strsep(3)

NAME
strsep - extract token from string

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
 | Thread safety | MT-Safe

STANDARDS
None.

HISTORY
4.4BSD.

The strsep() function was introduced as a replacement for strtok(3), since the latter cannot handle empty fields. However, strtok(3) conforms to C89/C99 and hence is more portable.

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

•   This function modifies its first argument.

•   This function cannot be used on constant strings.

•   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
memchr(3), strchr(3), string(3), strpbrk(3), strspn(3), strstr(3), strtok(3)