xref: /freebsd/lib/libc/string/strtok.3 (revision 24a0682c6465290759ed0b09ea16e40e7cd47053)

.\" Copyright (c) 1998 Softweyr LLC.  All rights reserved.
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.\" strtok_r, from Berkeley strtok
.\" Oct 13, 1998 by Wes Peters <wes@softweyr.com>
.\"
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.\" the American National Standards Committee X3, on Information
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.\"     @(#)strtok.3	8.2 (Berkeley) 2/3/94
.\" $FreeBSD$
.\"
.Dd November 27, 1998
.Dt STRTOK 3
.Os
.Sh NAME
.Nm strtok , strtok_r
.Nd string tokens
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn strtok "char *str" "const char *sep"
.Ft char *
.Fn strtok_r "char *str" "const char *sep" "char **last"
.Sh DESCRIPTION
.Bf -symbolic
This interface is obsoleted by
.Xr strsep 3 .
.Ef
.Pp
The
.Fn strtok
function
is used to isolate sequential tokens in a null-terminated string,
.Fa str .
These tokens are separated in the string by at least one of the
characters in
.Fa sep .
The first time that
.Fn strtok
is called,
.Fa str
should be specified; subsequent calls, wishing to obtain further tokens
from the same string, should pass a null pointer instead.
The separator string,
.Fa sep ,
must be supplied each time, and may change between calls.
.Pp
The implementation will behave as if no library function calls
.Fn strtok .
.Pp
The
.Fn strtok_r
function is a reentrant version of
.Fn strtok .
The context pointer
.Fa last
must be provided on each call.
The
.Fn strtok_r
function
may also be used to nest two parsing loops within one another, as
long as separate context pointers are used.
.Pp
The
.Fn strtok
and
.Fn strtok_r
functions
return a pointer to the beginning of each subsequent token in the string,
after replacing the token itself with a
.Dv NUL
character.
When no more tokens remain, a null pointer is returned.
.Sh EXAMPLES
The following uses
.Fn strtok_r
to parse two strings using separate contexts:
.Bd -literal
char test[80], blah[80];
char *sep = "\e\e/:;=-";
char *word, *phrase, *brkt, *brkb;

strcpy(test, "This;is.a:test:of=the/string\e\etokenizer-function.");

for (word = strtok_r(test, sep, &brkt);
     word;
     word = strtok_r(NULL, sep, &brkt))
{
    strcpy(blah, "blah:blat:blab:blag");

    for (phrase = strtok_r(blah, sep, &brkb);
         phrase;
         phrase = strtok_r(NULL, sep, &brkb))
    {
        printf("So far we're at %s:%s\en", word, phrase);
    }
}
.Ed
.Sh SEE ALSO
.Xr memchr 3 ,
.Xr strchr 3 ,
.Xr strcspn 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strspn 3 ,
.Xr strstr 3 ,
.Xr wcstok 3
.Sh STANDARDS
The
.Fn strtok
function
conforms to
.St -isoC .
.Sh AUTHORS
.An Wes Peters ,
Softweyr LLC:
.Aq wes@softweyr.com
.Pp
Based on the
.Fx 3.0
implementation.
.Sh BUGS
The System V
.Fn strtok ,
if handed a string containing only delimiter characters,
will not alter the next starting point, so that a call to
.Fn strtok
with a different (or empty) delimiter string
may return a
.Pf non- Dv NULL
value.
Since this implementation always alters the next starting point,
such a sequence of calls would always return
.Dv NULL .