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strsep

Section: C Library Functions (3)
Updated: 202-0-08
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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 ([aq][rs]0[aq]), 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	M-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:

[bu]: This function modifies its first argument.
[bu]: This function cannot be used on constant strings.
[bu]: 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 [aq]a/bbb///cc;xxx:yyy:[aq] [aq]:;[aq] [aq]/[aq] 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[rs]n", argv[0]);
        exit(EXIT_FAILURE);
    }
    for (unsigned int j = 1; (token = strsep(&argv[1], argv[2])); j++) {
        printf("%u: %s[rs]n", j, token);
        while ((subtoken = strsep(&token, argv[3])))
            printf("[rs]t --> %s[rs]n", subtoken);
    }
    exit(EXIT_SUCCESS); }

Index

Program source

SEE ALSO