Question

I was hoping someone could help me figure out why I am getting a segmentation fault on my code below. My user has inputted a line of text, which is passed to the parse function. The parse function should initialize a 2D array (I would ideally like to dynamically allocate the array, but for now I am making it an array of size [25][25]).

Starting at the beginning of input strtok() is called. If strtok() sees a pipe symbol, it should increase the count of pipes and go to the next row of the matrix. For example, if the user inputted foo bar | foo1 | foo2 bar1 foo2, the 2D array would look like:

array[][] = { foo, barr;
              foo1;
              foo2, bar1, foo2; }

Eventually I would like to pass this array to another function. However, If I actually input the above into my program, this is the result:

/home/ad/Documents> foo bar | foo1 | foo2 bar1 foo2
test1
Segmentation fault
ad@ad-laptop:~/Documents$

Thus, given where I put these debug statements, the problem is with saving the tokens? This is the first time I have worked with a 2D array so I am sure it is something wrong with my pointer logic. What can I do to fix this segmentation fault? Thanks for your time.

Code:

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>

int MAX_PATH_LENGTH = 1024; //Maximum path length to display.
int BUF_LENGTH = 1024; // Length of buffer to store user input
char * delims = "|"; // Delimiters for tokenizing user input.
const int PIPE_READ = 0;
const int PIPE_WRITE = 1;

void execute(char *args, int numPipes, int numArgs){
    int i;
    int j;
    for(i = 0; i <= numArgs; i++){
        for(j = 0; j < 25; j++){
            printf("args[%d][%d]", i, j);
        }
    }
}


void parse(char *input) { 
    char argArray[25][25];
    int numPipes = 0;
    int i = 0;
    int j = 0;
    char *tokenPtr = NULL;
    tokenPtr = strtok(input, delims);
    while(tokenPtr != NULL) {
        if(strcmp(tokenPtr, "|") == 0){ //is token a pipe?
            numPipes++;
            i++;
            j = 0;
        }
        else {
            argArray[i][j++] = *tokenPtr;
            printf("test1\n");
            tokenPtr = strtok(input, NULL);
            printf("test2\n");
        }
    }
    execute(*argArray, numPipes, i);
}

int main () {

    char path[MAX_PATH_LENGTH];
    char buf[BUF_LENGTH];
    char* strArray[BUF_LENGTH];

    while(1) {
      getcwd(path, MAX_PATH_LENGTH);
      printf("%s> ", path);
      fflush(stdout);
      fgets(buf, BUF_LENGTH, stdin);
      parse(buf);

      bzero(strArray, sizeof(strArray)); // clears array
   }
}

Answer 1

Only the first call to strtok should receive the input. Subsequent calls (while parsing the same string) should have NULL as their first argument.