Programming

(using C) I'm getting really frustrated because I feel what I'm trying to do is easy as pie but I can't think of it. I'm reading in a file that contains a list of commands (ie- wc -cl ls, etc), one per line, and I need to execute those commands on the cwd. I'm used to C++ so I'm having problems reading in the commands properly. And the exec that I'm using I'm pretty sure isn't the right one. I've tried other exec's but they give me errors.

int count;
int fin;
char test[10];

if ( (fin = open ( argv[1], O_RDONLY)) == -1) {
printf("\nError in opening file:\n");
perror ("Error:");
close(fin);
return 1;
}

while ((count=read(fin, test, 256)) > 0 ) {
printf ("%s\n", test); //used this to show something was read in
}
exec (test, cwd) > out.txt //exec the commands read on cwd, send
//output to out.txt

Quick example using a file with tab separated command and single argument. untested, but should get across the basic idea.

Code:

int main(int argc, char **argv<) {
pid_t chld;
char line[256];
char cmd[256], arg[256];
FILE *fd;

                    if (argc != 2) {printf("Error: You must provide a filename for this program.\n"); return -1;}
                    
                   if ( (fd = fopen(argv[1],"r")) == NULL) {return -1;}
                   while (fgets(line,256,fd) != NULL) {
                           if (sscanf(line,"%s\t%s",cmd,arg) != 2) {continue;}
                           if ( (chld = fork()) == 0) {
                             execl(basename(cmd),cmd,arg,NULL);
                           } else if (chld > 0) {
                              wait(NULL);
                           }
                           chld = 0;
                    }
                   fclose(fd);
                   return 0;
}

Simpler version would be to use the system() call.
If it makes senese to do this, and the file you are reading has the execute attribute set
you could

Code:

system("/path/to/filename");

Yes. System performs the gyrations in my example and more transparently. Good catch Jim.

Thanks guys. I think I was using too few arguments in my exec statement and I think I swapped some arguments in the fgets. you guys cleared up a lot of confusion, Thanks a lot!!