分段错误（核心转储）运行时错误

Question

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <string.h>
#include <sys/types.h>

int main(int argc, char *argv[]){
    int split;
    pid_t childpid;

    char *x = argv[1];
        
    int status;
    char splitindex_string[40];
    split = atoi(x);    
    printf("%d\n" ,split );
    
    int indexfile_split = 320000/split;

    snprintf(splitindex_string,40, "%d", indexfile_split);
    
    childpid = fork();

    if(childpid==0){
        execlp("/bin/split", "split", "l", splitindex_string, "-a", "1" ,"-d", "input.txt", "output",  NULL);
        return 0;
    }

    else{
        int status;
        wait(&status);

        return 0;
    }
}

i have this c code, but when i run the output i keep getting this weird segmentation fault (core dumped) error. the code compiles fine, the error only appears after i run the binary. from what I read online im probably accessing invalid memory. Ive been staring at this for hours now. help would be appreciated thanks

Answer 1

The problem is the missed check over input. If you don't provide argument to the executable it crash, and give you the error you say.

I suggest you to introduce a check over the argument provided, before accessing them.

Answer 2

You need to check if your program is invoked correctly, for example like this:

int main(int argc, char *argv[]){
    if (argc < 2)
    {
       printf("You didn't provide enough arguments\n");
       return 1;
    }

    int split;
    pid_t childpid;
    ...

If argc <2 then argv[1] doesn't exist and dereferencing it will result in undefined behaviour.