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href="#1_Typeofformattedinputfunctions"> <link title="The general formatted input function" rel="Section" href="#1_Thegeneralformattedinputfunction"> <link title="Format string description" rel="Section" href="#1_Formatstringdescription"> <link title="Specialised formatted input functions" rel="Section" href="#1_Specialisedformattedinputfunctions"> <link title="Reading format strings from input" rel="Section" href="#1_Readingformatstringsfrominput"> <link title="Deprecated" rel="Section" href="#1_Deprecated"> <link title="Functional input with format strings" rel="Subsection" href="#2_Functionalinputwithformatstrings"> <link title="A simple example" rel="Subsection" href="#2_Asimpleexample"> <link title="Formatted input as a functional feature" rel="Subsection" href="#2_Formattedinputasafunctionalfeature"> <link title="The space character in format strings" rel="Subsection" href="#space"> <link title="Conversion specifications in format strings" rel="Subsection" href="#conversion"> <link title="Scanning indications in format strings" rel="Subsection" href="#indication"> <link title="Exceptions during scanning" rel="Subsection" href="#2_Exceptionsduringscanning"> <title>Scanf</title> </head> <body> <div class="navbar"><a class="pre" href="Random.html" title="Random">Previous</a> <a class="up" href="index.html" title="Index">Up</a> <a class="post" href="Seq.html" title="Seq">Next</a> </div> <h1>Module <a href="type_Scanf.html">Scanf</a></h1> <pre><span id="MODULEScanf"><span class="keyword">module</span> Scanf</span>: <code class="code"><span class="keyword">sig</span></code> <a href="Scanf.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><div class="info module top"> <div class="info-desc"> <p>Formatted input functions.</p> </div> </div> <hr width="100%"> <h2 id="1_Introduction">Introduction</h2><h3 id="2_Functionalinputwithformatstrings">Functional input with format strings</h3><p>The module <a href="Scanf.html"><code class="code"><span class="constructor">Scanf</span></code></a> provides formatted input functions or <em>scanners</em>.</p> <p>The formatted input functions can read from any kind of input, including strings, files, or anything that can return characters. The more general source of characters is named a <em>formatted input channel</em> (or <em> scanning buffer</em>) and has type <a href="Scanf.Scanning.html#TYPEin_channel"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.in_channel</code></a>. The more general formatted input function reads from any scanning buffer and is named <code class="code">bscanf</code>.</p> <p>Generally speaking, the formatted input functions have 3 arguments:</p> <ul> <li>the first argument is a source of characters for the input,</li> <li>the second argument is a format string that specifies the values to read,</li> <li>the third argument is a <em>receiver function</em> that is applied to the values read.</li> </ul> <p>Hence, a typical call to the formatted input function <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a> is <code class="code">bscanf ic fmt f</code>, where:</p> <ul> <li><code class="code">ic</code> is a source of characters (typically a <em> formatted input channel</em> with type <a href="Scanf.Scanning.html#TYPEin_channel"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.in_channel</code></a>),</li> </ul> <ul> <li><code class="code">fmt</code> is a format string (the same format strings as those used to print material with module <a href="Printf.html"><code class="code"><span class="constructor">Printf</span></code></a> or <a href="Format.html"><code class="code"><span class="constructor">Format</span></code></a>),</li> </ul> <ul> <li><code class="code">f</code> is a function that has as many arguments as the number of values to read in the input according to <code class="code">fmt</code>.</li> </ul> <h3 id="2_Asimpleexample">A simple example</h3><p>As suggested above, the expression <code class="code">bscanf ic <span class="string">"%d"</span> f</code> reads a decimal integer <code class="code">n</code> from the source of characters <code class="code">ic</code> and returns <code class="code">f n</code>.