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 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 NUL character, 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 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 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> characters.

           #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 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 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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2013                                        STRTOK(3POSIX)