'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified Sat Jul 24 18:00:10 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified Mon Jan 20 12:04:18 1997 by Andries Brouwer (aeb@cwi.nl)
.\" Modified Tue Jan 23 20:23:07 2001 by Andries Brouwer (aeb@cwi.nl)
.\"
.TH strsep 3 2023-02-05 "Linux man-pages 6.03"
.SH NAME
strsep \- extract token from string
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <string.h>
.PP
.BI "char *strsep(char **restrict " stringp ", const char *restrict " delim );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR strsep ():
.nf
    Since glibc 2.19:
        _DEFAULT_SOURCE
    glibc 2.19 and earlier:
        _BSD_SOURCE
.fi
.SH DESCRIPTION
If
.I *stringp
is NULL, the
.BR strsep ()
function returns NULL
and does nothing else.
Otherwise, this function finds the first token
in the string
.I *stringp
that is delimited by one of the bytes in the string
.IR delim .
This token is terminated by overwriting the delimiter
with a null byte (\[aq]\e0\[aq]),
and
.I *stringp
is updated to point past the token.
In case no delimiter was found, the token is taken to be
the entire string
.IR *stringp ,
and
.I *stringp
is made NULL.
.SH RETURN VALUE
The
.BR strsep ()
function returns a pointer to the token,
that is, it returns the original value of
.IR *stringp .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR strsep ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH STANDARDS
4.4BSD.
.SH NOTES
The
.BR strsep ()
function was introduced as a replacement for
.BR strtok (3),
since the latter cannot handle empty fields.
However,
.BR strtok (3)
conforms to C99 and hence is more portable.
.SH BUGS
Be cautious when using this function.
If you do use it, note that:
.IP \[bu] 3
This function modifies its first argument.
.IP \[bu]
This function cannot be used on constant strings.
.IP \[bu]
The identity of the delimiting character is lost.
.SH EXAMPLES
The program below is a port of the one found in
.BR strtok (3),
which, however, doesn't discard multiple delimiters or empty tokens:
.PP
.in +4n
.EX
.RB "$" " ./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:
         \-\->
.EE
.in
.SS Program source
\&
.\" SRC BEGIN (strsep.c)
.EX
#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\en", argv[0]);
        exit(EXIT_FAILURE);
    }

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

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

    exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR memchr (3),
.BR strchr (3),
.BR string (3),
.BR strpbrk (3),
.BR strspn (3),
.BR strstr (3),
.BR strtok (3)