xref: /freebsd/lib/libc/string/strtok.3 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)

.\" 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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.Dd January 22, 2016
.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.
.Sh RETURN VALUES
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 .
The
.Fn strtok_r
function
conforms to
.St -p1003.1-2001 .
.Sh AUTHORS
.An Wes Peters Aq Mt wes@softweyr.com ,
Softweyr LLC
.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 .