</p> <p>For instance,</p> <ul> <li>if we use <code class="code">stdin</code> as the source of characters (<a href="Scanf.Scanning.html#VALstdin"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.stdin</code></a> is the predefined formatted input channel that reads from standard input),</li> </ul> <ul> <li>if we define the receiver <code class="code">f</code> as <code class="code"><span class="keyword">let</span> f x = x + 1</code>,</li> </ul> <p>then <code class="code">bscanf <span class="constructor">Scanning</span>.stdin <span class="string">"%d"</span> f</code> reads an integer <code class="code">n</code> from the standard input and returns <code class="code">f n</code> (that is <code class="code">n + 1</code>). Thus, if we evaluate <code class="code">bscanf stdin <span class="string">"%d"</span> f</code>, and then enter <code class="code">41</code> at the keyboard, the result we get is <code class="code">42</code>.</p> <h3 id="2_Formattedinputasafunctionalfeature">Formatted input as a functional feature</h3><p>The OCaml scanning facility is reminiscent of the corresponding C feature. However, it is also largely different, simpler, and yet more powerful: the formatted input functions are higher-order functionals and the parameter passing mechanism is just the regular function application not the variable assignment based mechanism which is typical for formatted input in imperative languages; the OCaml format strings also feature useful additions to easily define complex tokens; as expected within a functional programming language, the formatted input functions also support polymorphism, in particular arbitrary interaction with polymorphic user-defined scanners. Furthermore, the OCaml formatted input facility is fully type-checked at compile time.</p> <h2 id="1_Formattedinputchannel">Formatted input channel</h2> <pre><span id="MODULEScanning"><span class="keyword">module</span> <a href="Scanf.Scanning.html">Scanning</a></span>: <code class="code"><span class="keyword">sig</span></code> <a href="Scanf.Scanning.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><h2 id="1_Typeofformattedinputfunctions">Type of formatted input functions</h2> <pre><span id="TYPEscanner"><span class="keyword">type</span> <code class="type">('a, 'b, 'c, 'd)</code> scanner</span> = <code class="type">('a, <a href="Scanf.Scanning.html#TYPEin_channel">Scanning.in_channel</a>, 'b, 'c, 'a -> 'd, 'd) <a href="Pervasives.html#TYPEformat6">format6</a> -><br> 'c</code> </pre> <div class="info "> <div class="info-desc"> <p>The type of formatted input scanners: <code class="code">(<span class="keywordsign">'</span>a, <span class="keywordsign">'</span>b, <span class="keywordsign">'</span>c, <span class="keywordsign">'</span>d) scanner</code> is the type of a formatted input function that reads from some formatted input channel according to some format string; more precisely, if <code class="code">scan</code> is some formatted input function, then <code class="code">scan<br> ic fmt f</code> applies <code class="code">f</code> to all the arguments specified by format string <code class="code">fmt</code>, when <code class="code">scan</code> has read those arguments from the <a href="Scanf.Scanning.html#TYPEin_channel"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.in_channel</code></a> formatted input channel <code class="code">ic</code>.</p> <p>For instance, the <a href="Scanf.html#VALscanf"><code class="code"><span class="constructor">Scanf</span>.scanf</code></a> function below has type <code class="code">(<span class="keywordsign">'</span>a, <span class="keywordsign">'</span>b, <span class="keywordsign">'</span>c, <span class="keywordsign">'</span>d) scanner</code>, since it is a formatted input function that reads from <a href="Scanf.Scanning.html#VALstdin"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.stdin</code></a>: <code class="code">scanf fmt f</code> applies <code class="code">f</code> to the arguments specified by <code class="code">fmt</code>, reading those arguments from <a href="Pervasives.html#VALstdin"><code class="code">stdin</code></a> as expected.</p> <p>If the format <code class="code">fmt</code> has some <code class="code">%r</code> indications, the corresponding formatted input functions must be provided <em>before</em> receiver function <code class="code">f</code>. For instance, if <code class="code">read_elem</code> is an input function for values of type <code class="code">t</code>, then <code class="code">bscanf ic <span class="string">"%r;"</span> read_elem f</code> reads a value <code class="code">v</code> of type <code class="code">t</code> followed by a <code class="code"><span class="string">';'</span></code> character, and returns <code class="code">f v</code>.