-Pipe" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-Pipe" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "log" "os" ) func main() { r, w := io.Pipe() go func() { fmt.Fprint(w, "some io.Reader stream to be read\n") w.Close() }() if _, err := io.Copy(os.Stdout, r); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some io.Reader stream to be read </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-function"> <h4 tabindex="-1" id="ReadAll" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=709">ReadAll</a> <a class="Documentation-idLink" href="#ReadAll" title="Go to ReadAll" aria-label="Go to ReadAll">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.16</span> </span> </h4> <div class="Documentation-declaration"> <pre>func ReadAll(r <a href="#Reader">Reader</a>) ([]<a href="/builtin#byte">byte</a>, <a href="/builtin#error">error</a>)</pre> </div> <p>ReadAll reads from r until an error or EOF and returns the data it read. A successful call returns err == nil, not err == EOF. Because ReadAll is defined to read from src until EOF, it does not treat an EOF from Read as an error to be reported. </p> <details tabindex="-1" id="example-ReadAll" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-ReadAll" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "log" "strings" ) func main() { r := strings.NewReader("Go is a general-purpose language designed with systems programming in mind.") b, err := io.ReadAll(r) if err != nil { log.Fatal(err) } fmt.Printf("%s", b) } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">Go is a general-purpose language designed with systems programming in mind. </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-function"> <h4 tabindex="-1" id="ReadAtLeast" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=329">ReadAtLeast</a> <a class="Documentation-idLink" href="#ReadAtLeast" title="Go to ReadAtLeast" aria-label="Go to ReadAtLeast">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func ReadAtLeast(r <a href="#Reader">Reader</a>, buf []<a href="/builtin#byte">byte</a>, min <a href="/builtin#int">int</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>ReadAtLeast reads from r into buf until it has read at least min bytes. It returns the number of bytes copied and an error if fewer bytes were read. The error is EOF only if no bytes were read. If an EOF happens after reading fewer than min bytes, ReadAtLeast returns <a href="#ErrUnexpectedEOF">ErrUnexpectedEOF</a>. If min is greater than the length of buf, ReadAtLeast returns <a href="#ErrShortBuffer">ErrShortBuffer</a>. On return, n >= min if and only if err == nil. If r returns an error having read at least min bytes, the error is dropped. </p> <details tabindex="-1" id="example-ReadAtLeast" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-ReadAtLeast" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "log" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") buf := make([]byte, 14) if _, err := io.ReadAtLeast(r, buf, 4); err != nil { log.Fatal(err) } fmt.Printf("%s\n", buf) // buffer smaller than minimal read size. shortBuf := make([]byte, 3) if _, err := io.ReadAtLeast(r, shortBuf, 4); err != nil { fmt.Println("error:", err) } // minimal read size bigger than io.Reader stream longBuf := make([]byte, 64) if _, err := io.ReadAtLeast(r, longBuf, 64); err != nil { fmt.Println("error:", err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some io.Reader error: short buffer error: unexpected EOF </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-function"> <h4 tabindex="-1" id="ReadFull" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=353">ReadFull</a> <a class="Documentation-idLink" href="#ReadFull" title="Go to ReadFull" aria-label="Go to ReadFull">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func ReadFull(r <a href="#Reader">Reader</a>, buf []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>ReadFull reads exactly len(buf) bytes from r into buf. It returns the number of bytes copied and an error if fewer bytes were read. The error is EOF only if no bytes were read. If an EOF happens after reading some but not all the bytes, ReadFull returns <a href="#ErrUnexpectedEOF">ErrUnexpectedEOF</a>. On return, n == len(buf) if and only if err == nil. If r returns an error having read at least len(buf) bytes, the error is dropped. </p> <details tabindex="-1" id="example-ReadFull" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-ReadFull" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "log" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") buf := make([]byte, 4) if _, err := io.ReadFull(r, buf); err != nil { log.Fatal(err) } fmt.Printf("%s\n", buf) // minimal read size bigger than io.Reader stream longBuf := make([]byte, 64) if _, err := io.ReadFull(r, longBuf); err != nil { fmt.Println("error:", err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some error: unexpected EOF </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-function"> <h4 tabindex="-1" id="WriteString" data-kind="function" class="Documentation-functionHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=314">WriteString</a> <a class="Documentation-idLink" href="#WriteString" title="Go to WriteString" aria-label="Go to WriteString">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func WriteString(w <a href="#Writer">Writer</a>, s <a href="/builtin#string">string</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>WriteString writes the contents of the string s to w, which accepts a slice of bytes. If w implements <a href="#StringWriter">StringWriter</a>, [StringWriter.WriteString] is invoked directly. Otherwise, [Writer.Write] is called exactly once. </p> <details tabindex="-1" id="example-WriteString" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-WriteString" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" ) func main() { if _, err := io.WriteString(os.Stdout, "Hello World"); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">Hello World </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div></section> <h3 tabindex="-1" id="pkg-types" class="Documentation-typesHeader">Types <a href="#pkg-types" title="Go to Types" aria-label="Go to Types">露</a></h3> <section