#include <string.h>

       char *strtok(char *str, const char *delim);

       char *strtok_r(char *str, const char *delim, char **saveptr);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       strtok_r(): _SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 1 ||

       The strtok() function parses a string into a sequence  of  tokens.   On
       the  first call to strtok() the string to be parsed should be specified
       in str.  In each subsequent call that should parse the same string, str
       should be NULL.

       The  delim  argument  specifies  a  set  of characters that delimit the
       tokens in the parsed string.  The caller may specify different  strings
       in delim in successive calls that parse the same string.

       Each  call  to  strtok()  returns a pointer to a null-terminated string
       containing the next token.  This string does not include the delimiting
       character.  If no more tokens are found, strtok() returns NULL.

       A sequence of two or more contiguous delimiter characters in the parsed
       string is considered to be a single delimiter.  Delimiter characters at
       the  start  or  end  of  the  string are ignored.  Put another way: the
       tokens returned by strtok() are always nonempty strings.

       The strtok_r() function is a reentrant version strtok().   The  saveptr
       argument  is  a pointer to a char * variable that is used internally by
       strtok_r() in order to maintain context between successive  calls  that
       parse the same string.

       On  the  first call to strtok_r(), str should point to the string to be
       parsed, and the value of saveptr is ignored.  In subsequent calls,  str
       should  be  NULL,  and  saveptr  should be unchanged since the previous

       Different strings may be parsed concurrently using sequences  of  calls
       to strtok_r() that specify different saveptr arguments.

       The  strtok()  and  strtok_r()  functions  return a pointer to the next
       token, or NULL if there are no more tokens.

              SVr4, POSIX.1-2001, 4.3BSD, C89, C99.

         thread safe.  Use strtok_r() if this matters to you.

       The  program  below uses nested loops that employ strtok_r() to break a
       string into a two-level hierarchy of tokens.   The  first  command-line
       argument specifies the string to be parsed.  The second argument speci-
       fies the delimiter character(s) to be used to separate that string into
       "major"  tokens.   The  third  argument specifies the delimiter charac-
       ter(s) to be used to separate the "major" tokens into subtokens.

       An example of the output produced by this program is the following:

           $ ./a.out 'a/bbb///cc;xxx:yyy:' ':;' '/'
           1: a/bbb///cc
                    --> a
                    --> bbb
                    --> cc
           2: xxx
                    --> xxx
           3: yyy
                    --> yyy

   Program source

       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>

       main(int argc, char *argv[])
           char *str1, *str2, *token, *subtoken;
           char *saveptr1, *saveptr2;
           int j;

           if (argc != 4) {
               fprintf(stderr, "Usage: %s string delim subdelim\n",

           for (j = 1, str1 = argv[1]; ; j++, str1 = NULL) {
               token = strtok_r(str1, argv[2], &saveptr1);
               if (token == NULL)
               printf("%d: %s\n", j, token);

               for (str2 = token; ; str2 = NULL) {
                   subtoken = strtok_r(str2, argv[3], &saveptr2);
                   if (subtoken == NULL)
                   printf(" --> %s\n", subtoken);

       This page is part of release 3.35 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at

GNU                               2010-09-27                         STRTOK(3)
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