Using strtok() in nested loops in C?

c string strtok
Alex Xander picture Alex Xander · Oct 2, 2009 · Viewed 12k times · Source

I am trying to use strtok() in nested loops but this is not giving me desired results, possibly because they are using the same memory location. My code is of the form:-

char *token1 = strtok(Str1, "%");
while (token1 != NULL)
{
    char *token2 = strtok(Str2, "%");
    while (token2 != NULL)
    {
        //Do something
        token2 = strtok(NULL, "%");
    }
    // Do something more
    token1 = strtok(NULL, "%");
}

Answer

Alex B picture Alex B · Oct 2, 2009

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); tok; tok = strtok_r(NULL, "%", &saved))
{
    /* Do something with "tok" */
}

Related questions

How does strtok() split the string into tokens in C?

Please explain to me the working of strtok() function. The manual says it breaks the string into tokens. I am unable to understand from the manual what it actually does. I added watches on str and *pch to check its …

Read More
How to split a string to 2 strings in C

I was wondering how you could take 1 string, split it into 2 with a delimiter, such as space, and assign the 2 parts to 2 separate strings. I've tried using strtok() but to no avail.

Read More
Converting Char * to Uppercase in C

I'm trying to convert a char * to uppercase in c, but the function toupper() doesn't work here. I'm trying to get the name of the the value of temp, the name being anything before the colon, in this case it's "…

Read More