</p> </div> <ul class="info-attributes"> <li><b>Since</b> 3.10.0</li> </ul> </div> <pre><span id="EXCEPTIONScan_failure"><span class="keyword">exception</span> Scan_failure</span> <span class="keyword">of</span> <code class="type">string</code></pre> <div class="info "> <div class="info-desc"> <p>When the input can not be read according to the format string specification, formatted input functions typically raise exception <code class="code"><span class="constructor">Scan_failure</span></code>.</p> </div> </div> <h2 id="1_Thegeneralformattedinputfunction">The general formatted input function</h2> <pre><span id="VALbscanf"><span class="keyword">val</span> bscanf</span> : <code class="type"><a href="Scanf.Scanning.html#TYPEin_channel">Scanning.in_channel</a> -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><p><code class="code">bscanf ic fmt r1 ... rN f</code> reads characters from the <a href="Scanf.Scanning.html#TYPEin_channel"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.in_channel</code></a> formatted input channel <code class="code">ic</code> and converts them to values according to format string <code class="code">fmt</code>. As a final step, receiver function <code class="code">f</code> is applied to the values read and gives the result of the <code class="code">bscanf</code> call.</p> <p>For instance, if <code class="code">f</code> is the function <code class="code"><span class="keyword">fun</span> s i <span class="keywordsign">-></span> i + 1</code>, then <code class="code"><span class="constructor">Scanf</span>.sscanf <span class="string">"x= 1"</span> <span class="string">"%s = %i"</span> f</code> returns <code class="code">2</code>.</p> <p>Arguments <code class="code">r1</code> to <code class="code">rN</code> are user-defined input functions that read the argument corresponding to the <code class="code">%r</code> conversions specified in the format string.</p> <h2 id="1_Formatstringdescription">Format string description</h2><p>The format string is a character string which contains three types of objects:</p> <ul> <li>plain characters, which are simply matched with the characters of the input (with a special case for space and line feed, see <a href="Scanf.html#space"><i>The space character in format strings</i></a>),</li> <li>conversion specifications, each of which causes reading and conversion of one argument for the function <code class="code">f</code> (see <a href="Scanf.html#conversion"><i>Conversion specifications in format strings</i></a>),</li> <li>scanning indications to specify boundaries of tokens (see scanning <a href="Scanf.html#indication"><i>Scanning indications in format strings</i></a>).</li> </ul> <h3 id="space">The space character in format strings</h3><p>As mentioned above, a plain character in the format string is just matched with the next character of the input; however, two characters are special exceptions to this rule: the space character (<code class="code"><span class="string">' '</span></code> or ASCII code 32) and the line feed character (<code class="code"><span class="string">'\n'</span></code> or ASCII code 10). A space does not match a single space character, but any amount of 'whitespace' in the input. More precisely, a space inside the format string matches <em>any number</em> of tab, space, line feed and carriage return characters. Similarly, a line feed character in the format string matches either a single line feed or a carriage return followed by a line feed.</p> <p>Matching <em>any</em> amount of whitespace, a space in the format string also matches no amount of whitespace at all; hence, the call <code class="code">bscanf ib<br> <span class="string">"Price = %d $"</span> (<span class="keyword">fun</span> p <span class="keywordsign">-></span> p)</code> succeeds and returns <code class="code">1</code> when reading an input with various whitespace in it, such as <code class="code"><span class="constructor">Price</span> = 1 $</code>, <code class="code"><span class="constructor">Price</span> = 1 $</code>, or even <code class="code"><span class="constructor">Price</span>=1$</code>.</p> <h3 id="conversion">Conversion specifications in format strings</h3><p>Conversion specifications consist in the <code class="code">%</code> character, followed by an optional flag, an optional field width, and followed by one or two conversion characters.</p> <p>The conversion characters and their meanings are:</p> <ul> <li><code class="code">d</code>: reads an optionally signed decimal integer (<code class="code">0-9</code>+).</li> <li><code class="code">i</code>: reads an optionally signed integer (usual input conventions for decimal (<code class="code">0-9</code>+), hexadecimal (<code class="code">0x[0-9a-f]+</code> and <code class="code">0<span class="constructor">X</span>[0-9<span class="constructor">A</span>-<span class="constructor">F</span>]+</code>), octal (<code class="code">0o[0-7]+</code>), and binary (<code class="code">0b[0-1]+</code>) notations are understood).