CODEWITHSUNDEEP
cstrtok
Bertholt Stutley Johnson
Bertholt Stutley Johnson

Reputation: 221

Parsing a file with strtok in C

I'm writing a short function to parse through a file by checking string tokens. It should stop when it hits "visgroups", which is the 9th line of the file I am using to test (which is in the buffer called *source). "versioninfo" is the first line. When I run this code it just repeatedly prints out "versioninfo" until I cancel the program manually. Why isn't the strtok function moving on?

I will be doing some different manipulation of the source when I reach this point, that's why the loop control variable is called "active". Would this have anything to do with the fact that strtok isn't thread-safe? I'm not using source in any other threads.

int countVisgroups(int *visgroups, char *source) {
    const char delims[] = {'\t', '\n', ' '};
    int active = 0;
    char *temp;
    while (!active){
        temp = strtok(source, delims);
        if (temp == NULL) {
            printf("%s\n", "Reached end of file while parsing.");   
            return(0);  
        }
        if (strncmp(temp, "visgroups", 9) == 0) {
            active = 1; 
            return(0);  
        }
        printf("%s\n", temp);       
    }
    return(0);
}

Upvotes: 1

Views: 2122

Answers (2)

Ben Jackson
Ben Jackson

Reputation: 93760

Your delims array needs to be nul terminated. Otherwise how can strtok know how many separators you passed in? Normally you'd just use const char *delims = "\t\n " but you could simply add ..., 0 to your initializer.

Upvotes: 3

imreal
imreal

Reputation: 10358

After the first call to strtok with the string you want to tokenize, all subsequent calls must be done with the first parameter set to NULL.

temp = strtok(NULL, delims);

And no it probably doesn't have to do anything with thread safety.

Try to rewrite it like this:

int countVisgroups(int *visgroups, char *source) {
   const char delims[] = {'\t', '\n', ' ', '\0'};
   int active = 0;
   char *temp;
   temp = strtok(source, delims);
   while (!active){
       if (temp == NULL) {
           printf("%s\n", "Reached end of file while parsing.");   
           return(0);  
       }
       if (strncmp(temp, "visgroups", 9) == 0) {
           active = 1; 
           return(0);  
       }
       printf("%s\n", temp);    
       temp = strtok(NULL, delims);   
   }
   return(0);
}

Upvotes: 2

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