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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
       POSIX.1-2008 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 NUL character,  which  terminates
       the current token. The strtok() function saves a pointer to the follow-
       ing 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 POSIX.1-2008 calls strtok().
       The strtok() function need not 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> charac-
       ters.
           #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);
   Find First two Fields in a Buffer
       The following example uses strtok() to find two  character  strings  (a
       key  and data associated with that key) separated by any combination of
       <space>, <tab>, or <newline> characters at the start of  the  array  of
       characters pointed to by buffer.
           #include <string.h>
           ...
           char    *buffer;
           ...
           struct element {
               char *key;
               char *data;
           } e;
           ...
           // Load the buffer...
           ...
           // Get the key and its data...
           e.key = strtok(buffer, " \t\n");
           e.data = strtok(NULL, " \t\n");
           // Process the rest of the contents of the buffer...
           ...
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 cur-
       rent 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 POSIX.1-2008, <string.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           STRTOK(3P)