</li> <li><code class="code">u</code>: reads an unsigned decimal integer.</li> <li><code class="code">x</code> or <code class="code"><span class="constructor">X</span></code>: reads an unsigned hexadecimal integer (<code class="code">[0-9a-fA-<span class="constructor">F</span>]+</code>).</li> <li><code class="code">o</code>: reads an unsigned octal integer (<code class="code">[0-7]+</code>).</li> <li><code class="code">s</code>: reads a string argument that spreads as much as possible, until the following bounding condition holds: <ul> <li>a whitespace has been found (see <a href="Scanf.html#space"><i>The space character in format strings</i></a>),</li> <li>a scanning indication (see scanning <a href="Scanf.html#indication"><i>Scanning indications in format strings</i></a>) has been encountered,</li> <li>the end-of-input has been reached.</li> </ul> Hence, this conversion always succeeds: it returns an empty string if the bounding condition holds when the scan begins.</li> <li><code class="code"><span class="constructor">S</span></code>: reads a delimited string argument (delimiters and special escaped characters follow the lexical conventions of OCaml).</li> <li><code class="code">c</code>: reads a single character. To test the current input character without reading it, specify a null field width, i.e. use specification <code class="code">%0c</code>. Raise <code class="code"><span class="constructor">Invalid_argument</span></code>, if the field width specification is greater than 1.</li> <li><code class="code"><span class="constructor">C</span></code>: reads a single delimited character (delimiters and special escaped characters follow the lexical conventions of OCaml).</li> <li><code class="code">f</code>, <code class="code">e</code>, <code class="code"><span class="constructor">E</span></code>, <code class="code">g</code>, <code class="code"><span class="constructor">G</span></code>: reads an optionally signed floating-point number in decimal notation, in the style <code class="code">dddd.ddd<br> e/<span class="constructor">E</span>+-dd</code>.</li> <li><code class="code">h</code>, <code class="code"><span class="constructor">H</span></code>: reads an optionally signed floating-point number in hexadecimal notation.</li> <li><code class="code"><span class="constructor">F</span></code>: reads a floating point number according to the lexical conventions of OCaml (hence the decimal point is mandatory if the exponent part is not mentioned).</li> <li><code class="code"><span class="constructor">B</span></code>: reads a boolean argument (<code class="code"><span class="keyword">true</span></code> or <code class="code"><span class="keyword">false</span></code>).</li> <li><code class="code">b</code>: reads a boolean argument (for backward compatibility; do not use in new programs).</li> <li><code class="code">ld</code>, <code class="code">li</code>, <code class="code">lu</code>, <code class="code">lx</code>, <code class="code">lX</code>, <code class="code">lo</code>: reads an <code class="code">int32</code> argument to the format specified by the second letter for regular integers.</li> <li><code class="code">nd</code>, <code class="code">ni</code>, <code class="code">nu</code>, <code class="code">nx</code>, <code class="code">nX</code>, <code class="code">no</code>: reads a <code class="code">nativeint</code> argument to the format specified by the second letter for regular integers.</li> <li><code class="code"><span class="constructor">Ld</span></code>, <code class="code"><span class="constructor">Li</span></code>, <code class="code"><span class="constructor">Lu</span></code>, <code class="code"><span class="constructor">Lx</span></code>, <code class="code"><span class="constructor">LX</span></code>, <code class="code"><span class="constructor">Lo</span></code>: reads an <code class="code">int64</code> argument to the format specified by the second letter for regular integers.