class="Documentation-types"><div class="Documentation-type"> <h4 tabindex="-1" id="ByteReader" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=262">ByteReader</a> <a class="Documentation-idLink" href="#ByteReader" title="Go to ByteReader" aria-label="Go to ByteReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ByteReader interface { <span id="ByteReader.ReadByte" data-kind="method"> ReadByte() (<a href="/builtin#byte">byte</a>, <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>ByteReader is the interface that wraps the ReadByte method. </p><p>ReadByte reads and returns the next byte from the input or any error encountered. If ReadByte returns an error, no input byte was consumed, and the returned byte value is undefined. </p><p>ReadByte provides an efficient interface for byte-at-time processing. A <a href="#Reader">Reader</a> that does not implement ByteReader can be wrapped using bufio.NewReader to add this method. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ByteScanner" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=274">ByteScanner</a> <a class="Documentation-idLink" href="#ByteScanner" title="Go to ByteScanner" aria-label="Go to ByteScanner">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ByteScanner interface { <a href="#ByteReader">ByteReader</a> <span id="ByteScanner.UnreadByte" data-kind="method"> UnreadByte() <a href="/builtin#error">error</a> </span>}</pre> </div> <p>ByteScanner is the interface that adds the UnreadByte method to the basic ReadByte method. </p><p>UnreadByte causes the next call to ReadByte to return the last byte read. If the last operation was not a successful call to ReadByte, UnreadByte may return an error, unread the last byte read (or the byte prior to the last-unread byte), or (in implementations that support the <a href="#Seeker">Seeker</a> interface) seek to one byte before the current offset. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ByteWriter" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=280">ByteWriter</a> <a class="Documentation-idLink" href="#ByteWriter" title="Go to ByteWriter" aria-label="Go to ByteWriter">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.1</span> </span> </h4> <div class="Documentation-declaration"> <pre>type ByteWriter interface { <span id="ByteWriter.WriteByte" data-kind="method"> WriteByte(c <a href="/builtin#byte">byte</a>) <a href="/builtin#error">error</a> </span>}</pre> </div> <p>ByteWriter is the interface that wraps the WriteByte method. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="Closer" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=107">Closer</a> <a class="Documentation-idLink" href="#Closer" title="Go to Closer" aria-label="Go to Closer">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type Closer interface { <span id="Closer.Close" data-kind="method"> Close() <a href="/builtin#error">error</a> </span>}</pre> </div> <p>Closer is the interface that wraps the basic Close method. </p><p>The behavior of Close after the first call is undefined. Specific implementations may document their own behavior. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="LimitedReader" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=467">LimitedReader</a> <a class="Documentation-idLink" href="#LimitedReader" title="Go to LimitedReader" aria-label="Go to LimitedReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type LimitedReader struct { <span id="LimitedReader.R" data-kind="field"> R <a href="#Reader">Reader</a> <span class="comment">// underlying reader</span> </span><span id="LimitedReader.N" data-kind="field"> N <a href="/builtin#int64">int64</a> <span class="comment">// max bytes remaining</span> </span>}</pre> </div> <p>A LimitedReader reads from R but limits the amount of data returned to just N bytes. Each call to Read updates N to reflect the new amount remaining. Read returns EOF when N <= 0 or when the underlying R returns EOF. </p> <div class="Documentation-typeMethod"> <h4 tabindex="-1" id="LimitedReader.Read" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*LimitedReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=472">Read</a> <a class="Documentation-idLink" href="#LimitedReader.Read" title="Go to LimitedReader.Read" aria-label="Go to LimitedReader.Read">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (l *<a href="#LimitedReader">LimitedReader</a>) Read(p []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="OffsetWriter" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=570">OffsetWriter</a> <a class="Documentation-idLink" href="#OffsetWriter" title="Go to OffsetWriter" aria-label="Go to OffsetWriter">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.20</span> </span> </h4> <div class="Documentation-declaration"> <pre>type OffsetWriter struct { <span class="comment">// contains filtered or unexported fields</span> }</pre> </div> <p>An OffsetWriter maps writes at offset base to offset base+off in the underlying writer. </p> <div class="Documentation-typeFunc"> <h4 tabindex="-1" id="NewOffsetWriter" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=578">NewOffsetWriter</a> <a class="Documentation-idLink" href="#NewOffsetWriter" title="Go to NewOffsetWriter" aria-label="Go to NewOffsetWriter">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.20</span> </span> </h4> <div class="Documentation-declaration"> <pre>func NewOffsetWriter(w <a href="#WriterAt">WriterAt</a>, off <a href="/builtin#int64">int64</a>) *<a href="#OffsetWriter">OffsetWriter</a></pre> </div> <p>NewOffsetWriter returns an <a href="#OffsetWriter">OffsetWriter</a> that writes to w starting at offset off. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="OffsetWriter.Seek" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*OffsetWriter) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=597">Seek</a> <a class="Documentation-idLink" href="#OffsetWriter.Seek" title="Go to OffsetWriter.Seek" aria-label="Go to OffsetWriter.Seek">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.20</span> </span> </h4> <div class="Documentation-declaration"> <pre>func (o *<a href="#OffsetWriter">OffsetWriter</a>) Seek(offset <a href="/builtin#int64">int64</a>, whence <a href="/builtin#int">int</a>) (<a href="/builtin#int64">int64</a>, <a href="/builtin#error">error</a>)</pre> </div> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="OffsetWriter.Write" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*OffsetWriter) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=582">Write</a> <a class="Documentation-idLink" href="#OffsetWriter.Write" title="Go to OffsetWriter.Write" aria-label="Go to OffsetWriter.Write">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.20</span> </span> </h4> <div class="Documentation-declaration"> <pre>func (o *<a href="#OffsetWriter">OffsetWriter</a>) Write(p []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="OffsetWriter.WriteAt" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*OffsetWriter) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=588">WriteAt</a> <a class="Documentation-idLink" href="#OffsetWriter.WriteAt" title="Go to OffsetWriter.WriteAt" aria-label="Go to OffsetWriter.WriteAt">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.20</span> </span> </h4> <div class="Documentation-declaration"> <pre>func (o *<a href="#OffsetWriter">OffsetWriter</a>) WriteAt(p []<a href="/builtin#byte">byte</a>, off <a href="/builtin#int64">int64</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="PipeReader" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=126">PipeReader</a> <a class="Documentation-idLink" href="#PipeReader" title="Go to PipeReader" aria-label="Go to PipeReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type PipeReader struct { <span class="comment">// contains filtered or unexported fields</span> }</pre> </div> <p>A PipeReader is the read half of a pipe. </p> <div class="Documentation-typeMethod"> <h4 tabindex="-1" id="PipeReader.Close" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*PipeReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=139">Close</a> <a class="Documentation-idLink" href="#PipeReader.Close" title="Go to PipeReader.Close" aria-label="Go to PipeReader.Close">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (r *<a href="#PipeReader">PipeReader</a>) Close() <a href="/builtin#error">error</a></pre> </div> <p>Close closes the reader; subsequent writes to the write half of the pipe will return the error <a href="#ErrClosedPipe">ErrClosedPipe</a>. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="PipeReader.CloseWithError" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*PipeReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=148">CloseWithError</a> <a class="Documentation-idLink" href="#PipeReader.CloseWithError" title="Go to PipeReader.CloseWithError" aria-label="Go to PipeReader.CloseWithError">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (r *<a href="#PipeReader">PipeReader</a>) CloseWithError(err <a href="/builtin#error">error</a>) <a href="/builtin#error">error</a></pre> </div> <p>CloseWithError closes the reader; subsequent writes to the write half of the pipe will return the error err. </p><p>CloseWithError never overwrites the previous error if it exists and always returns nil. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="PipeReader.Read" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*PipeReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=133">Read</a> <a class="Documentation-idLink" href="#PipeReader.Read" title="Go to PipeReader.Read" aria-label="Go to PipeReader.Read">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (r *<a href="#PipeReader">PipeReader</a>) Read(data []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>Read implements the standard Read interface: it reads data from the pipe, blocking until a writer arrives or the write end is closed. If the write end is closed with an error, that error is returned as err; otherwise err is EOF. </p> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="PipeWriter" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=153">PipeWriter</a> <a class="Documentation-idLink" href="#PipeWriter" title="Go to PipeWriter" aria-label="Go to PipeWriter">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type PipeWriter struct { <span class="comment">// contains filtered or unexported fields</span> }</pre> </div> <p>A PipeWriter is the write half of a pipe. </p> <div class="Documentation-typeMethod"> <h4 tabindex="-1" id="PipeWriter.Close" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*PipeWriter) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=166">Close</a> <a class="Documentation-idLink" href="#PipeWriter.Close" title="Go to PipeWriter.Close" aria-label="Go to PipeWriter.Close">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (w *<a href="#PipeWriter">PipeWriter</a>) Close() <a href="/builtin#error">error</a></pre> </div> <p>Close closes the writer; subsequent reads from the read half of the pipe will return no bytes and EOF. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="PipeWriter.CloseWithError" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*PipeWriter) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=176">CloseWithError</a> <a class="Documentation-idLink" href="#PipeWriter.CloseWithError" title="Go to PipeWriter.CloseWithError" aria-label="Go to PipeWriter.CloseWithError">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (w *<a href="#PipeWriter">PipeWriter</a>) CloseWithError(err <a href="/builtin#error">error</a>) <a href="/builtin#error">error</a></pre> </div> <p>CloseWithError closes the writer; subsequent reads from the read half of the pipe will return no bytes and the error err, or EOF if err is nil. </p><p>CloseWithError never overwrites the previous error if it exists and always returns nil. