What did you initialize the char * to? If something like char *text = “foobar”; then you have a pointer to some read-only characters For char text[7] = “foobar”; then you have a seven element array of characters that you can do what you like with. strtok writes into the string you give it – … Read more
7.21.5.8 the strtok function The standard says the following regarding strtok: [#3] The first call in the sequence searches the string pointed to by s1 for the first character that is not contained in the current separator string pointed to by s2. If no such character is found, then there are no tokens in the … Read more
When strtok() finds a token, it changes the character immediately after the token into a \0, and then returns a pointer to the token. The next time you call it with a NULL argument, it starts looking after the separators that terminated the first token — i.e., after the \0, and possibly further along. Now, … Read more
#include <string.h> char *token; char line[] = “SEVERAL WORDS”; char *search = ” “; // Token will point to “SEVERAL”. token = strtok(line, search); // Token will point to “WORDS”. token = strtok(NULL, search); Update Note that on some operating systems, strtok man page mentions: This interface is obsoleted by strsep(3). An example with strsep … Read more
The documentation for strtok_r is quite clear. 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 … Read more
#include <stdio.h> #include <string.h> int main () { char buf[] =”abc/qwe/ccd”; int i = 0; char *p = strtok (buf, “https://stackoverflow.com/”); char *array[3]; while (p != NULL) { array[i++] = p; p = strtok (NULL, “https://stackoverflow.com/”); } for (i = 0; i < 3; ++i) printf(“%s\n”, array[i]); return 0; }
The problem is that you’re attempting to modify a string literal. Doing so causes your program’s behavior to be undefined. Saying that you’re not allowed to modify a string literal is an oversimplification. Saying that string literals are const is incorrect; they’re not. WARNING : Digression follows. The string literal “this is a test” is … Read more
Yes, strtok(), indeed, uses some static memory to save its context between invocations. Use a reentrant version of strtok(), strtok_r() instead, or strtok_s() if you are using VS (identical to strtok_r()). It has an additional context argument, and you can use different contexts in different loops. char *tok, *saved; for (tok = strtok_r(str, “%”, &saved); … Read more
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 … Read more
strtok() is not reentrant so it should not be used from threaded applications, use strtok_r() instead.