</li> <li><code class="code">[ range ]</code>: reads characters that matches one of the characters mentioned in the range of characters <code class="code">range</code> (or not mentioned in it, if the range starts with <code class="code">^</code>). Reads a <code class="code">string</code> that can be empty, if the next input character does not match the range. The set of characters from <code class="code">c1</code> to <code class="code">c2</code> (inclusively) is denoted by <code class="code">c1-c2</code>. Hence, <code class="code">%[0-9]</code> returns a string representing a decimal number or an empty string if no decimal digit is found; similarly, <code class="code">%[0-9a-f]</code> returns a string of hexadecimal digits. If a closing bracket appears in a range, it must occur as the first character of the range (or just after the <code class="code">^</code> in case of range negation); hence <code class="code">[]]</code> matches a <code class="code">]</code> character and <code class="code">[^]]</code> matches any character that is not <code class="code">]</code>. Use <code class="code">%%</code> and <code class="code">%@</code> to include a <code class="code">%</code> or a <code class="code">@</code> in a range.</li> <li><code class="code">r</code>: user-defined reader. Takes the next <code class="code">ri</code> formatted input function and applies it to the scanning buffer <code class="code">ib</code> to read the next argument. The input function <code class="code">ri</code> must therefore have type <code class="code"><span class="constructor">Scanning</span>.in_channel <span class="keywordsign">-></span> <span class="keywordsign">'</span>a</code> and the argument read has type <code class="code"><span class="keywordsign">'</span>a</code>.</li> <li><code class="code">{ fmt %}</code>: reads a format string argument. The format string read must have the same type as the format string specification <code class="code">fmt</code>. For instance, <code class="code"><span class="string">"%{ %i %}"</span></code> reads any format string that can read a value of type <code class="code">int</code>; hence, if <code class="code">s</code> is the string <code class="code"><span class="string">"fmt:\"number is %u\""</span></code>, then <code class="code"><span class="constructor">Scanf</span>.sscanf s <span class="string">"fmt: %{%i%}"</span></code> succeeds and returns the format string <code class="code"><span class="string">"number is %u"</span></code>.</li> <li><code class="code">( fmt %)</code>: scanning sub-format substitution. Reads a format string <code class="code">rf</code> in the input, then goes on scanning with <code class="code">rf</code> instead of scanning with <code class="code">fmt</code>. The format string <code class="code">rf</code> must have the same type as the format string specification <code class="code">fmt</code> that it replaces. For instance, <code class="code"><span class="string">"%( %i %)"</span></code> reads any format string that can read a value of type <code class="code">int</code>. The conversion returns the format string read <code class="code">rf</code>, and then a value read using <code class="code">rf</code>. Hence, if <code class="code">s</code> is the string <code class="code"><span class="string">"\"%4d\"1234.00"</span></code>, then <code class="code"><span class="constructor">Scanf</span>.sscanf s <span class="string">"%(%i%)"</span> (<span class="keyword">fun</span> fmt i <span class="keywordsign">-></span> fmt, i)</code> evaluates to <code class="code">(<span class="string">"%4d"</span>, 1234)</code>. This behaviour is not mere format substitution, since the conversion returns the format string read as additional argument. If you need pure format substitution, use special flag <code class="code">_</code> to discard the extraneous argument: conversion <code class="code">%_( fmt %)</code> reads a format string <code class="code">rf</code> and then behaves the same as format string <code class="code">rf</code>. Hence, if <code class="code">s</code> is the string <code class="code"><span class="string">"\"%4d\"1234.00"</span></code>, then <code class="code"><span class="constructor">Scanf</span>.sscanf s <span class="string">"%_(%i%)"</span></code> is simply equivalent to <code class="code"><span class="constructor">Scanf</span>.sscanf <span class="string">"1234.00"</span> <span class="string">"%4d"</span></code>.</li> <li><code class="code">l</code>: returns the number of lines read so far.</li> <li><code class="code">n</code>: returns the number of characters read so far.</li> <li><code class="code"><span class="constructor">N</span></code> or <code class="code"><span class="constructor">L</span></code>: returns the number of tokens read so far.</li> <li><code class="code">!</code>: matches the end of input condition.</li> <li><code class="code">%</code>: matches one <code class="code">%</code> character in the input.</li> <li><code class="code">@</code>: matches one <code class="code">@</code> character in the input.</li> <li><code class="code">,</code>: does nothing.