How do i add up all elements of a command line argument-CodePudding

here is my code

#include <stdio.h>
#include <stdlib.h>

int main(int argc,char* argv[])
{
    int a;
    for(int i=1;i<=argc;i  ){
        a =atoi(argv[i]);
    }
    printf ("%d",a);
}

I keep getting segmentation faults but i am trying to add up all elements of the command line so for example ./a.out 5 6 7 would give 18 as the output, cheers.

CodePudding user response：

The problem (with the crash) is the loop itself:

for(int i=1;i<=argc;i  )

The argc argument is the number of arguments passed to the program, including the "program name" at argv[0]. So valid indexes for the actual arguments are argv[1] to argv[argc - 1].

Furthermore the argv array is terminated by a null pointer, which will be at argv[argc].

Since you include argv[argc] in your loop you pass a null pointer to atoi which leads to undefined behavior and likely crashes.

The simple solution is to use less-than < instead of less-than-or-equal as the loop condition:

for(int i=1;i<argc;i  )

CodePudding user response：

You never initialized a to 0. Also, use strtol() function.

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv) {
    int a = 0;
    for (int i = 1; i < argc; i  ) {
        a  = strtol(argv[i], NULL, 10);
    }
    printf("%d\n", a);
    return EXIT_SUCCESS;
}