man3/strtok.3

   1 .\" Copyright (C) 1996 Andries Brouwer (aeb@cwi.nl)
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  23 .\" Rewritten old page, 960210, aeb@cwi.nl
  24 .\" Updated, added strtok_r. 2000-02-13 Nicolás Lichtmaier <nick@debian.org>
  25 .TH STRTOK 3  2000-02-13 "GNU" "Linux Programmer's Manual"
  26 .SH NAME
  27 strtok, strtok_r \- extract tokens from strings
  28 .SH SYNOPSIS
  29 .nf
  30 .B #include <string.h>
  31 .sp
  32 .BI "char *strtok(char *" s ", const char *" delim );
  33 .sp
  34 .BI "char *strtok_r(char *" s ", const char *" delim ", char **" ptrptr );
  35 .fi
  36 .SH DESCRIPTION
  37 A `token' is a nonempty string of characters not occurring in
  38 the string \fIdelim\fP, followed by \e0 or by a character occurring
  39 in \fIdelim\fP.
  40 .PP
  41 The \fBstrtok\fP() function can be used to parse the string \fIs\fP
  42 into tokens. The first call to \fBstrtok\fP() should have \fIs\fP
  43 as its first argument. Subsequent calls should have the first argument
  44 set to NULL. Each call returns a pointer to the next token, or NULL
  45 when no more tokens are found.
  46 .PP
  47 If a token ends with a delimiter, this delimiting character is
  48 overwritten with a \e0 and a pointer to the next character is
  49 saved for the next call to \fBstrtok\fP().
  50 The delimiter string \fIdelim\fP may be different for each call.
  51 .PP
  52 The
  53 .BR strtok_r ()
  54 function is a reentrant version of the
  55 .BR strtok ()
  56 function, which instead of using its own static buffer, requires a pointer
  57 to a user allocated char*. This pointer, the
  58 .I ptrptr
  59 parameter, must be the same while parsing the same string.
  60 .\" .SH EXAMPLE
  61 .\" The following parses words out of a string, using 'white space'
  62 .\" separators, with
  63 .\" .BR strtok_r() :
  64 .\" .PP
  65 .\" .nf
  66 .\" char buf[128];
  67 .\" char *sep = " \\t\\n";
  68 .\" char *tok, *cb;
  69 .\"
  70 .\"     snprintf(buf, sizeof(buf), "%s", "   One Two\\tThree\\nFour\\n\\n");
  71 .\"
  72 .\"     for ( tok = strtok_r(buf, sep, &cb); tok;
  73 .\"           tok = strtok_r(NULL, sep, &cb) )
  74 .\"             printf("%s\\n", tok);
  75 .\" .fi
  76 .SH BUGS
  77 Never use these functions. If you do, note that:
  78 .PP
  79 .RS
  80 These functions modify their first argument.
  81 .PP
  82 These functions cannot be used on constant strings.
  83 .PP
  84 The identity of the delimiting character is lost.
  85 .PP
  86 The
  87 .BR strtok ()
  88 function uses a static buffer while parsing, so it's not thread safe. Use
  89 .BR strtok_r ()
  90 if this matters to you.
  91 .RE
  92 .SH "RETURN VALUE"
  93 The \fBstrtok\fP() function returns a pointer to the next token, or
  94 NULL if there are no more tokens.
  95 .SH "CONFORMING TO"
  96 .TP
  97 strtok()
  98 SVID 3, POSIX, 4.3BSD, ISO 9899
  99 .TP
 100 strtok_r()
 101 POSIX.1c
 102 .SH "SEE ALSO"
 103 .BR index (3),
 104 .BR memchr (3),
 105 .BR rindex (3),
 106 .BR strchr (3),
 107 .BR strpbrk (3),
 108 .BR strsep (3),
 109 .BR strspn (3),
 110 .BR strstr (3)