NULL in second call of strtok()

[gauravgaharwar]

I hve to use NULL as the first arguement in strtok() after first call, i want to know that why i have to use NULL as arguement in place of actual string?

[sicarie]

I hve to use NULL as the first arguement in strtok() after first call, i want to know that why i have to use NULL as arguement in place of actual string?

Well, if you look at the strtok() documentation the first argument is the string you want to be parsed. If you are not passing it a string, you can't parse null for anything but null, and why are you even using strtok() to do nothing?

[Studlyami]

The first call you use a char array which has the elements you want parsed.
The second time you call it you pass it NULL as the first parameter to tell function to resume from the last spot in the string. Once the first call is made your char array receives the parsed string. If you don't put NULL you would lose your place and effectivly the last part of your string.
char * c_Ptr = NULL; //temp hold indivisual sections
char c_Ptr1[1000] = {NULL};
fgets(c_Ptr1, 1000, f_ptr) //Grabs a line from an open file

strtok(c_Ptr1, ","); //first one starts at the beginning

c_Ptr = strtok(NULL, ",");

[sicarie]

The first call you use a char array which has the elements you want parsed.
The second time you call it you pass it NULL as the first parameter to tell function to resume from the last spot in the string. Once the first call is made your char array receives the parsed string. If you don't put NULL you would lose your place and effectivly the last part of your string.
char * c_Ptr = NULL; //temp hold indivisual sections
char c_Ptr1[1000] = {NULL};
fgets(c_Ptr1, 1000, f_ptr) //Grabs a line from an open file

strtok(c_Ptr1, ","); //first one starts at the beginning

c_Ptr = strtok(NULL, ",");

Ah, after the first call. Good catch, Studlyami.

[weaknessforcats]

Yes, good ol'strtok(). It keeps its position in a static variable. So if you use this thing in a multithreaded program you are on the road to a crash.

strtok() is OK for trivial programs or single-threaded programs. However, for real modern softweare programs, write a parser that doesn't use static variables.

[Studlyami]

What type of functions parse without using static variables? I've always used strtok to parse a file.

[weaknessforcats]

What type of functions parse without using static variables? I've always used strtok to parse a file.

You use a design pattern called State. There is an article on this in the C/C++ Articles forum. The examples are C++ but anything written in C++ can be written in C. It just takes a ton more work.