strtok

[cstudent]

hi again, i have the following code and it has some problem. after doing strtok for the 1st time, when i print out the value of line[0], it returns "hello -a" which is correct. then after the next strtok in the for loop, the result by printing line[0] changes to "hello" i did not do anything to change the value.. so how did it got modified? isit because i did temp = strtok(line[i], ""); and line[i] got changed in the process? please help thanks!

char* string;
string = "hello -a | world -b";
char** line;
char** line2;
char* temp;
int i, count;
i = count = 0;
//do malloc for line and line 2...
......
.....

/*count number of separated commands */
for(i = 0; i < strlen(string); i++) {
    if(strcmp(string[1], "|") ==0){
        sector ++;
    }
}

if(sector) {
   temp = strtok(string, "|");
   while(temp) {
      line[i] = temp;
      i++;
      temp = strtok(NULL, "|");
  }
  printf("&#37;s", line[0]"); //returns hello -a
  for(i = 0; i <= count; i++) {
     temp = strtok(line[i], "");
     line2[i] = temp;
  }
  printf("%s", line[0]");  // returns hello
}

[Elysia]

Strtok damages the input string - it replaced the "token" with 0, so you are only seeing part of the string.
If you don't like the behaviour, you can take a look at my strtok, which is not damaging (the input is always kept intact).

[cstudent]

thanks i will try it out. however, im still interested in knowing how to overcome this problem. am i right to say that when i do temp = strtok(line[i], " "); , something is modified to line?

[Elysia]

OK, say you have a string "Hello World". It's an array of chars as thus: 'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd', '\0'.
When you print it, it detects the end at the '\0'. But when strtok is run with token " ", the char array will then look like:
'H', 'e', 'l', 'l', 'o', '\0', 'W', 'o', 'r', 'l', 'd', '\0'.
(Notice how the space was replaced by '\0'.)
Therefore, functions think the string ends after "Hello" and stops there.
That's why strtok is damaging.
So yes, it modifies the input.

[cstudent]

hahahaha i understand now.. kinda crappy :/ now.. i gotta think of another way to overcome this cos i cant use another your awesome strtok function hopefully most of my brain cells will survive.

[Elysia]

cos i cant use another your awesome strtok function hopefully most of my brain cells will survive.

Any specific reason you can't?
Or do you simply not understand how it works?

[cstudent]

ah i thought of it. maybe if i create a duplicate of line and use strtok on it instead.... maybe it will work. yea theres a reason. i can only have a set of specific files

[Elysia]

Yes, it will work. Not the best way, but sure, it will work.

[cstudent]

heh thanks.

[cstudent]

oh btw, how do u duplicate a copy of char **line with char** lineDup ??

do a loop of line and assign values to lineDup??

[Elysia]

Depends on what char** is. But basically it's just a pointer to pointer, which probably means it's a dynamically allocated 2D array.
Most likely (assuming you have a buffer with enough space), just loop through it using strcpy(dest[x], src[x]).

[whiteflags]

>Most likely (assuming you have a buffer with enough space), just loop through it using strcmp(dest[x][y], src[x][y]).
What?

Malloc enough space for each line* in the new line**
Copy over the data from the old line* to the new line*
And then return the line**

[Elysia]

>Most likely (assuming you have a buffer with enough space), just loop through it using strcmp(dest[x][y], src[x][y]).
What?

Oops, my bad. src[x] and dest[x] it should be along with strcpy.
Ah, this isn't my "C day" it seems

[cstudent]

sigh wat a pain the the ass !

[Elysia]

Then use my strtok. No such pain in the ass.