</li> </ul> <p>Following the <code class="code">%</code> character that introduces a conversion, there may be the special flag <code class="code">_</code>: the conversion that follows occurs as usual, but the resulting value is discarded. For instance, if <code class="code">f</code> is the function <code class="code"><span class="keyword">fun</span> i <span class="keywordsign">-></span> i + 1</code>, and <code class="code">s</code> is the string <code class="code"><span class="string">"x = 1"</span></code>, then <code class="code"><span class="constructor">Scanf</span>.sscanf s <span class="string">"%_s = %i"</span> f</code> returns <code class="code">2</code>.</p> <p>The field width is composed of an optional integer literal indicating the maximal width of the token to read. For instance, <code class="code">%6d</code> reads an integer, having at most 6 decimal digits; <code class="code">%4f</code> reads a float with at most 4 characters; and <code class="code">%8[\000-\255]</code> returns the next 8 characters (or all the characters still available, if fewer than 8 characters are available in the input).</p> <p>Notes:</p> <ul> <li>as mentioned above, a <code class="code">%s</code> conversion always succeeds, even if there is nothing to read in the input: in this case, it simply returns <code class="code"><span class="string">""</span></code>.</li> </ul> <ul> <li>in addition to the relevant digits, <code class="code"><span class="string">'_'</span></code> characters may appear inside numbers (this is reminiscent to the usual OCaml lexical conventions). If stricter scanning is desired, use the range conversion facility instead of the number conversions.</li> </ul> <ul> <li>the <code class="code">scanf</code> facility is not intended for heavy duty lexical analysis and parsing. If it appears not expressive enough for your needs, several alternative exists: regular expressions (module <a href="Str.html"><code class="code"><span class="constructor">Str</span></code></a>), stream parsers, <code class="code">ocamllex</code>-generated lexers, <code class="code">ocamlyacc</code>-generated parsers.</li> </ul> <h3 id="indication">Scanning indications in format strings</h3><p>Scanning indications appear just after the string conversions <code class="code">%s</code> and <code class="code">%[ range ]</code> to delimit the end of the token. A scanning indication is introduced by a <code class="code">@</code> character, followed by some plain character <code class="code">c</code>. It means that the string token should end just before the next matching <code class="code">c</code> (which is skipped). If no <code class="code">c</code> character is encountered, the string token spreads as much as possible. For instance, <code class="code"><span class="string">"%s@\t"</span></code> reads a string up to the next tab character or to the end of input. If a <code class="code">@</code> character appears anywhere else in the format string, it is treated as a plain character.</p> <p>Note:</p> <ul> <li>As usual in format strings, <code class="code">%</code> and <code class="code">@</code> characters must be escaped using <code class="code">%%</code> and <code class="code">%@</code>; this rule still holds within range specifications and scanning indications. For instance, format <code class="code"><span class="string">"%s@%%"</span></code> reads a string up to the next <code class="code">%</code> character, and format <code class="code"><span class="string">"%s@%@"</span></code> reads a string up to the next <code class="code">@</code>.</li> <li>The scanning indications introduce slight differences in the syntax of <a href="Scanf.html"><code class="code"><span class="constructor">Scanf</span></code></a> format strings, compared to those used for the <a href="Printf.html"><code class="code"><span class="constructor">Printf</span></code></a> module. However, the scanning indications are similar to those used in the <a href="Format.html"><code class="code"><span class="constructor">Format</span></code></a> module; hence, when producing formatted text to be scanned by <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, it is wise to use printing functions from the <a href="Format.html"><code class="code"><span class="constructor">Format</span></code></a> module (or, if you need to use functions from <a href="Printf.html"><code class="code"><span class="constructor">Printf</span></code></a>, banish or carefully double check the format strings that contain <code class="code"><span class="string">'@'</span></code> characters).