about "Create Process", how to get the return status?

iclinux · 01-12-2005, 12:09 AM

with "system(COMMAND)", we can get the return status of COMMAND.

Then, what about fork, execvp, can they get the return status?

///////////////////////////////////////////////////////////////////////////
the follow is some code, but it doesn't get the return value:
///////////////////////////////////////////////////////////////////////////
int spawn (char* program, char** arg_list)
{
pid_t child_pid;

/* Duplicate this process. */
child_pid = fork ();
if (child_pid != 0)
/* This is the parent process. */
return child_pid;
else {
/* Now execute PROGRAM, searching for it in the path. */
execvp (program, arg_list);
/* The execvp function returns only if an error occurs. */
fprintf (stderr, "an error occurred in execvp\n");
abort ();
}
}

randyding · 01-12-2005, 12:50 AM

Code:

//Unix version
//returns 1 on success, 0 on failure
//
int fork_exec_wait(char *cmd,       //duplicate this in argv[0]
                   char *argv[],    //last argv[] must be NULL
                   const char *type,//"", "p" = use path env. variable
                   int *result,     //can be NULL
                   int *fd_to_close_in_child,        //[in], array of fd
                   int fd_to_close_in_child_count)   //number of valid fd
{
    pid_t pid;
    int j, status;


    assert(cmd);
    assert(argv);
    assert(type);
    assert(!fd_to_close_in_child_count || fd_to_close_in_child);
    if (!cmd || !argv || !type) return 0;
    if ((pid=fork())<0) return 0;
    if (!pid) {
        //child continues
        for (j=0; j<fd_to_close_in_child_count; j++)
            if (fd_to_close_in_child[j]) close(fd_to_close_in_child[j]);
        if (strstr(type,"p")) execvp(cmd, argv);
        else execv(cmd, argv);
        _exit(127); //execv() failed
    }
    //parent continues
    while (waitpid(pid,&status,0)<0) if (EINTR!=errno) return 0;
    if (result) {
        if (WIFEXITED(status)) *result=WEXITSTATUS(status);
        else *result=255;
    }
    return 1;
}    //fork_exec_wait()

iclinux · 01-12-2005, 08:02 PM