Question

I am using one system call in my c code

#include <sys/stat.h>
#include <stdio.h>

int
main(int argc, char *argv[])
{
    int a = system("./test12.out");  //here if i give any wrong command
    system("echo $?")
    printf("system return is %d",a);
}

there isn’t any test12.out file in my current folder. Now output is

sh: ./test12.out: No such file or directory
0
system return is 32512

Here is my shell command failed but how can I know that in my c code?

Edit:

So, can I do this

int main(int argc, char *argv[])
{
    int a = system("dftg");

    if(a == -1)
        printf("some error has occured in that shell command");
    else if (WEXITSTATUS(a) == 127)
        printf("That shell command is not found");
    else
        printf("system call return succesfull with  %d",WEXITSTATUS(a));
}

Answer 1

If a == -1, the call has failed. Otherwise, the exit code is WEXITSTATUS(a).

To quote man 3 system:

RETURN VALUE
       The value returned is -1 on  error  (e.g.   fork(2)  failed),  and  the
       return  status  of the command otherwise.  This latter return status is
       in the format specified in wait(2).  Thus, the exit code of the command
       will  be  WEXITSTATUS(status).   In case /bin/sh could not be executed,
       the exit status will be that of a command that does exit(127).

       If the value of command is NULL, system() returns non-zero if the shell
       is available, and zero if not.