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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><meta name="viewport" content="width=device-width, initial-scale=0.8"/><title>13.1.6 String Ports</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="icons.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">►</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x">The Racket Reference</a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="model.html" class="tocviewlink" data-pltdoc="x">Language Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewlink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="tocviewlink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr><tr><td align="right">12 </td><td><a href="Macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">13 </td><td><a href="input-and-output.html" class="tocviewselflink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr><tr><td align="right">15 </td><td><a href="os.html" class="tocviewlink" data-pltdoc="x">Operating System</a></td></tr><tr><td align="right">16 </td><td><a href="memory.html" class="tocviewlink" data-pltdoc="x">Memory Management</a></td></tr><tr><td align="right">17 </td><td><a href="unsafe.html" class="tocviewlink" data-pltdoc="x">Unsafe Operations</a></td></t
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input <a href="stringport.html#%28tech._string._port%29" class="techoutside" data-pltdoc="x"><span class="techinside">string port</span></a> can be created from either a <a href="bytestrings.html#%28tech._byte._string%29" class="techoutside" data-pltdoc="x"><span class="techinside">byte string</span></a>
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or a <a href="strings.html#%28tech._string%29" class="techoutside" data-pltdoc="x"><span class="techinside">string</span></a>; in the latter case, the <a href="strings.html#%28tech._string%29" class="techoutside" data-pltdoc="x"><span class="techinside">string</span></a> is effectively
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converted to a <a href="bytestrings.html#%28tech._byte._string%29" class="techoutside" data-pltdoc="x"><span class="techinside">byte string</span></a> using <span class="RktSym"><a href="bytestrings.html#%28def._%28%28quote._~23~25kernel%29._string-~3ebytes%2Futf-8%29%29" class="RktValLink" data-pltdoc="x">string->bytes/utf-8</a></span>. An
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output <a href="stringport.html#%28tech._string._port%29" class="techoutside" data-pltdoc="x"><span class="techinside">string port</span></a> collects output into a <a href="bytestrings.html#%28tech._byte._string%29" class="techoutside" data-pltdoc="x"><span class="techinside">byte string</span></a>, but
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<span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-string%29%29" class="RktValLink" data-pltdoc="x">get-output-string</a></span> conveniently converts the accumulated bytes
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to a <a href="strings.html#%28tech._string%29" class="techoutside" data-pltdoc="x"><span class="techinside">string</span></a>.</p><p>Input and output <a href="stringport.html#%28tech._string._port%29" class="techoutside" data-pltdoc="x"><span class="techinside">string ports</span></a> do not need to be explicitly
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closed. The <span class="RktSym"><a href="port-buffers.html#%28def._%28%28quote._~23~25kernel%29._file-position%29%29" class="RktValLink" data-pltdoc="x">file-position</a></span> procedure works for <a href="stringport.html#%28tech._string._port%29" class="techoutside" data-pltdoc="x"><span class="techinside">string
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ports</span></a> in position-setting mode.</p><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p><span class="imageleft"><img src="magnify.png" alt="+" width="24" height="24"/></span><a href="bytestrings.html" data-pltdoc="x">Byte Strings</a> also provides information on bytestrings.</p></blockquote></blockquote></blockquote><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._string-port~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._string-port~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">string-port?</a></span></span><span class="hspace"> </span><span class="RktVar">p</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._boolean~3f%29%29" class="RktValLink" data-pltdoc="x">boolean?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">p</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="port-ops.html#%28def._%28%28lib._racket%2Fprivate%2Fmisc..rkt%29._port~3f%29%29" class="RktValLink" data-pltdoc="x">port?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns <span class="RktVal">#t</span> if <span class="RktVar">p</span> is a <a href="stringport.html#%28tech._string._port%29" class="techoutside" data-pltdoc="x"><span class="techinside">string port</span></a>, <span class="RktVal">#f</span>
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otherwise.</div></p><p class="SHistory">Added in version 6.0.1.6 of package <span class="stt">base</span>.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._open-input-bytes))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-bytes%29%29" class="RktValDef RktValLink" data-pltdoc="x">open-input-bytes</a></span></span><span class="hspace"> </span><span class="RktVar">bstr</span><span class="hspace"> </span><span class="RktOpt">[</span><span class="RktVar">name</span><span class="RktOpt">]</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="port-ops.html#%28def._%28%28quote._~23~25kernel%29._input-port~3f%29%29" class="RktValLink" data-pltdoc="x">input-port?</a></span><span class="hspace"> </span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._string-port~3f%29%29" class="RktValLink" data-pltdoc="x">string-port?</a></span><span class="RktPn">)</span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">bstr</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="bytestrings.html#%28def._%28%28quote._~23~25kernel%29._bytes~3f%29%29" class="RktValLink" data-pltdoc="x">bytes?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">name</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span><span class="hspace"> </span>=<span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">string</span></td></tr></table></blockquote></div><div class="SIntrapara">Creates an input <a href="stringport.html#%28tech._string._port%29" class="techoutside" data-pltdoc="x"><span class="techinside">string port</span></a> that reads characters from
