[FIXED] How to redirect the output of system() called in a C program to syslog?

Issue

Inside my C code I call system to have result from a bash command.

I.e. system("ps aux | grep my_prog | head -n 1")

All is fine when I run my program in foreground mode, but in production is a service, so I need to see the output of system in syslog, not on stdout or stderr.

I'm struggling to find the best and least painful option here. Is there a proper way to do it?

Solution

The proper way is to use popen() instead of system() and then the syslog interface, man 3 syslog:

NAME
   closelog, openlog, syslog - send messages to the system logger

SYNOPSIS
   #include <syslog.h>

   void openlog(const char *ident, int option, int facility);
   void syslog(int priority, const char *format, ...);
   void closelog(void);

   #include <stdarg.h>

   void vsyslog(int priority, const char *format, va_list ap);

Also note that grepping ps output has its pitfalls (e.g. it may also return the grep process first). Why not search for the proper process in the C code iterating over ps output? Or directly iterate over the process table using functions your OS provides?

Answered By - Jens

Answer Checked By - Senaida (PHPFixing Volunteer)