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="PipeWriter.Write" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*PipeWriter) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go;l=160">Write</a> <a class="Documentation-idLink" href="#PipeWriter.Write" title="Go to PipeWriter.Write" aria-label="Go to PipeWriter.Write">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (w *<a href="#PipeWriter">PipeWriter</a>) Write(data []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <p>Write implements the standard Write interface: it writes data to the pipe, blocking until one or more readers have consumed all the data or the read end is closed. If the read end is closed with an error, that err is returned as err; otherwise err is <a href="#ErrClosedPipe">ErrClosedPipe</a>. </p> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReadCloser" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=137">ReadCloser</a> <a class="Documentation-idLink" href="#ReadCloser" title="Go to ReadCloser" aria-label="Go to ReadCloser">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ReadCloser interface { <a href="#Reader">Reader</a> <a href="#Closer">Closer</a> }</pre> </div> <p>ReadCloser is the interface that groups the basic Read and Close methods. </p> <div class="Documentation-typeFunc"> <h4 tabindex="-1" id="NopCloser" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=682">NopCloser</a> <a class="Documentation-idLink" href="#NopCloser" title="Go to NopCloser" aria-label="Go to NopCloser">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.16</span> </span> </h4> <div class="Documentation-declaration"> <pre>func NopCloser(r <a href="#Reader">Reader</a>) <a href="#ReadCloser">ReadCloser</a></pre> </div> <p>NopCloser returns a <a href="#ReadCloser">ReadCloser</a> with a no-op Close method wrapping the provided <a href="#Reader">Reader</a> r. If r implements <a href="#WriterTo">WriterTo</a>, the returned <a href="#ReadCloser">ReadCloser</a> will implement <a href="#WriterTo">WriterTo</a> by forwarding calls to r. </p> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReadSeekCloser" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=163">ReadSeekCloser</a> <a class="Documentation-idLink" href="#ReadSeekCloser" title="Go to ReadSeekCloser" aria-label="Go to ReadSeekCloser">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.16</span> </span> </h4> <div class="Documentation-declaration"> <pre>type ReadSeekCloser interface { <a href="#Reader">Reader</a> <a href="#Seeker">Seeker</a> <a href="#Closer">Closer</a> }</pre> </div> <p>ReadSeekCloser is the interface that groups the basic Read, Seek and Close methods. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReadSeeker" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=156">ReadSeeker</a> <a class="Documentation-idLink" href="#ReadSeeker" title="Go to ReadSeeker" aria-label="Go to ReadSeeker">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ReadSeeker interface { <a href="#Reader">Reader</a> <a href="#Seeker">Seeker</a> }</pre> </div> <p>ReadSeeker is the interface that groups the basic Read and Seek methods. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReadWriteCloser" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=149">ReadWriteCloser</a> <a class="Documentation-idLink" href="#ReadWriteCloser" title="Go to ReadWriteCloser" aria-label="Go to ReadWriteCloser">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ReadWriteCloser interface { <a href="#Reader">Reader</a> <a href="#Writer">Writer</a> <a href="#Closer">Closer</a> }</pre> </div> <p>ReadWriteCloser is the interface that groups the basic Read, Write and Close methods. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReadWriteSeeker" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=176">ReadWriteSeeker</a> <a class="Documentation-idLink" href="#ReadWriteSeeker" title="Go to ReadWriteSeeker" aria-label="Go to ReadWriteSeeker">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ReadWriteSeeker interface { <a href="#Reader">Reader</a> <a href="#Writer">Writer</a> <a href="#Seeker">Seeker</a> }</pre> </div> <p>ReadWriteSeeker is the interface that groups the basic Read, Write and Seek methods. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReadWriter" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=131">ReadWriter</a> <a class="Documentation-idLink" href="#ReadWriter" title="Go to ReadWriter" aria-label="Go to ReadWriter">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ReadWriter interface { <a href="#Reader">Reader</a> <a href="#Writer">Writer</a> }</pre> </div> <p>ReadWriter is the interface that groups the basic Read and Write methods. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="Reader" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=86">Reader</a> <a class="Documentation-idLink" href="#Reader" title="Go to Reader" aria-label="Go to Reader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type Reader interface { <span id="Reader.Read" data-kind="method"> Read(p []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>Reader is the interface that wraps the basic Read method. </p><p>Read reads up to len(p) bytes into p. It returns the number of bytes read (0 <= n <= len(p)) and any error encountered. Even if Read returns n < len(p), it may use all of p as scratch space during the call. If some data is available but not len(p) bytes, Read conventionally returns what is available instead of waiting for more. </p><p>When Read encounters an error or end-of-file condition after successfully reading n > 0 bytes, it returns the number of bytes read. It may return the (non-nil) error from the same call or return the error (and n == 0) from a subsequent call. An instance of this general case is that a Reader returning a non-zero number of bytes at the end of the input stream may return either err == EOF or err == nil. The next Read should return 0, EOF. </p><p>Callers should always process the n > 0 bytes returned before considering the error err. Doing so correctly handles I/O errors that happen after reading some bytes and also both of the allowed EOF behaviors. </p><p>If len(p) == 0, Read should always return n == 0. It may return a non-nil error if some error condition is known, such as EOF. </p><p>Implementations of Read are discouraged from returning a zero byte count with a nil error, except when len(p) == 0. Callers should treat a return of 0 and nil as indicating that nothing happened; in particular it does not indicate EOF. </p><p>Implementations must not retain p. </p> <div class="Documentation-typeFunc"> <h4 tabindex="-1" id="LimitReader" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=461">LimitReader</a> <a class="Documentation-idLink" href="#LimitReader" title="Go