</li> </ul> <h3 id="2_Exceptionsduringscanning">Exceptions during scanning</h3><p>Scanners may raise the following exceptions when the input cannot be read according to the format string:</p> <ul> <li>Raise <a href="Scanf.html#EXCEPTIONScan_failure"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scan_failure</span></code></a> if the input does not match the format.</li> </ul> <ul> <li>Raise <code class="code"><span class="constructor">Failure</span></code> if a conversion to a number is not possible.</li> </ul> <ul> <li>Raise <code class="code"><span class="constructor">End_of_file</span></code> if the end of input is encountered while some more characters are needed to read the current conversion specification.</li> </ul> <ul> <li>Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the format string is invalid.</li> </ul> <p>Note:</p> <ul> <li>as a consequence, scanning a <code class="code">%s</code> conversion never raises exception <code class="code"><span class="constructor">End_of_file</span></code>: if the end of input is reached the conversion succeeds and simply returns the characters read so far, or <code class="code"><span class="string">""</span></code> if none were ever read.</li> </ul> <h2 id="1_Specialisedformattedinputfunctions">Specialised formatted input functions</h2> <pre><span id="VALsscanf"><span class="keyword">val</span> sscanf</span> : <code class="type">string -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info "> <div class="info-desc"> <p>Same as <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, but reads from the given string.</p> </div> </div> <pre><span id="VALscanf"><span class="keyword">val</span> scanf</span> : <code class="type">('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info "> <div class="info-desc"> <p>Same as <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, but reads from the predefined formatted input channel <a href="Scanf.Scanning.html#VALstdin"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.stdin</code></a> that is connected to <a href="Pervasives.html#VALstdin"><code class="code">stdin</code></a>.</p> </div> </div> <pre><span id="VALkscanf"><span class="keyword">val</span> kscanf</span> : <code class="type"><a href="Scanf.Scanning.html#TYPEin_channel">Scanning.in_channel</a> -><br> (<a href="Scanf.Scanning.html#TYPEin_channel">Scanning.in_channel</a> -> exn -> 'd) -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info "> <div class="info-desc"> <p>Same as <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, but takes an additional function argument <code class="code">ef</code> that is called in case of error: if the scanning process or some conversion fails, the scanning function aborts and calls the error handling function <code class="code">ef</code> with the formatted input channel and the exception that aborted the scanning process as arguments.</p> </div> </div> <pre><span id="VALksscanf"><span class="keyword">val</span> ksscanf</span> : <code class="type">string -><br> (<a href="Scanf.Scanning.html#TYPEin_channel">Scanning.in_channel</a> -> exn -> 'd) -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info "> <div class="info-desc"> <p>Same as <a href="Scanf.html#VALkscanf"><code class="code"><span class="constructor">Scanf</span>.kscanf</code></a> but reads from the given string.</p> </div> <ul class="info-attributes"> <li><b>Since</b> 4.02.0</li> </ul> </div> <h2 id="1_Readingformatstringsfrominput">Reading format strings from input</h2> <pre><span id="VALbscanf_format"><span class="keyword">val</span> bscanf_format</span> : <code class="type"><a href="Scanf.Scanning.html#TYPEin_channel">Scanning.in_channel</a> -><br> ('a, 'b, 'c, 'd, 'e, 'f) <a href="Pervasives.html#TYPEformat6">format6</a> -><br> (('a, 'b, 'c, 'd, 'e, 'f) <a href="Pervasives.html#TYPEformat6">format6</a> -> 'g) -> 'g</code></pre><div class="info "> <div class="info-desc"> <p><code class="code">bscanf_format ic fmt f</code> reads a format string token from the formatted input channel <code class="code">ic</code>, according to the given format string <code class="code">fmt</code>, and applies <code class="code">f</code> to the resulting format string value. Raise <a href="Scanf.html#EXCEPTIONScan_failure"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scan_failure</span></code></a> if the format string value read does not have the same type as <code class="code">fmt</code>.