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.Dd $Mdocdate: July 25 2011 $
.Dt STRTOK 3
.Os
.Sh NAME
.Nm strtok ,
.Nm strtok_r
.Nd string token operations
.Sh SYNOPSIS
.Fd #include <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 NUL-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_r
function is a version of
.Fn strtok
that takes an explicit context argument and is reentrant.
.Pp
Since
.Fn strtok
and
.Fn strtok_r
modify the string,
.Fa str
should not point to an area in the initialized data segment.
.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 separator character itself with an
.Tn ASCII NUL
character.
When no more tokens remain, a null pointer is returned.
.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))) {
	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 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 -ansiC .
.Sh HISTORY
The
.Fn strtok
function first appeared in
.At III
and was reimplemented for
.Bx 4.3 Tahoe .
The
.Fn strtok_r
function first appeared in
.Nx 1.3
and was reimplemented for
.Ox 2.7 .
.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 non-null value.
Since this implementation always alters the next starting point,
such a sequence of calls would always return
.Dv NULL .