to LimitReader" aria-label="Go to LimitReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func LimitReader(r <a href="#Reader">Reader</a>, n <a href="/builtin#int64">int64</a>) <a href="#Reader">Reader</a></pre> </div> <p>LimitReader returns a Reader that reads from r but stops with EOF after n bytes. The underlying implementation is a *LimitedReader. </p> <details tabindex="-1" id="example-LimitReader" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-LimitReader" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") lr := io.LimitReader(r, 4) if _, err := io.Copy(os.Stdout, lr); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-typeFunc"> <h4 tabindex="-1" id="MultiReader" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/multi.go;l=73">MultiReader</a> <a class="Documentation-idLink" href="#MultiReader" title="Go to MultiReader" aria-label="Go to MultiReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func MultiReader(readers ...<a href="#Reader">Reader</a>) <a href="#Reader">Reader</a></pre> </div> <p>MultiReader returns a Reader that's the logical concatenation of the provided input readers. They're read sequentially. Once all inputs have returned EOF, Read will return EOF. If any of the readers return a non-nil, non-EOF error, Read will return that error. </p> <details tabindex="-1" id="example-MultiReader" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-MultiReader" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { r1 := strings.NewReader("first reader ") r2 := strings.NewReader("second reader ") r3 := strings.NewReader("third reader\n") r := io.MultiReader(r1, r2, r3) if _, err := io.Copy(os.Stdout, r); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">first reader second reader third reader </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-typeFunc"> <h4 tabindex="-1" id="TeeReader" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=618">TeeReader</a> <a class="Documentation-idLink" href="#TeeReader" title="Go to TeeReader" aria-label="Go to TeeReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func TeeReader(r <a href="#Reader">Reader</a>, w <a href="#Writer">Writer</a>) <a href="#Reader">Reader</a></pre> </div> <p>TeeReader returns a <a href="#Reader">Reader</a> that writes to w what it reads from r. All reads from r performed through it are matched with corresponding writes to w. There is no internal buffering - the write must complete before the read completes. Any error encountered while writing is reported as a read error. </p> <details tabindex="-1" id="example-TeeReader" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-TeeReader" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { var r io.Reader = strings.NewReader("some io.Reader stream to be read\n") r = io.TeeReader(r, os.Stdout) // Everything read from r will be copied to stdout. if _, err := io.ReadAll(r); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some io.Reader stream to be read </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReaderAt" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=230">ReaderAt</a> <a class="Documentation-idLink" href="#ReaderAt" title="Go to ReaderAt" aria-label="Go to ReaderAt">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ReaderAt interface { <span id="ReaderAt.ReadAt" data-kind="method"> ReadAt(p []<a href="/builtin#byte">byte</a>, off <a href="/builtin#int64">int64</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>ReaderAt is the interface that wraps the basic ReadAt method. </p><p>ReadAt reads len(p) bytes into p starting at offset off in the underlying input source. It returns the number of bytes read (0 <= n <= len(p)) and any error encountered. </p><p>When ReadAt returns n < len(p), it returns a non-nil error explaining why more bytes were not returned. In this respect, ReadAt is stricter than Read. </p><p>Even if ReadAt returns n < len(p), it may use all of p as scratch space during the call. If some data is available but not len(p) bytes, ReadAt blocks until either all the data is available or an error occurs. In this respect ReadAt is different from Read. </p><p>If the n = len(p) bytes returned by ReadAt are at the end of the input source, ReadAt may return either err == EOF or err == nil. </p><p>If ReadAt is reading from an input source with a seek offset, ReadAt should not affect nor be affected by the underlying seek offset. </p><p>Clients of ReadAt can execute parallel ReadAt calls on the same input source. </p><p>Implementations must not retain p. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="ReaderFrom" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=189">ReaderFrom</a> <a class="Documentation-idLink" href="#ReaderFrom" title="Go to ReaderFrom" aria-label="Go to ReaderFrom">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type ReaderFrom interface { <span id="ReaderFrom.ReadFrom" data-kind="method"> ReadFrom(r <a href="#Reader">Reader</a>) (n <a href="/builtin#int64">int64</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>ReaderFrom is the interface that wraps the ReadFrom method. </p><p>ReadFrom reads data from r until EOF or error. The return value n is the number of bytes read. Any error except EOF encountered during the read is also returned. </p><p>The <a href="#Copy">Copy</a> function uses <a href="#ReaderFrom">ReaderFrom</a> if available. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="RuneReader" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=289">RuneReader</a> <a class="Documentation-idLink" href="#RuneReader" title="Go to RuneReader" aria-label="Go to RuneReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type RuneReader interface { <span id="RuneReader.ReadRune" data-kind="method"> ReadRune() (r <a href="/builtin#rune">rune</a>, size <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>RuneReader is the interface that wraps the ReadRune method. </p><p>ReadRune reads a single encoded Unicode character and returns the rune and its size in bytes. If no character is available, err will be set. