Using strtok in c - c

Question

I need to use strtok to read in a first and last name and seperate it. How can I store the names where I can use them idependently in two seperate char arrays?
#include <stdio.h>
#include <string.h>
int main ()
{
char str[] ="test string.";
char * test;
test = strtok (str," ");
while (test != NULL)
{
printf ("%s\n",test);
test= strtok (NULL, " ");
}
return 0;
}

Answer 1

Here is my take at a reasonably simple tokenize helper that
stores results in a dynamically growing array
null-terminating the array
keeps the input string safe (strtok modifies the input string, which is undefined behaviour on a literal char[], at least I think in C99)
To make the code re-entrant, use the non-standard strtok_r
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
char** tokenize(const char* input)
{
char* str = strdup(input);
int count = 0;
int capacity = 10;
char** result = malloc(capacity*sizeof(*result));
char* tok=strtok(str," ");
while(1)
{
if (count >= capacity)
result = realloc(result, (capacity*=2)*sizeof(*result));
result[count++] = tok? strdup(tok) : tok;
if (!tok) break;
tok=strtok(NULL," ");
}
free(str);
return result;
}
int main ()
{
char** tokens = tokenize("test string.");
char** it;
for(it=tokens; it && *it; ++it)
{
printf("%s\n", *it);
free(*it);
}
free(tokens);
return 0;
}
Here is a strtok-free reimplementation of that (uses strpbrk instead):
char** tokenize(const char* str)
{
int count = 0;
int capacity = 10;
char** result = malloc(capacity*sizeof(*result));
const char* e=str;
if (e) do
{
const char* s=e;
e=strpbrk(s," ");
if (count >= capacity)
result = realloc(result, (capacity*=2)*sizeof(*result));
result[count++] = e? strndup(s, e-s) : strdup(s);
} while (e && *(++e));
if (count >= capacity)
result = realloc(result, (capacity+=1)*sizeof(*result));
result[count++] = 0;
return result;
}

Answer 2

Do you need to store them separately? Two pointers into a modified char array will yield two separate perfectly usable strings.
That is we transform this:
char str[] ="test string.";
Into this:
char str[] ="test\0string.";
^ ^
| |
char *s1 ----- |
char *s2 -----------
.
#include <stdio.h>
#include <string.h>
int main ()
{
char str[] ="test string.";
char *firstname = strtok(str, " ");
char *lastname = strtok(NULL, " ");
if (!lastname)
lastname = "";
printf("%s, %s\n", lastname, firstname);
return 0;
}

Answer 3

What about using strcpy:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define MAX_NAMES 2
int main ()
{
char str[] ="test string.";
char *names[MAX_NAMES] = { 0 };
char *test;
int i = 0;
test = strtok (str," ");
while (test != NULL && i < MAX_NAMES)
{
names[i] = malloc(strlen(test)+1);
strcpy(names[i++], test);
test = strtok (NULL, " ");
}
for(i=0; i<MAX_NAMES; ++i)
{
if(names[i])
{
puts(names[i]);
free(names[i]);
names[i] = 0;
}
}
return 0;
}
It contains much clutter to maintain a complete program and clean its resources, but the main point is to use strcpy to copy each token into its own string.

Answer 4

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
char** split(const char *str, const char *delimiter, size_t *len){
char *text, *p, *first, **array;
int c;
char** ret;
*len = 0;
text=strdup(str);
if(text==NULL) return NULL;
for(c=0,p=text;NULL!=(p=strtok(p, delimiter));p=NULL, c++)//count item
if(c==0) first=p; //first token top
ret=(char**)malloc(sizeof(char*)*c+1);//+1 for NULL
if(ret==NULL){
free(text);
return NULL;
}
strcpy(text, str+(first-text));//skip until top token
array=ret;
for(p=text;NULL!=(p=strtok(p, delimiter));p=NULL){
*array++=p;
}
*array=NULL;
*len=c;
return ret;
}
void free4split(char** sa){
char **array=sa;
if(sa!=NULL){
free(array[0]);//for text
free(sa); //for array
}
}
int main(void){
char str[] ="test string.";
char **words;
size_t len=0;
int i;
words = split(str, " \t\r\n,.", &len);
/*
for(char **wk = words; *wk ;wk++){
printf("%s\n", *wk);
}
*/
for(i = 0;i<len;++i){
printf("%s\n", words[i]);
}
free4split(words);
return 0;
}
/* result:
test
string
*/

Answer 5

Copy the results from strtok to a new buffer using a function such as
/*
* Returns a copy of s in freshly allocated memory.
* Exits the process if memory allocation fails.
*/
char *xstrdup(char const *s)
{
char *p = malloc(strlen(s) + 1);
if (p == NULL) {
perror("memory allocation failed");
exit(1);
}
strcpy(p, s);
return p;
}
Don't forget to free the return values when you're done with them.

Answer 6

IMO, you don't need (and probably don't want) to use strtok at all (as in, "for this, or much of anything else"). I think I'd use code something like this:
#include <string.h>
#include <stdlib.h>
static char *make_str(char const *begin, char const *end) {
size_t len = end-begin;
char *ret = malloc(len+1);
if (ret != NULL) {
memcpy(ret, begin, len);
ret[len]='\0';
}
return ret;
}
size_t tokenize(char *tokens[], size_t max, char const *input, char const *delims) {
int i;
char const *start=input, *end=start;
for (i=0; *start && i<max; i++) {
for ( ;NULL!=strchr(delims, *start); ++start)
;
for (end=start; *end && NULL==strchr(delims, *end); ++end)
;
tokens[i] = make_str(start, end);
start = end+1;
}
return i;
}
#ifdef TEST
#define MAX_TOKENS 10
int main() {
char *tokens[MAX_TOKENS];
int i;
size_t num = tokenize(tokens, MAX_TOKENS, "This is a longer input string ", " ");
for (i=0; i<num; i++) {
printf("|%s|\n", tokens[i]);
free(tokens[i]);
}
return 0;
}
#endif

Answer 7

U can do something like this too.
int main ()
{
char str[] ="test string.";
char * temp1;
char * temp2;
temp1 = strtok (str," ");
temp2 = strchr(str, ' ');
if (temp2 != NULL)
temp2++;
printf ("Splitted string :%s, %s\n" , temp1 , temp2);
return
}