13.1. Analyzing a System Script

#!/bin/sh
# --> Comments added by the author of this document marked by "# -->".
# --> This is part of the 'rc' script package
# --> by Miquel van Smoorenburg, <[email protected]>.
# --> This particular script seems to be Red Hat / FC specific
# --> (may not be present in other distributions).
# Bring down all unneeded services that are still running
#+ (there shouldn't be any, so this is just a sanity check)
for i in /var/lock/subsys/*; do
 # --> Standard for/in loop, but since "do" is on same line,
 # --> it is necessary to add ";".
 # Check if the script is there.
 [ ! -f $i ] && continue
 # --> This is a clever use of an "and list", equivalent to:
 # --> if [ ! -f "$i" ]; then continue
 # Get the subsystem name.
 subsys=${i#/var/lock/subsys/}
 # --> Match variable name, which, in this case, is the file name.
 # --> This is the exact equivalent of subsys=`basename $i`.
	
 # --> It gets it from the lock file name
 # -->+ (if there is a lock file,
 # -->+ that's proof the process has been running).
 # --> See the "lockfile" entry, above.
 # Bring the subsystem down.
 if [ -f /etc/rc.d/init.d/$subsys.init ]; then
 /etc/rc.d/init.d/$subsys.init stop
 else
 /etc/rc.d/init.d/$subsys stop
 # --> Suspend running jobs and daemons.
 # --> Note that "stop" is a positional parameter,
 # -->+ not a shell builtin.
 fi
done