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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  corresponding
       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 requirements
       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  con-
       tained  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  vol-
       ume 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 necessary
       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 charac-
       ter 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 sepa-
       rator 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, "    \n");
              data = strtok(NULL, "   \n");
              ...
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 Technology
       --  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)