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- <a name="strtol"></a>
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- <a name="strtol_002c-strtol_005fl_002d_002d_002dstring-to-long"></a>
- <h3 class="section">2.38 <code>strtol</code>, <code>strtol_l</code>—string to long</h3>
- <a name="index-strtol"></a>
- <a name="index-strtol_005fl"></a>
- <a name="index-_005fstrtol_005fr"></a>
- <p><strong>Synopsis</strong>
- </p><div class="example">
- <pre class="example">#include <stdlib.h>
- long strtol(const char *restrict <var>s</var>, char **restrict <var>ptr</var>,
- int <var>base</var>);
-
- #include <stdlib.h>
- long strtol_l(const char *restrict <var>s</var>, char **restrict <var>ptr</var>,
- int <var>base</var>, locale_t <var>locale</var>);
-
- long _strtol_r(void *<var>reent</var>, const char *restrict <var>s</var>,
- char **restrict <var>ptr</var>,int <var>base</var>);
-
- </pre></div>
- <p><strong>Description</strong><br>
- The function <code>strtol</code> converts the string <code>*<var>s</var></code> to
- a <code>long</code>. First, it breaks down the string into three parts:
- leading whitespace, which is ignored; a subject string consisting
- of characters resembling an integer in the radix specified by <var>base</var>;
- and a trailing portion consisting of zero or more unparseable characters,
- and always including the terminating null character. Then, it attempts
- to convert the subject string into a <code>long</code> and returns the
- result.
- </p>
- <p>If the value of <var>base</var> is 0, the subject string is expected to look
- like a normal C integer constant: an optional sign, a possible ‘<code>0x</code>’
- indicating a hexadecimal base, and a number. If <var>base</var> is between
- 2 and 36, the expected form of the subject is a sequence of letters
- and digits representing an integer in the radix specified by <var>base</var>,
- with an optional plus or minus sign. The letters <code>a</code>–<code>z</code> (or,
- equivalently, <code>A</code>–<code>Z</code>) are used to signify values from 10 to 35;
- only letters whose ascribed values are less than <var>base</var> are
- permitted. If <var>base</var> is 16, a leading <code>0x</code> is permitted.
- </p>
- <p>The subject sequence is the longest initial sequence of the input
- string that has the expected form, starting with the first
- non-whitespace character. If the string is empty or consists entirely
- of whitespace, or if the first non-whitespace character is not a
- permissible letter or digit, the subject string is empty.
- </p>
- <p>If the subject string is acceptable, and the value of <var>base</var> is zero,
- <code>strtol</code> attempts to determine the radix from the input string. A
- string with a leading <code>0x</code> is treated as a hexadecimal value; a string with
- a leading 0 and no <code>x</code> is treated as octal; all other strings are
- treated as decimal. If <var>base</var> is between 2 and 36, it is used as the
- conversion radix, as described above. If the subject string begins with
- a minus sign, the value is negated. Finally, a pointer to the first
- character past the converted subject string is stored in <var>ptr</var>, if
- <var>ptr</var> is not <code>NULL</code>.
- </p>
- <p>If the subject string is empty (or not in acceptable form), no conversion
- is performed and the value of <var>s</var> is stored in <var>ptr</var> (if <var>ptr</var> is
- not <code>NULL</code>).
- </p>
- <p><code>strtol_l</code> is like <code>strtol</code> but performs the conversion based on the
- locale specified by the locale object locale. If <var>locale</var> is
- LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.
- </p>
- <p>The alternate function <code>_strtol_r</code> is a reentrant version. The
- extra argument <var>reent</var> is a pointer to a reentrancy structure.
- </p>
- <br>
- <p><strong>Returns</strong><br>
- <code>strtol</code>, <code>strtol_l</code> return the converted value, if any. If no
- conversion was made, 0 is returned.
- </p>
- <p><code>strtol</code>, <code>strtol_l</code> return <code>LONG_MAX</code> or <code>LONG_MIN</code> if the
- magnitude of the converted value is too large, and sets <code>errno</code>
- to <code>ERANGE</code>.
- </p>
- <br>
- <p><strong>Portability</strong><br>
- <code>strtol</code> is ANSI.
- <code>strtol_l</code> is a GNU extension.
- </p>
- <p>No supporting OS subroutines are required.
- </p>
- <br>
-
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