getting result from 'translate' call inside C

cleopard · 08-08-2008, 07:44 AM

I have a Linux C program that, among other things, takes a string, gets rid of the invalid characters, then uses that string as a filename. I came up with a shell command using 'tr' to do what I want, but how can I call that within a C program and get a result in return? If 'exec' or similar calls are used, they don't return if they are successful.

Thank you.

tronayne · 08-08-2008, 08:15 AM

What you do is check for a non-zero value (the exec functions return -1 if unsuccessful) and deal with that. Something like

Code:

do something
if (exec (arguments)) {
    (void) fprintf (stderr, "exec failed\n");
    exit (EXIT_FAILURE);
}
do something else

cleopard · 08-08-2008, 08:39 AM

But if I 'exec'ed a 'tr' command on a string, I still wouldn't be able to get the resulting string; I'd just be finding out if the command was successful or not.

tronayne · 08-08-2008, 01:22 PM

Why not include a redirect into a file in /tmp then open that and see what you got? That ought to be quick and easy.

On another hand, rather than using one of the exec functions, why not parse the string and get rid of the blanks, backslants, slashes, carets and all the other junk folks seem to feel it necessary to type in things? That's a pretty straight-forward proposition and you can actually control what happens as you go. Something like set a pointer to the beginning of the string and character-by-character see what's there and either change it to what you want or just ignore it might just be the berries.

smoked kipper · 08-08-2008, 01:49 PM

If you need to capture the output of a command, that's what pipes are for. man 2 pipe.