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.\"     from: @(#)strtok.3	8.2 (Berkeley) 2/3/94
.\"	$NetBSD: strtok.3,v 1.21 2004/10/11 14:22:04 dsl Exp $
.\"
.Dd August 11, 2002
.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 * restrict str" "const char * restrict sep"
.Ft char *
.Fn strtok_r "char *str" "const char *sep" "char **lasts"
.Sh DESCRIPTION
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
.Fn strtok
function
returns a pointer to the beginning of each subsequent token in the string,
after replacing the separator character itself with a
.Dv NUL
character.
Separator characters at the beginning of the string or at the
continuation point are skipped so that zero length tokens
are not returned.
When no more tokens remain, a null pointer is returned.
.Pp
The
.Fn strtok_r
function implements the functionality of
.Fn strtok
but is passed an additional argument,
.Fa lasts ,
which points to a user-provided pointer which is used by
.Fn strtok_r
to store state which needs to be kept between calls to scan the same string;
unlike
.Fn strtok ,
it is not necessary to delineate tokenizing to a single string at a time
when using
.Fn strtok_r .
.Sh EXAMPLES
The following will construct an array of pointers to each individual word in
the string
.Va s :
.Bd -literal -offset indent
#define MAXTOKENS	128

char s[512], *p, *tokens[MAXTOKENS];
char *last;
int i = 0;

snprintf(s, sizeof(s), "cat dog horse cow");

for ((p = strtok_r(s, " ", &last)); p;
    (p = strtok_r(NULL, " ", &last)), i++) {
	if (i < MAXTOKENS - 1)
		tokens[i] = p;
}
tokens[i] = NULL;
.Ed
.Pp
That is,
.Li tokens[0]
will point to
.Qq cat ,
.Li tokens[1]
will point to
.Qq dog ,
.Li tokens[2]
will point to
.Qq horse ,
and
.Li tokens[3]
will point to
.Qq cow .
.Sh SEE ALSO
.Xr index 3 ,
.Xr memchr 3 ,
.Xr rindex 3 ,
.Xr strchr 3 ,
.Xr strcspn 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strspn 3 ,
.Xr strstr 3
.Sh STANDARDS
The
.Fn strtok
function
conforms to
.St -ansiC .
The
.Fn strtok_r
function conforms to
.St -p1003.1c-95 .
.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 .