1<html lang="en"> 2<head> 3<title>Output Formats - Debugging with GDB</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Debugging with GDB"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Data.html#Data" title="Data"> 9<link rel="prev" href="Arrays.html#Arrays" title="Arrays"> 10<link rel="next" href="Memory.html#Memory" title="Memory"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988-2013 Free Software Foundation, Inc. 14 15Permission is granted to copy, distribute and/or modify this document 16under the terms of the GNU Free Documentation License, Version 1.3 or 17any later version published by the Free Software Foundation; with the 18Invariant Sections being ``Free Software'' and ``Free Software Needs 19Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,'' 20and with the Back-Cover Texts as in (a) below. 21 22(a) The FSF's Back-Cover Text is: ``You are free to copy and modify 23this GNU Manual. 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Sometimes 53this is not what you want. For example, you might want to print a number 54in hex, or a pointer in decimal. Or you might want to view data in memory 55at a certain address as a character string or as an instruction. To do 56these things, specify an <dfn>output format</dfn> when you print a value. 57 58 <p>The simplest use of output formats is to say how to print a value 59already computed. This is done by starting the arguments of the 60<code>print</code> command with a slash and a format letter. The format 61letters supported are: 62 63 <dl> 64<dt><code>x</code><dd>Regard the bits of the value as an integer, and print the integer in 65hexadecimal. 66 67 <br><dt><code>d</code><dd>Print as integer in signed decimal. 68 69 <br><dt><code>u</code><dd>Print as integer in unsigned decimal. 70 71 <br><dt><code>o</code><dd>Print as integer in octal. 72 73 <br><dt><code>t</code><dd>Print as integer in binary. The letter ‘<samp><span class="samp">t</span></samp>’ stands for “two”. 74<a rel="footnote" href="#fn-1" name="fnd-1"><sup>1</sup></a> 75 76 <br><dt><code>a</code><dd><a name="index-unknown-address_002c-locating-571"></a><a name="index-locate-address-572"></a>Print as an address, both absolute in hexadecimal and as an offset from 77the nearest preceding symbol. You can use this format used to discover 78where (in what function) an unknown address is located: 79 80 <pre class="smallexample"> (gdb) p/a 0x54320 81 $3 = 0x54320 <_initialize_vx+396> 82</pre> 83 <p class="noindent">The command <code>info symbol 0x54320</code> yields similar results. 84See <a href="Symbols.html#Symbols">info symbol</a>. 85 86 <br><dt><code>c</code><dd>Regard as an integer and print it as a character constant. This 87prints both the numerical value and its character representation. The 88character representation is replaced with the octal escape ‘<samp><span class="samp">\nnn</span></samp>’ 89for characters outside the 7-bit <span class="sc">ascii</span> range. 90 91 <p>Without this format, <span class="sc">gdb</span> displays <code>char</code>, 92<code>unsigned char</code><!-- /@w -->, and <code>signed char</code><!-- /@w --> data as character 93constants. Single-byte members of vectors are displayed as integer 94data. 95 96 <br><dt><code>f</code><dd>Regard the bits of the value as a floating point number and print 97using typical floating point syntax. 98 99 <br><dt><code>s</code><dd><a name="index-printing-strings-573"></a><a name="index-printing-byte-arrays-574"></a>Regard as a string, if possible. With this format, pointers to single-byte 100data are displayed as null-terminated strings and arrays of single-byte data 101are displayed as fixed-length strings. Other values are displayed in their 102natural types. 103 104 <p>Without this format, <span class="sc">gdb</span> displays pointers to and arrays of 105<code>char</code>, <code>unsigned char</code><!-- /@w -->, and <code>signed char</code><!-- /@w --> as 106strings. Single-byte members of a vector are displayed as an integer 107array. 108 109 <br><dt><code>z</code><dd>Like ‘<samp><span class="samp">x</span></samp>’ formatting, the value is treated as an integer and 110printed as hexadecimal, but leading zeros are printed to pad the value 111to the size of the integer type. 112 113 <br><dt><code>r</code><dd><a name="index-raw-printing-575"></a>Print using the ‘<samp><span class="samp">raw</span></samp>’ formatting. By default, <span class="sc">gdb</span> will 114use a Python-based pretty-printer, if one is available (see <a href="Pretty-Printing.html#Pretty-Printing">Pretty Printing</a>). This typically results in a higher-level display of the 115value's contents. The ‘<samp><span class="samp">r</span></samp>’ format bypasses any Python 116pretty-printer which might exist. 117</dl> 118 119 <p>For example, to print the program counter in hex (see <a href="Registers.html#Registers">Registers</a>), type 120 121<pre class="smallexample"> p/x $pc 122</pre> 123 <p class="noindent">Note that no space is required before the slash; this is because command 124names in <span class="sc">gdb</span> cannot contain a slash. 125 126 <p>To reprint the last value in the value history with a different format, 127you can use the <code>print</code> command with just a format and no 128expression. For example, ‘<samp><span class="samp">p/x</span></samp>’ reprints the last value in hex. 129 130 <div class="footnote"> 131<hr> 132<h4>Footnotes</h4><p class="footnote"><small>[<a name="fn-1" href="#fnd-1">1</a>]</small> ‘<samp><span class="samp">b</span></samp>’ cannot be used because these format letters are also 133used with the <code>x</code> command, where ‘<samp><span class="samp">b</span></samp>’ stands for “byte”; 134see <a href="Memory.html#Memory">Examining Memory</a>.</p> 135 136 <hr></div> 137 138 </body></html> 139 140