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<span class="RktVar">bstr</span> (see <a href="bytestrings.html" data-pltdoc="x">Byte Strings</a>). Modifying <span class="RktVar">bstr</span>
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afterward does not affect the byte stream produced by the port. The
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optional <span class="RktVar">name</span> argument is used as the name for the returned
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port.</div></p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">sp</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-bytes%29%29" class="RktValLink" data-pltdoc="x">open-input-bytes</a></span><span class="hspace"> </span><span class="RktVal">#"(apples 42 day)"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">sexp1</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%29%29" class="RktValLink" data-pltdoc="x">read</a></span><span class="hspace"> </span><span class="RktSym">sp</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28lib._racket%2Flist..rkt%29._first%29%29" class="RktValLink" data-pltdoc="x">first</a></span><span class="hspace"> </span><span class="RktSym">sexp1</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'apples</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28lib._racket%2Flist..rkt%29._rest%29%29" class="RktValLink" data-pltdoc="x">rest</a></span><span class="hspace"> </span><span class="RktSym">sexp1</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(42 day)</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._read-line%29%29" class="RktValLink" data-pltdoc="x">read-line</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-bytes%29%29" class="RktValLink" data-pltdoc="x">open-input-bytes</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">#"the cow jumped over the moon\nthe little dog\n"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">"the cow jumped over the moon"</span></p></td></tr></table></blockquote></div></p><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p><span class="imageleft"><img src="magnify.png" alt="+" width="24" height="24"/></span><a href="strings.html" data-pltdoc="x">Strings</a> also provides information on strings.</p></blockquote></blockquote></blockquote><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._open-input-string))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-string%29%29" class="RktValDef RktValLink" data-pltdoc="x">open-input-stri
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encoding (see <a href="encodings.html" data-pltdoc="x">Encodings and Locales</a>) of <span class="RktVar">str</span>. The optional
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<span class="RktVar">name</span> argument is used as the name for the returned port.</div></p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">sp</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-string%29%29" class="RktValLink" data-pltdoc="x">open-input-string</a></span><span class="hspace"> </span><span class="RktVal">"(λ (x) x)"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%29%29" class="RktValLink" data-pltdoc="x">read</a></span><span class="hspace"> </span><span class="RktSym">sp</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">'(λ (x) x)</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">names</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-string%29%29" class="RktValLink" data-pltdoc="x">open-input-string</a></span><span class="hspace"> </span><span class="RktVal">"Günter Harder\nFrédéric Paulin\n"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._read-line%29%29" class="RktValLink" data-pltdoc="x">read-line</a></span><span class="hspace"> </span><span class="RktSym">names</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"Günter Harder"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._read-line%29%29" class="RktValLink" data-pltdoc="x">read-line</a></span><span class="hspace"> </span><span class="RktSym">names</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"Frédéric Paulin"</span></p></td></tr></table></blockquote></div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._open-output-bytes))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-output-bytes%29%29" class="RktValDef RktValLink" data-pltdoc="x">open-output-bytes</a></span></span><span class="hspace"> </span><span class="RktOpt">[</span><span class="RktVar">name</span><span class="RktOpt">]</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._and%2Fc%29%29" class="RktValLink" data-pltdoc="x">and/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="port-ops.html#%28def._%28%28quote._~23~25kernel%29._output-port~3f%29%29" class="RktValLink" data-pltdoc="x">outpu
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byte string. The optional <span class="RktVar">name</span> argument is used as the name for
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the returned port.</div></p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">op1</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-output-bytes%29%29" class="RktValLink" data-pltdoc="x">open-output-bytes</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._write%29%29" class="RktValLink" data-pltdoc="x">write</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">(</span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">2</span><span class="hspace"> </span><span class="RktVal">3</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktVal">(</span><span class="RktVal">"Tom"</span><span class="hspace"> </span><span class="RktVal">"Dick"</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktVal">(</span><span class="RktVal">'</span><span class="RktVal">a</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">b</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">c</span><span class="RktVal">)</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktSym">op1</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span><span class="hspace"> </span><span class="RktSym">op1</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#"((1 2 3) (\"Tom\" \"Dick\") ((quote a) (quote b) (quote c)))"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">op2</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-output-bytes%29%29" class="RktValLink" data-pltdoc="x">open-output-bytes</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._write%29%29" class="RktValLink" data-pltdoc="x">write</a></span><span class="hspace"> </span><span class="RktVal">"Hi "</span><span class="hspace"> </span><span class="RktSym">op2</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._write%29%29" class="RktValLink" data-pltdoc="x">write</a></span><span class="hspace"> </span><span class="RktVal">"there"</span><span class="hspace"> </span><span class="RktSym">op2</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span><span class="hspace"> </span><span class="RktSym">op2</span><span class="RktPn">)</span></td></tr>
