STRTOK(3) Linux Programmer's Manual STRTOK(3)NAME
strtok, strtok_r - extract tokens from strings
SYNOPSIS
#include <string.h>
char *strtok(char *str, const char *delim);
char *strtok_r(char *str, const char *delim, char **saveptr);
DESCRIPTION
The strtok() function parses a string into a sequence of tokens. On
the first call to strtok() the string to be parsed should be specified
in str. In each subsequent call that should parse the same string, str
should be NULL.
The delim argument specifies a set of characters that delimit the
tokens in the parsed string. The caller may specify different strings
in delim in successive calls that parse the same string.
Each call to strtok() returns a pointer to a null-terminated string
containing the next token. This string does not include the delimiting
character. If no more tokens are found, strtok() returns NULL.
A sequence of two or more contiguous delimiter characters in the parsed
string is considered to be a single delimiter. Delimiter characters at
the start or end of the string are ignored. Put another way: the
tokens returned by strtok() are always non-empty strings.
The strtok_r() function is a reentrant version strtok(). The saveptr
argument is a pointer to a char * variable that is used internally by
strtok_r() in order to maintain context between successive calls that
parse the same string.
On the first call to strtok_r(), str should point to the string to be
parsed, and the value of saveptr is ignored. In subsequent calls, str
should be NULL, and saveptr should be unchanged since the previous
call.
Different strings may be parsed concurrently using sequences of calls
to strtok_r() that specify different saveptr arguments.
EXAMPLE
The following program uses nested loops that employ strtok_r() to break
a string into a two-level hierarchy of tokens. The first command-line
argument specifies the string to be parsed. The second argument speci‐
fies the delimiter character(s) to be used to separate that string into
"major" tokens. The third argument specifies the delimiter charac‐
ter(s) to be used to separate the "major" tokens into subtokens.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(int argc, char *argv[])
{
char *str1, *str2, *token, *subtoken;
char *saveptr1, *saveptr2;
int j;
if (argc != 4) {
fprintf(stderr, "Usage: %s string delim subdelim\n",
argv[0]);
exit(EXIT_FAILURE);
}
for (j = 1, str1 = argv[1]; ; j++, str1 = NULL) {
token = strtok_r(str1, argv[2], &saveptr1);
if (token == NULL)
break;
printf("%d: %s0, j, token);
for (str2 = token; ; str2 = NULL) {
subtoken = strtok_r(str2, argv[3], &saveptr2);
if (subtoken == NULL)
break;
printf(" --> %s0, subtoken);
}
}
exit(EXIT_SUCCESS);
} /* main */
An example of the output produced by this program is the following:
$ ./a.out 'a/bbb///cc;xxx:yyy:' ':;' '/'
1: a/bbb///cc
--> a
--> bbb
--> cc
2: xxx
--> xxx
3: yyy
--> yyy
BUGS
Avoid using these functions. If you do use them, note that:
These functions modify their first argument.
These functions cannot be used on constant strings.
The identity of the delimiting character is lost.
The strtok() function uses a static buffer while parsing, so
it's not thread safe. Use strtok_r() if this matters to you.
RETURN VALUE
The strtok() and strtok_r() functions return a pointer to the next
token, or NULL if there are no more tokens.
CONFORMING TOstrtok()
SVr4, POSIX.1-2001, 4.3BSD, C89.
strtok_r()
POSIX.1-2001
SEE ALSOindex(3), memchr(3), rindex(3), strchr(3), strpbrk(3), strsep(3), str‐
spn(3), strstr(3), wcstok(3)GNU 2000-02-13 STRTOK(3)
