Using exec() functions to Call Linux Command in C

Question

I've been stuck trying to do this for a while now, and I just cannot get it to work no matter what I try.

My C code looks like this:

char *const parmList[] = {"ps","-o pid",processID,NULL};
execvp("/bin/ps", parmList);

What am I doing wrong?

What is the type of processID? If it is a string that contains the PID, you'll be fine. If it is an integer, then you will have problems — it should be a string; all arguments to a command are strings. And, FWIW, the command as written would work on Mac OS X, but fails on Linux with error: improper format list (but on Linux, you could use ps -opid,ppid,time with no space between the -o and the list of columns to be printed, or with two separate arguments). — Jonathan Leffler
– Jonathan Leffler, Commented Sep 27, 2015 at 2:29

MikeCAT · Accepted Answer · 2015-09-27 02:16:21Z

3

Not tested, I think you are executing

ps "-o pid,ppid,time" 3817

Try this:

char *const parmList[] = {"ps","-o","pid,ppid,time",processID,NULL};
execvp("/bin/ps", parmList);

answered Sep 27, 2015 at 2:16

MikeCAT

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