execvp is not accepting all the argument list from ps -u command

Question

Hello so I'm trying to read the all the PID from already executing processes with a specific name, saving does PID for later kill does process with a signal alarm every 45 seconds.

The problem comes when executing the execvp with the following parameters:

char* command = "ps"; char* argument_list[] = {"ps ", "-u|grep 'NAME_PROCESS'|grep -v 'grep'|awk '{print $2}'", NULL};

int status_code = execvp(command, argument_list);

The error that shows up is the following:

error: user name does not exist

Usage: ps [options]

Try 'ps --help <simple|list|output|threads|misc|all>' or 'ps --help <s|l|o|t|m|a>' for additional help text.

For more details see ps(1).

Answer 1

You can use shell metacharacters but you need to invoke the shell explicitly and pass the entire command line as a single string (untested)...

const char *command = "sh";
char *argument_list[] = {
    "sh", "-c", "ps -u | grep 'NAME_PROCESS' | grep -v 'grep' | awk '{print $2}'", NULL
};
execvp(command, argument_list);