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href="Tk.html"> <link title="Unix" rel="Chapter" href="Unix.html"> <link title="UnixLabels" rel="Chapter" href="UnixLabels.html"> <link title="Weak" rel="Chapter" href="Weak.html"><title>Printf</title> </head> <body> <div class="navbar"><a class="pre" href="Printexc.html" title="Printexc">Previous</a> <a class="up" href="index.html" title="Index">Up</a> <a class="post" href="Queue.html" title="Queue">Next</a> </div> <h1>Module <a href="type_Printf.html">Printf</a></h1> <pre><span class="keyword">module</span> Printf: <code class="code"><span class="keyword">sig</span></code> <a href="Printf.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><div class="info module top"> Formatted output functions.<br> </div> <hr width="100%"> <pre><span id="VALfprintf"><span class="keyword">val</span> fprintf</span> : <code class="type"><a href="Pervasives.html#TYPEout_channel">out_channel</a> -><br> ('a, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info "> <code class="code">fprintf outchan format arg1 ... argN</code> formats the arguments <code class="code">arg1</code> to <code class="code">argN</code> according to the format string <code class="code">format</code>, and outputs the resulting string on the channel <code class="code">outchan</code>. <p> The format string is a character string which contains two types of objects: plain characters, which are simply copied to the output channel, and conversion specifications, each of which causes conversion and printing of arguments. <p> Conversion specifications have the following form: <p> <code class="code">% [flags] [width] [.precision] <span class="keyword">type</span></code> <p> In short, a conversion specification consists in the <code class="code">%</code> character, followed by optional modifiers and a type which is made of one or two characters. <p> The types and their meanings are: <p> <ul> <li><code class="code">d</code>, <code class="code">i</code>: convert an integer argument to signed decimal.</li> <li><code class="code">u</code>, <code class="code">n</code>, <code class="code">l</code>, <code class="code"><span class="constructor">L</span></code>, or <code class="code"><span class="constructor">N</span></code>: convert an integer argument to unsigned decimal. Warning: <code class="code">n</code>, <code class="code">l</code>, <code class="code"><span class="constructor">L</span></code>, and <code class="code"><span class="constructor">N</span></code> are used for <code class="code">scanf</code>, and should not be used for <code class="code">printf</code>.</li> <li><code class="code">x</code>: convert an integer argument to unsigned hexadecimal, using lowercase letters.</li> <li><code class="code"><span class="constructor">X</span></code>: convert an integer argument to unsigned hexadecimal, using uppercase letters.</li> <li><code class="code">o</code>: convert an integer argument to unsigned octal.</li> <li><code class="code">s</code>: insert a string argument.</li> <li><code class="code"><span class="constructor">S</span></code>: convert a string argument to OCaml syntax (double quotes, escapes).</li> <li><code class="code">c</code>: insert a character argument.</li> <li><code class="code"><span class="constructor">C</span></code>: convert a character argument to OCaml syntax (single quotes, escapes).</li> <li><code class="code">f</code>: convert a floating-point argument to decimal notation, in the style <code class="code">dddd.ddd</code>.</li> <li><code class="code"><span class="constructor">F</span></code>: convert a floating-point argument to OCaml syntax (<code class="code">dddd.</code> or <code class="code">dddd.ddd</code> or <code class="code">d.ddd e+-dd</code>).</li> <li><code class="code">e</code> or <code class="code"><span class="constructor">E</span></code>: convert a floating-point argument to decimal notation, in the style <code class="code">d.ddd e+-dd</code> (mantissa and exponent).</li> <li><code class="code">g</code> or <code class="code"><span class="constructor">G</span></code>: convert a floating-point argument to decimal notation, in style <code class="code">f</code> or <code class="code">e</code>, <code class="code"><span class="constructor">E</span></code> (whichever is more compact).</li> <li><code class="code"><span class="constructor">B</span></code>: convert a boolean argument to the string <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>: convert a boolean argument (deprecated; 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>: convert an <code class="code">int32</code> argument to the format specified by the second letter (decimal, hexadecimal, etc).</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>: convert a <code class="code">nativeint</code> argument to the format specified by the second letter.</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>: convert an <code class="code">int64</code> argument to the format specified by the second letter.</li> <li><code class="code">a</code>: user-defined printer. Take two arguments and apply the first one to <code class="code">outchan</code> (the current output channel) and to the second argument. The first argument must therefore have type <code class="code">out_channel <span class="keywordsign">-></span> <span class="keywordsign">'</span>b <span class="keywordsign">-></span> unit</code> and the second <code class="code"><span class="keywordsign">'</span>b</code>. The output produced by the function is inserted in the output of <code class="code">fprintf</code> at the current point.</li> <li><code class="code">t</code>: same as <code class="code">%a</code>, but take only one argument (with type <code class="code">out_channel <span class="keywordsign">-></span> unit</code>) and apply it to <code class="code">outchan</code>.</li> <li><code class="code">{ fmt %}</code>: convert a format string argument to its type digest. The argument must have the same type as the internal format string <code class="code">fmt</code>.</li> <li><code class="code">( fmt %)</code>: format string substitution. Take a format string argument and substitute it to the internal format string <code class="code">fmt</code> to print following arguments. The argument must have the same type as the internal format string <code class="code">fmt</code>.