strsep(3)                  Library Functions Manual                  strsep(3)

NAME
       strsep - string separate

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <string.h>

       char *strsep(char **restrict stringp, const char *restrict delim);

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

       strsep():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           glibc 2.19 and earlier:
               _BSD_SOURCE

DESCRIPTION
       If *stringp is NULL, the strsep() function returns NULL and does
       nothing else.  Otherwise, this function finds the first token in the
       string *stringp that is delimited by one of the bytes in the string
       delim.  This token is terminated by overwriting the delimiter with a
       null byte ('\0'), and *stringp is updated to point past the token.  In
       case no delimiter was found, the token is taken to be the entire string
       *stringp, and *stringp is made NULL.

RETURN VALUE
       The strsep() function returns a pointer to the token, that is, it
       returns the original value of *stringp.

ATTRIBUTES
       For an explanation of the terms used in this section, see
       attributes(7).

       +--------------------------------------------+---------------+---------+
       |Interface                                   | Attribute     | Value   |
       +--------------------------------------------+---------------+---------+
       |strsep ()                                   | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       BSD.

HISTORY
       4.4BSD.

       The strsep() function was introduced as a replacement for strtok(3),
       since the latter cannot handle empty fields.

CAVEATS
       Be cautious when using this function.  If you do use it, note that:

       o  The identity of the delimiting character is lost.

EXAMPLES
       The program below is a port of the one found in strtok(3), which,
       however, doesn't discard multiple delimiters or empty tokens:

           $ ./a.out 'a/bbb///cc;xxx:yyy:' ':;' '/'
           1: a/bbb///cc
                    --> a
                    --> bbb
                    -->
                    -->
                    --> cc
           2: xxx
                    --> xxx
           3: yyy
                    --> yyy
           4:
                    -->

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

       int
       main(int argc, char *argv[])
       {
           char *token, *subtoken;

           if (argc != 4) {
               fprintf(stderr, "Usage: %s string delim subdelim\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           for (unsigned int j = 1; (token = strsep(&argv[1], argv[2])); j++) {
               printf("%u: %s\n", j, token);

               while ((subtoken = strsep(&token, argv[3])))
                   printf("\t --> %s\n", subtoken);
           }

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       string(3)

Linux man-pages 6.19              2026-08-10                         strsep(3)