how to use exec() to run a c program from another c program

Question

i've been trying to use execvp to run ac program but it always seems to fail.

from main.c

int main() {
char* args[] = {"2", "1"};
    if(execvp("trial.c", args) == -1) {
        printf("\nfailed connection\n");
    }

from trial.c

int main(int argc, char** argv){
printf("working");
return 1;
}

I think i tried every way to possibly represent that file location in the exec() and it always results in "failed connection".

Answer 1

The first parameter to execvp expects the name of an executable file. What you've passed it is the name of a source file. You need to first compile trial.c, then pass the name of the compiled executable to execvp .

Regarding the second parameter to execvp , the last element in the array must be NULL . That's how it knows it reached the end of the list. Also, by convention the first parameter to a program is the name of the program itself.

So first compile trial.c:

gcc -g -Wall -Wextra -o trial trial.c

Then modify how to call it in main.c:

int main() {
    char* args[] = { "trial", "2", "1", NULL };
    if(execvp("trial", args) == -1) {
        printf("\nfailed connection\n");
    return 1;
}

Answer 2

First argument for execvp is path to executable. You need to build the executable for trial.c and pass the path of the executable to execvp .

if(execvp("---path to executable---/ExecTrial", args) == -1) {
    printf("\nfailed connection\n");
}

If you don't pass the executable path, execvp will search the executable in the colon-separated list of directory pathnames specified in the PATH environment variable.

Answer 3

If you're trying to call execvp() on a source file then this is not what this function does. The first argument is expected to be a path of an executable. If you want to run the program which trial.c is the source of, you should build (compile and such) it first. For example like this:

$ gcc -o trial trial.c 

Then call execvp() on the your newly created executable instead of the source file:

if(execvp("trial", args) == -1) { //...

Answer 4

trial.c is not a valid executable file. C is not a scripting or interpreted language; you cannot run C source files directly. AC program must be compiled and linked into an executable.