.\" $OpenBSD: strsep.3,v 1.10 2001/11/21 14:32:45 deraadt Exp $
.\"
.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek.
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.\"	@(#)strsep.3	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt STRSEP 3
.Os
.Sh NAME
.Nm strsep
.Nd separate strings
.Sh SYNOPSIS
.Fd #include <string.h>
.Ft char *
.Fn strsep "char **stringp" "const char *delim"
.Sh DESCRIPTION
The
.Fn strsep
function locates, in the string referenced by
.Fa *stringp ,
the first occurrence of any character in the string
.Fa delim
(or the terminating
.Ql \e0
character) and replaces it with a
.Ql \e0 .
The location of the next character after the delimiter character
(or
.Dv NULL ,
if the end of the string was reached) is stored in
.Fa *stringp .
The original value of
.Fa *stringp
is returned.
.Pp
An
.Dq empty
field, i.e., one caused by two adjacent delimiter characters,
can be detected by comparing the location referenced by the pointer returned
by
.Fn strsep
to
.Ql \e0 .
.Pp
If
.Fa *stringp
is initially
.Dv NULL ,
.Fn strsep
returns
.Dv NULL .
.Sh EXAMPLES
The following uses
.Fn strsep
to parse a string, containing tokens delimited by whitespace, into an
argument vector:
.Bd -literal -offset indent
char **ap, *argv[10], *inputstring;

for (ap = argv; ap < &argv[9] &&
    (*ap = strsep(&inputstring, " \et")) != NULL;) {
	if (**ap != '\e0')
		ap++;
}
*ap = NULL;
.Ed
.Sh HISTORY
The
.Fn strsep
function is intended as a replacement for the
.Fn strtok
function.
While the
.Fn strtok
function should be preferred for portability reasons (it conforms to
.St -ansiC )
it is unable to handle empty fields, i.e., detect fields delimited by
two adjacent delimiter characters, or to be used for more than a single
string at a time.
The
.Fn strsep
function first appeared in
.Bx 4.4 .