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 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 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>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 <newline>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 .