</li> <li><code class="code">!</code>: take no argument and flush the output.</li> <li><code class="code">%</code>: take no argument and output one <code class="code">%</code> character.</li> <li><code class="code">@</code>: take no argument and output one <code class="code">@</code> character.</li> <li><code class="code">,</code>: take no argument and output nothing: a no-op delimiter for conversion specifications.</li> </ul> The optional <code class="code">flags</code> are:<ul> <li><code class="code">-</code>: left-justify the output (default is right justification).</li> <li><code class="code">0</code>: for numerical conversions, pad with zeroes instead of spaces.</li> <li><code class="code">+</code>: for signed numerical conversions, prefix number with a <code class="code">+</code> sign if positive.</li> <li>space: for signed numerical conversions, prefix number with a space if positive.</li> <li><code class="code"><span class="keywordsign">#</span></code>: request an alternate formatting style for numbers.</li> </ul> The optional <code class="code">width</code> is an integer indicating the minimal width of the result. For instance, <code class="code">%6d</code> prints an integer, prefixing it with spaces to fill at least 6 characters. <p> The optional <code class="code">precision</code> is a dot <code class="code">.</code> followed by an integer indicating how many digits follow the decimal point in the <code class="code">%f</code>, <code class="code">%e</code>, and <code class="code">%<span class="constructor">E</span></code> conversions. For instance, <code class="code">%.4f</code> prints a <code class="code">float</code> with 4 fractional digits. <p> The integer in a <code class="code">width</code> or <code class="code">precision</code> can also be specified as <code class="code">*</code>, in which case an extra integer argument is taken to specify the corresponding <code class="code">width</code> or <code class="code">precision</code>. This integer argument precedes immediately the argument to print. For instance, <code class="code">%.*f</code> prints a <code class="code">float</code> with as many fractional digits as the value of the argument given before the float.<br> </div> <pre><span id="VALprintf"><span class="keyword">val</span> printf</span> : <code class="type">('a, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info "> Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but output on <code class="code">stdout</code>.<br> </div> <pre><span id="VALeprintf"><span class="keyword">val</span> eprintf</span> : <code class="type">('a, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info "> Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but output on <code class="code">stderr</code>.<br> </div> <pre><span id="VALsprintf"><span class="keyword">val</span> sprintf</span> : <code class="type">('a, unit, string) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info "> Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but instead of printing on an output channel, return a string containing the result of formatting the arguments.<br> </div> <pre><span id="VALbprintf"><span class="keyword">val</span> bprintf</span> : <code class="type"><a href="Buffer.html#TYPEt">Buffer.t</a> -> ('a, <a href="Buffer.html#TYPEt">Buffer.t</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info "> Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but instead of printing on an output channel, append the formatted arguments to the given extensible buffer (see module <a href="Buffer.html"><code class="code"><span class="constructor">Buffer</span></code></a>).<br> </div> <pre><span id="VALifprintf"><span class="keyword">val</span> ifprintf</span> : <code class="type">'a -> ('b, 'a, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'b</code></pre><div class="info "> Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but does not print anything. Useful to ignore some material when conditionally printing.<br> <b>Since</b> 3.10.0<br> </div> <br> Formatted output functions with continuations.<br> <pre><span id="VALkfprintf"><span class="keyword">val</span> kfprintf</span> : <code class="type">(<a href="Pervasives.html#TYPEout_channel">out_channel</a> -> 'a) -><br> <a href="Pervasives.html#TYPEout_channel">out_channel</a> -><br> ('b, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info "> Same as <code class="code">fprintf</code>, but instead of returning immediately, passes the out channel to its first argument at the end of printing.<br> <b>Since</b> 3.09.0<br> </div> <pre><span id="VALikfprintf"><span class="keyword">val</span> ikfprintf</span> : <code class="type">(<a href="Pervasives.html#TYPEout_channel">out_channel</a> -> 'a) -><br> <a href="Pervasives.html#TYPEout_channel">out_channel</a> -><br> ('b, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info "> Same as <code class="code">kfprintf</code> above, but does not print anything. Useful to ignore some material when conditionally printing.<br> <b>Since</b> 4.0<br> </div> <pre><span id="VALksprintf"><span class="keyword">val</span> ksprintf</span> : <code class="type">(string -> 'a) -> ('b, unit, string, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info "> Same as <code class="code">sprintf</code> above, but instead of returning the string, passes it to the first argument.<br> <b>Since</b> 3.09.0<br> </div> <pre><span id="VALkbprintf"><span class="keyword">val</span> kbprintf</span> : <code class="type">(<a href="Buffer.html#TYPEt">Buffer.t</a> -> 'a) -><br> <a href="Buffer.html#TYPEt">Buffer.t</a> -> ('b, <a href="Buffer.html#TYPEt">Buffer.t</a>, unit, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info "> Same as <code class="code">bprintf</code>, but instead of returning immediately, passes the buffer to its first argument at the end of printing.<br> <b>Since</b> 3.10.0<br> </div> <br> Deprecated<br> <pre><span id="VALkprintf"><span class="keyword">val</span> kprintf</span> : <code class="type">(string -> 'a) -> ('b, unit, string, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info "> A deprecated synonym for <code class="code">ksprintf</code>.<br> </div> </body></html>