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  53. <a name="strtok_002c-strtok_005fr_002c-strsep_002d_002d_002dget-next-token-from-a-string"></a>
  54. <h3 class="section">5.42 <code>strtok</code>, <code>strtok_r</code>, <code>strsep</code>&mdash;get next token from a string</h3>
  55. <a name="index-strtok"></a>
  56. <a name="index-strtok_005fr"></a>
  57. <a name="index-strsep"></a>
  58. <p><strong>Synopsis</strong>
  59. </p><div class="example">
  60. <pre class="example">#include &lt;string.h&gt;
  61. char *strtok(char *restrict <var>source</var>,
  62. const char *restrict <var>delimiters</var>);
  63. char *strtok_r(char *restrict <var>source</var>,
  64. const char *restrict <var>delimiters</var>,
  65. char **<var>lasts</var>);
  66. char *strsep(char **<var>source_ptr</var>, const char *<var>delimiters</var>);
  67. </pre></div>
  68. <p><strong>Description</strong><br>
  69. The <code>strtok</code> function is used to isolate sequential tokens in a
  70. null-terminated string, <code>*<var>source</var></code>. These tokens are delimited
  71. in the string by at least one of the characters in <code>*<var>delimiters</var></code>.
  72. The first time that <code>strtok</code> is called, <code>*<var>source</var></code> should be
  73. specified; subsequent calls, wishing to obtain further tokens from
  74. the same string, should pass a null pointer instead. The separator
  75. string, <code>*<var>delimiters</var></code>, must be supplied each time and may
  76. change between calls.
  77. </p>
  78. <p>The <code>strtok</code> function returns a pointer to the beginning of each
  79. subsequent token in the string, after replacing the separator
  80. character itself with a null character. When no more tokens remain,
  81. a null pointer is returned.
  82. </p>
  83. <p>The <code>strtok_r</code> function has the same behavior as <code>strtok</code>, except
  84. a pointer to placeholder <code>*<var>lasts</var></code> must be supplied by the caller.
  85. </p>
  86. <p>The <code>strsep</code> function is similar in behavior to <code>strtok</code>, except
  87. a pointer to the string pointer must be supplied <code><var>source_ptr</var></code> and
  88. the function does not skip leading delimiters. When the string starts
  89. with a delimiter, the delimiter is changed to the null character and
  90. the empty string is returned. Like <code>strtok_r</code> and <code>strtok</code>, the
  91. <code>*<var>source_ptr</var></code> is updated to the next character following the
  92. last delimiter found or NULL if the end of string is reached with
  93. no more delimiters.
  94. </p>
  95. <br>
  96. <p><strong>Returns</strong><br>
  97. <code>strtok</code>, <code>strtok_r</code>, and <code>strsep</code> all return a pointer to the
  98. next token, or <code>NULL</code> if no more tokens can be found. For
  99. <code>strsep</code>, a token may be the empty string.
  100. </p>
  101. <br>
  102. <p><strong>Notes</strong><br>
  103. <code>strtok</code> is unsafe for multi-threaded applications. <code>strtok_r</code>
  104. and <code>strsep</code> are thread-safe and should be used instead.
  105. </p>
  106. <br>
  107. <p><strong>Portability</strong><br>
  108. <code>strtok</code> is ANSI C.
  109. <code>strtok_r</code> is POSIX.
  110. <code>strsep</code> is a BSD extension.
  111. </p>
  112. <p><code>strtok</code>, <code>strtok_r</code>, and <code>strsep</code> require no supporting OS subroutines.
  113. </p>
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