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far in a freshly allocated <a href="bytestrings.html#%28tech._byte._string%29" class="techoutside" data-pltdoc="x"><span class="techinside">byte string</span></a> (including any bytes
|
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written after the port’s current position, if any). The <span class="RktVar">out</span>
|
||
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port must be an output <a href="stringport.html#%28tech._string._port%29" class="techoutside" data-pltdoc="x"><span class="techinside">string port</span></a> produced by
|
||
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<span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-output-bytes%29%29" class="RktValLink" data-pltdoc="x">open-output-bytes</a></span> (or <span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-output-string%29%29" class="RktValLink" data-pltdoc="x">open-output-string</a></span>) or a
|
||
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structure whose <span class="RktSym"><a href="portstructs.html#%28def._%28%28quote._~23~25kernel%29._prop~3aoutput-port%29%29" class="RktValLink" data-pltdoc="x">prop:output-port</a></span> property refers to such an
|
||
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output port (transitively).</div></p><p>If <span class="RktVar">reset?</span> is true, then all bytes are removed from the port,
|
||
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and the port’s position is reset to <span class="RktVal">0</span>; if <span class="RktVar">reset?</span> is
|
||
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<span class="RktVal">#f</span>, then all bytes remain in the port for further
|
||
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accumulation (so they are returned for later calls to
|
||
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<span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span> or <span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-string%29%29" class="RktValLink" data-pltdoc="x">get-output-string</a></span>), and the
|
||
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port’s position is unchanged.</p><p>The <span class="RktVar">start-pos</span> and <span class="RktVar">end-pos</span> arguments specify the
|
||
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range of bytes in the port to return; supplying <span class="RktVar">start-pos</span> and
|
||
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<span class="RktVar">end-pos</span> is the same as using <span class="RktSym"><a href="bytestrings.html#%28def._%28%28quote._~23~25kernel%29._subbytes%29%29" class="RktValLink" data-pltdoc="x">subbytes</a></span> on the result
|
||
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of <span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span>, but supplying them to
|
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<span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span> can avoid an allocation. The
|
||
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<span class="RktVar">end-pos</span> argument can be <span class="RktVal">#f</span>, which corresponds to not
|
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passing a second argument to <span class="RktSym"><a href="bytestrings.html#%28def._%28%28quote._~23~25kernel%29._subbytes%29%29" class="RktValLink" data-pltdoc="x">subbytes</a></span>.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">op</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-output-bytes%29%29" class="RktValLink" data-pltdoc="x">open-output-bytes</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._write%29%29" class="RktValLink" data-pltdoc="x">write</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">(</span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">2</span><span class="hspace"> </span><span class="RktVal">3</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktVal">(</span><span class="RktVal">"Tom"</span><span class="hspace"> </span><span class="RktVal">"Dick"</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktVal">(</span><span class="RktVal">'</span><span class="RktVal">a</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">b</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">c</span><span class="RktVal">)</span><span class="RktVal">)</span><span class="hspace"> </span><span class="RktSym">op</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span><span class="hspace"> </span><span class="RktSym">op</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#"((1 2 3) (\"Tom\" \"Dick\") ((quote a) (quote b) (quote c)))"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span><span class="hspace"> </span><span class="RktSym">op</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="hspace"> </span><span class="RktVal">3</span><span class="hspace"> </span><span class="RktVal">16</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#" 2 3) (\"Tom\" "</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span><span class="hspace"> </span><span class="RktSym">op</span><span class="hspace"> </span><span class="RktVal">#t</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#"((1 2 3) (\"Tom\" \"Dick\") ((quote a) (quote b) (quote c)))"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._get-output-bytes%29%29" class="RktValLink" data-pltdoc="x">get-output-bytes</a></span><span class="hspace"> </span><span class="RktSym">op</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#""</span></p></td></tr></table></blockquote></di
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