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  47. <a name="strtol"></a>
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  53. <a name="strtol_002c-strtol_005fl_002d_002d_002dstring-to-long"></a>
  54. <h3 class="section">2.38 <code>strtol</code>, <code>strtol_l</code>&mdash;string to long</h3>
  55. <a name="index-strtol"></a>
  56. <a name="index-strtol_005fl"></a>
  57. <a name="index-_005fstrtol_005fr"></a>
  58. <p><strong>Synopsis</strong>
  59. </p><div class="example">
  60. <pre class="example">#include &lt;stdlib.h&gt;
  61. long strtol(const char *restrict <var>s</var>, char **restrict <var>ptr</var>,
  62. int <var>base</var>);
  63. #include &lt;stdlib.h&gt;
  64. long strtol_l(const char *restrict <var>s</var>, char **restrict <var>ptr</var>,
  65. int <var>base</var>, locale_t <var>locale</var>);
  66. long _strtol_r(void *<var>reent</var>, const char *restrict <var>s</var>,
  67. char **restrict <var>ptr</var>,int <var>base</var>);
  68. </pre></div>
  69. <p><strong>Description</strong><br>
  70. The function <code>strtol</code> converts the string <code>*<var>s</var></code> to
  71. a <code>long</code>. First, it breaks down the string into three parts:
  72. leading whitespace, which is ignored; a subject string consisting
  73. of characters resembling an integer in the radix specified by <var>base</var>;
  74. and a trailing portion consisting of zero or more unparseable characters,
  75. and always including the terminating null character. Then, it attempts
  76. to convert the subject string into a <code>long</code> and returns the
  77. result.
  78. </p>
  79. <p>If the value of <var>base</var> is 0, the subject string is expected to look
  80. like a normal C integer constant: an optional sign, a possible &lsquo;<code>0x</code>&rsquo;
  81. indicating a hexadecimal base, and a number. If <var>base</var> is between
  82. 2 and 36, the expected form of the subject is a sequence of letters
  83. and digits representing an integer in the radix specified by <var>base</var>,
  84. with an optional plus or minus sign. The letters <code>a</code>&ndash;<code>z</code> (or,
  85. equivalently, <code>A</code>&ndash;<code>Z</code>) are used to signify values from 10 to 35;
  86. only letters whose ascribed values are less than <var>base</var> are
  87. permitted. If <var>base</var> is 16, a leading <code>0x</code> is permitted.
  88. </p>
  89. <p>The subject sequence is the longest initial sequence of the input
  90. string that has the expected form, starting with the first
  91. non-whitespace character. If the string is empty or consists entirely
  92. of whitespace, or if the first non-whitespace character is not a
  93. permissible letter or digit, the subject string is empty.
  94. </p>
  95. <p>If the subject string is acceptable, and the value of <var>base</var> is zero,
  96. <code>strtol</code> attempts to determine the radix from the input string. A
  97. string with a leading <code>0x</code> is treated as a hexadecimal value; a string with
  98. a leading 0 and no <code>x</code> is treated as octal; all other strings are
  99. treated as decimal. If <var>base</var> is between 2 and 36, it is used as the
  100. conversion radix, as described above. If the subject string begins with
  101. a minus sign, the value is negated. Finally, a pointer to the first
  102. character past the converted subject string is stored in <var>ptr</var>, if
  103. <var>ptr</var> is not <code>NULL</code>.
  104. </p>
  105. <p>If the subject string is empty (or not in acceptable form), no conversion
  106. is performed and the value of <var>s</var> is stored in <var>ptr</var> (if <var>ptr</var> is
  107. not <code>NULL</code>).
  108. </p>
  109. <p><code>strtol_l</code> is like <code>strtol</code> but performs the conversion based on the
  110. locale specified by the locale object locale. If <var>locale</var> is
  111. LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.
  112. </p>
  113. <p>The alternate function <code>_strtol_r</code> is a reentrant version. The
  114. extra argument <var>reent</var> is a pointer to a reentrancy structure.
  115. </p>
  116. <br>
  117. <p><strong>Returns</strong><br>
  118. <code>strtol</code>, <code>strtol_l</code> return the converted value, if any. If no
  119. conversion was made, 0 is returned.
  120. </p>
  121. <p><code>strtol</code>, <code>strtol_l</code> return <code>LONG_MAX</code> or <code>LONG_MIN</code> if the
  122. magnitude of the converted value is too large, and sets <code>errno</code>
  123. to <code>ERANGE</code>.
  124. </p>
  125. <br>
  126. <p><strong>Portability</strong><br>
  127. <code>strtol</code> is ANSI.
  128. <code>strtol_l</code> is a GNU extension.
  129. </p>
  130. <p>No supporting OS subroutines are required.
  131. </p>
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