STRTOK(3P)						     POSIX Programmer's Manual							STRTOK(3P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       strtok, strtok_r - split string into tokens

SYNOPSIS

       #include <string.h>

       char *strtok(char *restrict s1, const char *restrict s2);

       char *strtok_r(char *restrict s, const char *restrict sep,
	      char **restrict lasts);

DESCRIPTION

       For strtok():   The functionality described on this reference page is aligned with the ISO C standard. Any conflict  between  the  require-
       ments described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

       A sequence of calls to strtok() breaks the string pointed to by s1 into a sequence of tokens, each of which is delimited by a byte from the
       string pointed to by s2. The first call in the sequence has s1 as its first argument, and is followed by calls with a null pointer as their
       first argument.	The separator string pointed to by s2 may be different from call to call.

       The  first  call  in  the  sequence  searches the string pointed to by s1 for the first byte that is not contained in the current separator
       string pointed to by s2. If no such byte is found, then there are no tokens in the string pointed to by s1 and strtok() shall return a null
       pointer. If such a byte is found, it is the start of the first token.

       The  strtok() function then searches from there for a byte that is contained in the current separator string. If no such byte is found, the
       current token extends to the end of the string pointed to by s1, and subsequent searches for a token shall return a null pointer. If such a
       byte is found, it is overwritten by a null byte, which terminates the current token. The strtok() function saves a pointer to the following
       byte, from which the next search for a token shall start.

       Each subsequent call, with a null pointer as the value of the first argument, starts searching  from  the  saved  pointer  and  behaves	as
       described above.

       The implementation shall behave as if no function defined in this volume of IEEE Std 1003.1-2001 calls strtok().

       The strtok() function need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.

       The  strtok_r() function considers the null-terminated string s as a sequence of zero or more text tokens separated by spans of one or more
       characters from the separator string sep.  The argument lasts points to a user-provided pointer which points to stored  information  neces-
       sary for strtok_r() to continue scanning the same string.

       In  the	first  call  to strtok_r(), s points to a null-terminated string, sep to a null-terminated string of separator characters, and the
       value pointed to by lasts is ignored.  The strtok_r() function shall return a pointer to the first character of the first  token,  write  a
       null character into s immediately following the returned token, and update the pointer to which lasts points.

       In  subsequent  calls,  s is a NULL pointer and lasts shall be unchanged from the previous call so that subsequent calls shall move through
       the string s, returning successive tokens until no tokens remain. The separator string sep may be different from  call  to  call.  When	no
       token remains in s, a NULL pointer shall be returned.

RETURN VALUE

       Upon  successful  completion, strtok() shall return a pointer to the first byte of a token. Otherwise, if there is no token, strtok() shall
       return a null pointer.

       The strtok_r() function shall return a pointer to the token found, or a NULL pointer when no token is found.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

   Searching for Word Separators
       The following example searches for tokens separated by <space>s.

	      #include <string.h>
	      ...
	      char *token;
	      char *line = "LINE TO BE SEPARATED";
	      char *search = " ";

	      /* Token will point to "LINE". */
	      token = strtok(line, search);

	      /* Token will point to "TO". */
	      token = strtok(NULL, search);

   Breaking a Line
       The following example uses strtok() to break a line into two character strings separated by any combination of <space>s, <tab>s,  or  <new-
       line>s.

	      #include <string.h>
	      ...
	      struct element {
		  char *key;
		  char *data;
	      };
	      ...
	      char line[LINE_MAX];
	      char *key, *data;
	      ...
	      key = strtok(line, "    
");
	      data = strtok(NULL, "   
");
	      ...

APPLICATION USAGE

       The strtok_r() function is thread-safe and stores its state in a user-supplied buffer instead of possibly using a static data area that may
       be overwritten by an unrelated call from another thread.

RATIONALE

       The strtok() function searches for a separator string within a larger string. It returns a pointer to the last substring between  separator
       strings.  This function uses static storage to keep track of the current string position between calls. The new function, strtok_r(), takes
       an additional argument, lasts, to keep track of the current position in the string.

FUTURE DIRECTIONS

       None.

SEE ALSO

       The Base Definitions volume of IEEE Std 1003.1-2001, <string.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								STRTOK(3P)