</p> </div> <ul class="info-attributes"> <li><b>Since</b> 3.09.0</li> </ul> </div> <pre><span id="VALsscanf_format"><span class="keyword">val</span> sscanf_format</span> : <code class="type">string -><br> ('a, 'b, 'c, 'd, 'e, 'f) <a href="Pervasives.html#TYPEformat6">format6</a> -><br> (('a, 'b, 'c, 'd, 'e, 'f) <a href="Pervasives.html#TYPEformat6">format6</a> -> 'g) -> 'g</code></pre><div class="info "> <div class="info-desc"> <p>Same as <a href="Scanf.html#VALbscanf_format"><code class="code"><span class="constructor">Scanf</span>.bscanf_format</code></a>, but reads from the given string.</p> </div> <ul class="info-attributes"> <li><b>Since</b> 3.09.0</li> </ul> </div> <pre><span id="VALformat_from_string"><span class="keyword">val</span> format_from_string</span> : <code class="type">string -><br> ('a, 'b, 'c, 'd, 'e, 'f) <a href="Pervasives.html#TYPEformat6">format6</a> -><br> ('a, 'b, 'c, 'd, 'e, 'f) <a href="Pervasives.html#TYPEformat6">format6</a></code></pre><div class="info "> <div class="info-desc"> <p><code class="code">format_from_string s fmt</code> converts a string argument to a format string, according to the given format string <code class="code">fmt</code>. Raise <a href="Scanf.html#EXCEPTIONScan_failure"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scan_failure</span></code></a> if <code class="code">s</code>, considered as a format string, does not have the same type as <code class="code">fmt</code>.</p> </div> <ul class="info-attributes"> <li><b>Since</b> 3.10.0</li> </ul> </div> <pre><span id="VALunescaped"><span class="keyword">val</span> unescaped</span> : <code class="type">string -> string</code></pre><div class="info "> <div class="info-desc"> <p><code class="code">unescaped s</code> return a copy of <code class="code">s</code> with escape sequences (according to the lexical conventions of OCaml) replaced by their corresponding special characters. More precisely, <code class="code"><span class="constructor">Scanf</span>.unescaped</code> has the following property: for all string <code class="code">s</code>, <code class="code"><span class="constructor">Scanf</span>.unescaped (<span class="constructor">String</span>.escaped s) = s</code>.</p> <p>Always return a copy of the argument, even if there is no escape sequence in the argument. Raise <a href="Scanf.html#EXCEPTIONScan_failure"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scan_failure</span></code></a> if <code class="code">s</code> is not properly escaped (i.e. <code class="code">s</code> has invalid escape sequences or special characters that are not properly escaped). For instance, <code class="code"><span class="constructor">String</span>.unescaped <span class="string">"\""</span></code> will fail.</p> </div> <ul class="info-attributes"> <li><b>Since</b> 4.00.0</li> </ul> </div> <h2 id="1_Deprecated">Deprecated</h2> <pre><span id="VALfscanf"><span class="keyword">val</span> fscanf</span> : <code class="type"><a href="Pervasives.html#TYPEin_channel">in_channel</a> -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info "> <div class="info-deprecated"> <span class="warning">Deprecated.</span><code class="code"><span class="constructor">Scanf</span>.fscanf</code> is error prone and deprecated since 4.03.0. This function violates the following invariant of the <a href="Scanf.html"><code class="code"><span class="constructor">Scanf</span></code></a> module: To preserve scanning semantics, all scanning functions defined in <a href="Scanf.html"><code class="code"><span class="constructor">Scanf</span></code></a> must read from a user defined <a href="Scanf.Scanning.html#TYPEin_channel"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.in_channel</code></a> formatted input channel. If you need to read from a <a href="Pervasives.html#TYPEin_channel"><code class="code">in_channel</code></a> input channel <code class="code">ic</code>, simply define a <a href="Scanf.Scanning.html#TYPEin_channel"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.in_channel</code></a> formatted input channel as in <code class="code"><span class="keyword">let</span> ib = <span class="constructor">Scanning</span>.from_channel ic</code>, then use <code class="code"><span class="constructor">Scanf</span>.bscanf ib</code> as usual.</div> </div> <pre><span id="VALkfscanf"><span class="keyword">val</span> kfscanf</span> : <code class="type"><a href="Pervasives.html#TYPEin_channel">in_channel</a> -><br> (<a href="Scanf.Scanning.html#TYPEin_channel">Scanning.in_channel</a> -> exn -> 'd) -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info "> <div class="info-deprecated"> <span class="warning">Deprecated.</span><code class="code"><span class="constructor">Scanf</span>.kfscanf</code> is error prone and deprecated since 4.03.0.</div> </div> </body></html>