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="RuneScanner" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=301">RuneScanner</a> <a class="Documentation-idLink" href="#RuneScanner" title="Go to RuneScanner" aria-label="Go to RuneScanner">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type RuneScanner interface { <a href="#RuneReader">RuneReader</a> <span id="RuneScanner.UnreadRune" data-kind="method"> UnreadRune() <a href="/builtin#error">error</a> </span>}</pre> </div> <p>RuneScanner is the interface that adds the UnreadRune method to the basic ReadRune method. </p><p>UnreadRune causes the next call to ReadRune to return the last rune read. If the last operation was not a successful call to ReadRune, UnreadRune may return an error, unread the last rune read (or the rune prior to the last-unread rune), or (in implementations that support the <a href="#Seeker">Seeker</a> interface) seek to the start of the rune before the current offset. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="SectionReader" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=501">SectionReader</a> <a class="Documentation-idLink" href="#SectionReader" title="Go to SectionReader" aria-label="Go to SectionReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type SectionReader struct { <span class="comment">// contains filtered or unexported fields</span> }</pre> </div> <p>SectionReader implements Read, Seek, and ReadAt on a section of an underlying <a href="#ReaderAt">ReaderAt</a>. </p> <details tabindex="-1" id="example-SectionReader" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-SectionReader" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") s := io.NewSectionReader(r, 5, 17) if _, err := io.Copy(os.Stdout, s); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">io.Reader stream </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> <div class="Documentation-typeFunc"> <h4 tabindex="-1" id="NewSectionReader" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=486">NewSectionReader</a> <a class="Documentation-idLink" href="#NewSectionReader" title="Go to NewSectionReader" aria-label="Go to NewSectionReader">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func NewSectionReader(r <a href="#ReaderAt">ReaderAt</a>, off <a href="/builtin#int64">int64</a>, n <a href="/builtin#int64">int64</a>) *<a href="#SectionReader">SectionReader</a></pre> </div> <p>NewSectionReader returns a <a href="#SectionReader">SectionReader</a> that reads from r starting at offset off and stops with EOF after n bytes. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="SectionReader.Outer" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*SectionReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=565">Outer</a> <a class="Documentation-idLink" href="#SectionReader.Outer" title="Go to SectionReader.Outer" aria-label="Go to SectionReader.Outer">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.22.0</span> </span> </h4> <div class="Documentation-declaration"> <pre>func (s *<a href="#SectionReader">SectionReader</a>) Outer() (r <a href="#ReaderAt">ReaderAt</a>, off <a href="/builtin#int64">int64</a>, n <a href="/builtin#int64">int64</a>)</pre> </div> <p>Outer returns the underlying <a href="#ReaderAt">ReaderAt</a> and offsets for the section. </p><p>The returned values are the same that were passed to <a href="#NewSectionReader">NewSectionReader</a> when the <a href="#SectionReader">SectionReader</a> was created. </p> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="SectionReader.Read" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*SectionReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=509">Read</a> <a class="Documentation-idLink" href="#SectionReader.Read" title="Go to SectionReader.Read" aria-label="Go to SectionReader.Read">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (s *<a href="#SectionReader">SectionReader</a>) Read(p []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <details tabindex="-1" id="example-SectionReader.Read" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-SectionReader.Read" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "log" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") s := io.NewSectionReader(r, 5, 17) buf := make([]byte, 9) if _, err := s.Read(buf); err != nil { log.Fatal(err) } fmt.Printf("%s\n", buf) } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">io.Reader </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="SectionReader.ReadAt" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*SectionReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=542">ReadAt</a> <a class="Documentation-idLink" href="#SectionReader.ReadAt" title="Go to SectionReader.ReadAt" aria-label="Go to SectionReader.ReadAt">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (s *<a href="#SectionReader">SectionReader</a>) ReadAt(p []<a href="/builtin#byte">byte</a>, off <a href="/builtin#int64">int64</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>)</pre> </div> <details tabindex="-1" id="example-SectionReader.ReadAt" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-SectionReader.ReadAt" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "log" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") s := io.NewSectionReader(r, 5, 17) buf := make([]byte, 6) if _, err := s.ReadAt(buf, 10); err != nil { log.Fatal(err) } fmt.Printf("%s\n", buf) } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">stream </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="SectionReader.Seek" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*SectionReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=524">Seek</a> <a class="Documentation-idLink" href="#SectionReader.Seek" title="Go to SectionReader.Seek" aria-label="Go to SectionReader.Seek">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (s *<a href="#SectionReader">SectionReader</a>) Seek(offset <a href="/builtin#int64">int64</a>, whence <a href="/builtin#int">int</a>) (<a href="/builtin#int64">int64</a>, <a href="/builtin#error">error</a>)</pre> </div> <details tabindex="-1" id="example-SectionReader.Seek" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-SectionReader.Seek" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "io" "log" "os" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") s := io.NewSectionReader(r, 5, 17) if _, err := s.Seek(10, io.SeekStart); err != nil { log.Fatal(err) } if _, err := io.Copy(os.Stdout, s); err != nil { log.Fatal(err) } } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">stream </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div><div class="Documentation-typeMethod"> <h4 tabindex="-1" id="SectionReader.Size" data-kind="method" class="Documentation-typeMethodHeader"> <span>func (*SectionReader) <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=559">Size</a> <a class="Documentation-idLink" href="#SectionReader.Size" title="Go to SectionReader.Size" aria-label="Go to SectionReader.Size">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func (s *<a href="#SectionReader">SectionReader</a>) Size() <a href="/builtin#int64">int64</a></pre> </div> <p>Size returns the size of the section in bytes. </p> <details tabindex="-1" id="example-SectionReader.Size" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-SectionReader.Size" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") s := io.NewSectionReader(r, 5, 17) fmt.Println(s.Size()) } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">17 </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="Seeker" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=126">Seeker</a> <a class="Documentation-idLink" href="#Seeker" title="Go to Seeker" aria-label="Go to Seeker">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type Seeker interface { <span id="Seeker.Seek" data-kind="method"> Seek(offset <a href="/builtin#int64">int64</a>, whence <a href="/builtin#int">int</a>) (<a href="/builtin#int64">int64</a>, <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>Seeker is the interface that wraps the basic Seek method. </p><p>Seek sets the offset for the next Read or Write to offset, interpreted according to whence: <a href="#SeekStart">SeekStart</a> means relative to the start of the file, <a href="#SeekCurrent">SeekCurrent</a> means relative to the current offset, and <a href="#SeekEnd">SeekEnd</a> means relative to the end (for example, offset = -2 specifies the penultimate byte of the file). Seek returns the new offset relative to the start of the file or an error, if any. </p><p>Seeking to an offset before the start of the file is an error. Seeking to any positive offset may be allowed, but if the new offset exceeds the size of the underlying object the behavior of subsequent I/O operations is implementation-dependent. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="StringWriter" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=307">StringWriter</a> <a class="Documentation-idLink" href="#StringWriter" title="Go to StringWriter" aria-label="Go to StringWriter">露</a></span> <span class="Documentation-sinceVersion"> <span class="Documentation-sinceVersionLabel">added in</span> <span class="Documentation-sinceVersionVersion">go1.12</span> </span> </h4> <div class="Documentation-declaration"> <pre>type StringWriter interface { <span id="StringWriter.WriteString" data-kind="method"> WriteString(s <a href="/builtin#string">string</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>StringWriter is the interface that wraps the WriteString method. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="WriteCloser" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=143">WriteCloser</a> <a class="Documentation-idLink" href="#WriteCloser" title="Go to WriteCloser" aria-label="Go to WriteCloser">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type WriteCloser interface { <a href="#Writer">Writer</a> <a href="#Closer">Closer</a> }</pre> </div> <p>WriteCloser is the interface that groups the basic Write and Close methods. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="WriteSeeker" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=170">WriteSeeker</a> <a class="Documentation-idLink" href="#WriteSeeker" title="Go to WriteSeeker" aria-label="Go to WriteSeeker">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type WriteSeeker interface { <a href="#Writer">Writer</a> <a href="#Seeker">Seeker</a> }</pre> </div> <p>WriteSeeker is the interface that groups the basic Write and Seek methods. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="Writer" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=99">Writer</a> <a class="Documentation-idLink" href="#Writer" title="Go to Writer" aria-label="Go to Writer">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type Writer interface { <span id="Writer.Write" data-kind="method"> Write(p []<a href="/builtin#byte">byte</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>Writer is the interface that wraps the basic Write method. </p><p>Write writes len(p) bytes from p to the underlying data stream. It returns the number of bytes written from p (0 <= n <= len(p)) and any error encountered that caused the write to stop early. Write must return a non-nil error if it returns n < len(p). Write must not modify the slice data, even temporarily. </p><p>Implementations must not retain p. </p> <div class="Documentation-typeVariable"> <div class="Documentation-declaration"> <pre><span id="Discard" data-kind="variable">var Discard <a href="#Writer">Writer</a> = discard{}</span></pre> </div> <p>Discard is a <a href="#Writer">Writer</a> on which all Write calls succeed without doing anything. </p> </div><div class="Documentation-typeFunc"> <h4 tabindex="-1" id="MultiWriter" data-kind="function" class="Documentation-typeFuncHeader"> <span>func <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/multi.go;l=127">MultiWriter</a> <a class="Documentation-idLink" href="#MultiWriter" title="Go to MultiWriter" aria-label="Go to MultiWriter">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>func MultiWriter(writers ...