separating a string with strtok

Question

I'm looking to separate a line (given as one string) into words. for example: " Hello world". I can have one or more tabs or spaces between the words and in the beginning. I'm trying to do something like this: (findCommand is a function and line is the string I get as input, for this part I only need the first 2 words)

CommandResult findCommand (const char* line){
    char* commandLine = malloc(strlen(line)+1);
    strcpy(commandLine, line);
    char space[] = " \t";
    char* word1 = strtok(commandLine,space);
    char* word2 = strtok(NULL,space);

I've tried to run this in Eclipse with different variations of spaces and tabs. some of them worked fine, on others I get a sigmentation fault and I can't figure out why.

Answer 1

This:

char* commandLine = malloc(sizeof(strlen(line)));

is wrong. You shouldn't use sizeof here, and certainly not on the result of calling strlen(). The above is the same as:

char *commandLine = malloc(sizeof (size_t));

since the return type of strlen() is size_t. Thus, the actual strlen() return value is ignored.

The proper code is:

char *commandLine = malloc(strlen(line) + 1);

since you must add 1 for the terminator, which is not included in the length returned by strlen().

There is no need for any sizeof here, since you're very obviously working with characters.

Answer 2

Use malloc((strlen(line) + 1)* sizeof(char)) instead of malloc(sizeof(strlen(line))). You allocate only space for an integer because sizeof returns an integer.