char
*
strtok(
char * restrict str
, const char * restrict sep
)
char
*
strtok_r(
char *str
, const char *sep
, char **lasts
)
)
function
is used to isolate sequential tokens in a nul-terminated string,
str
.
These tokens are separated in the string by at least one of the
characters in
sep
.
The first time that
strtok(
)
is called,
str
should be specified; subsequent calls, wishing to obtain further tokens
from the same string, should pass a null pointer instead.
The separator string,
sep
,
must be supplied each time, and may change between calls.
The
strtok()
function
returns a pointer to the beginning of each subsequent token in the string,
after replacing the separator character itself with a
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.
The
strtok_r()
function implements the functionality of
strtok(
)
but is passed an additional argument,
lasts
,
which points to a user-provided pointer which is used by
strtok_r()
to store state which needs to be kept between calls to scan the same string;
unlike
strtok(
),
it is not necessary to limit tokenizing to a single string at a time
when using
strtok_r(
).
#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;
That is,
tokens[0]
will point to
"cat,
tokens[1]
will point to
"dog,
tokens[2]
will point to
"horse,
and
tokens[3]
will point to
"cow.
)
function
conforms to
ANSI X3.159-1989 (``ANSI C89'') .
The
strtok_r(
)
function conforms to
IEEE Std 1003.1c-1995 (``POSIX.1'') .
),
if handed a string containing only delimiter characters,
will not alter the next starting point, so that a call to
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
NULL
.