Question

pid_t childPid = fork ();
if (childPid == (pid_t) 0)//zero success
{
    const char *path = "/usr/local/mysql/bin/mysql";
    //doesn't work
    //char * const parmList[] = {"--user=root", "test_db", NULL};
    //does work
    char * const parmList[] = {"", "--user=root", "test_db", NULL};
    execv(path, parmList);
    printf("ERROR:\tFork failed.\n");   
}
else if (childPid < (pid_t) 0)// -1 failure
{
    /* The fork failed. */
    printf("ERROR:\tFork failed.\n");   
    return EXIT_FAILURE;
}
else
{
    while (true) {
        //stay alive
        sleep(1);
    }
}
printf("done");
exit(0);

I am having trouble importing a sql dump by using execv. You can see I wasn’t able to login using the first paramList but the second one worked just fine. Anyways, if I add to the param list:

char * const parmList[] = {"", "--user=root", "test_db", "<", "/Users/joelsaltzman/Desktop/dump.sql", NULL};

The output shows the mysql help for the command line args like I typed something wrong.
Does anybody know how to get this to work?

Answer 1

The first paramList is incorrect, because the first element should be the filename of the program you are going to execute:

The argument argv is an array of character pointers to null-terminated strings. The application shall ensure that the last member of this array is a null pointer. These strings shall constitute the
argument list available to the new process image. The value in argv[0] should point to a filename that is associated with the process being started by one of the exec functions.

The input redirection with < does not work because this is not a feature of the kernel (which you invoke using execv), but of usual Unix shells. The system library call is what you are looking for. (It also just uses a call from the exec-family, but calls a shell with your command, which will then support <.)

Be sure to read the manpage system(3) and think about input validation if you are going to pass it a string that could be influenced by a malicious user.