<a href="#Writer">Writer</a>) <a href="#Writer">Writer</a></pre> </div> <p>MultiWriter creates a writer that duplicates its writes to all the provided writers, similar to the Unix tee(1) command. </p><p>Each write is written to each listed writer, one at a time. If a listed writer returns an error, that overall write operation stops and returns the error; it does not continue down the list. </p> <details tabindex="-1" id="example-MultiWriter" class="Documentation-exampleDetails js-exampleContainer"> <summary class="Documentation-exampleDetailsHeader">Example <a href="#example-MultiWriter" title="Go to Example" aria-label="Go to Example">露</a></summary> <div class="Documentation-exampleDetailsBody"> <pre class="Documentation-exampleCode"> package main import ( "fmt" "io" "log" "strings" ) func main() { r := strings.NewReader("some io.Reader stream to be read\n") var buf1, buf2 strings.Builder w := io.MultiWriter(&buf1, &buf2) if _, err := io.Copy(w, r); err != nil { log.Fatal(err) } fmt.Print(buf1.String()) fmt.Print(buf2.String()) } </pre> <pre><span class="Documentation-exampleOutputLabel">Output:</span> <span class="Documentation-exampleOutput">some io.Reader stream to be read some io.Reader stream to be read </span></pre> </div> <div class="Documentation-exampleButtonsContainer"> <p class="Documentation-exampleError" role="alert" aria-atomic="true"></p> <button class="Documentation-exampleShareButton" aria-label="Share Code">Share</button> <button class="Documentation-exampleFormatButton" aria-label="Format Code">Format</button> <button class="Documentation-exampleRunButton" aria-label="Run Code">Run</button> </div></details> </div> </div><div class="Documentation-type"> <h4 tabindex="-1" id="WriterAt" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=249">WriterAt</a> <a class="Documentation-idLink" href="#WriterAt" title="Go to WriterAt" aria-label="Go to WriterAt">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type WriterAt interface { <span id="WriterAt.WriteAt" data-kind="method"> WriteAt(p []<a href="/builtin#byte">byte</a>, off <a href="/builtin#int64">int64</a>) (n <a href="/builtin#int">int</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>WriterAt is the interface that wraps the basic WriteAt method. </p><p>WriteAt writes len(p) bytes from p to the underlying data stream at offset off. It returns the number of bytes written from p (0 <= n <= len(p)) and any error encountered that caused the write to stop early. WriteAt must return a non-nil error if it returns n < len(p). </p><p>If WriteAt is writing to a destination with a seek offset, WriteAt should not affect nor be affected by the underlying seek offset. </p><p>Clients of WriteAt can execute parallel WriteAt calls on the same destination if the ranges do not overlap. </p><p>Implementations must not retain p. </p> </div><div class="Documentation-type"> <h4 tabindex="-1" id="WriterTo" data-kind="type" class="Documentation-typeHeader"> <span>type <a class="Documentation-source" href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go;l=200">WriterTo</a> <a class="Documentation-idLink" href="#WriterTo" title="Go to WriterTo" aria-label="Go to WriterTo">露</a></span> <span class="Documentation-sinceVersion"> </span> </h4> <div class="Documentation-declaration"> <pre>type WriterTo interface { <span id="WriterTo.WriteTo" data-kind="method"> WriteTo(w <a href="#Writer">Writer</a>) (n <a href="/builtin#int64">int64</a>, err <a href="/builtin#error">error</a>) </span>}</pre> </div> <p>WriterTo is the interface that wraps the WriteTo method. </p><p>WriteTo writes data to w until there's no more data to write or when an error occurs. The return value n is the number of bytes written. Any error encountered during the write is also returned. </p><p>The Copy function uses WriterTo if available. </p> </div></section></div> </div> </div> <div class="UnitFiles js-unitFiles"> <h2 class="UnitFiles-title" id="section-sourcefiles"> <img class="go-Icon" height="24" width="24" src="/static/shared/icon/insert_drive_file_gm_grey_24dp.svg" alt=""> Source Files <a class="UnitFiles-idLink" href="#section-sourcefiles" title="Go to Source Files" aria-label="Go to Source Files">露</a> </h2> <div class="UnitFiles-titleLink"> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/io" target="_blank" rel="noopener">View all Source files</a> </div> <div> <ul class="UnitFiles-fileList"><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/io.go" target="_blank" rel="noopener" title="io.go">io.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/multi.go" target="_blank" rel="noopener" title="multi.go">multi.go</a> </li><li> <a href="https://cs.opensource.google/go/go/+/go1.24.1:src/io/pipe.go" target="_blank" rel="noopener" title="pipe.go">pipe.go</a> </li></ul> </div> </div> <div class="UnitDirectories js-unitDirectories"> <h2 class="UnitDirectories-title" id="section-directories"> <img class="go-Icon" height="24" width="24" src="/static/shared/icon/folder_gm_grey_24dp.svg" alt=""> Directories <a class="UnitDirectories-idLink" href="#section-directories" title="Go to Directories" aria-label="Go to Directories">露</a> </h2> <div class="UnitDirectories-toggles"> <div class="UnitDirectories-toggleButtons"> <button class="js-showInternalDirectories" data-test-id="internal-directories-toggle" data-gtmc="directories button" aria-label="Show Internal Directories"> Show internal </button> <button class="js-expandAllDirectories" data-test-id="directories-toggle" data-gtmc="directories button" aria-label="Expand All Directories"> Expand all </button> </div> </div> <table class="UnitDirectories-table UnitDirectories-table--tree js-expandableTable" data-test-id="UnitDirectories-table"> <tr class="UnitDirectories-tableHeader UnitDirectories-tableHeader--tree"> <th>Path</th> <th class="UnitDirectories-desktopSynopsis">Synopsis</th> </tr> <tr class=""> <td data-id="fs" data-aria-owns=""> <div class="UnitDirectories-pathCell"> <div><a href="/io/fs@go1.24.1">fs</a> </div> <div class="UnitDirectories-mobileSynopsis">Package fs defines basic interfaces to a file system.</div> </div> </td> <td class="UnitDirectories-desktopSynopsis">Package fs defines basic interfaces to a file system.</td></tr></tr> <tr class=""> <td data-id="ioutil" data-aria-owns=""> <div class="UnitDirectories-pathCell"> <div><a href="/io/ioutil@go1.24.1">ioutil</a> </div> <div class="UnitDirectories-mobileSynopsis">Package ioutil implements some I/O utility functions.</div> </div> </td> <td class="UnitDirectories-desktopSynopsis">Package ioutil implements some I/O utility functions.</td></tr></tr> </table> </div> 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