Bash Cookbook

How to do it...

Let's start our activity as follows:

1. Open a new terminal and create a new script by the name of mylock.sh with the following contents:

#!/bin.bashLOCKFILE="/tmp/mylock"function setup() {   # $$ will provide the process ID  TMPFILE="${LOCKFILE}.$$"  echo "$$" > "${TMPFILE}"    # Now we use hard links for atomic file operations   if ln "${TMPFILE}" "${LOCKFILE}" 2>&- ; then      echo "Created tmp lock"  else      echo "Locked by" $(<$LOCKFILE)      rm "${TMPFILE}"      exit 1  fi  trap "rm ${TMPFILE} ${LOCKFILE}" SIGINT SIGTERM SIGKILL}setupecho "Door was left unlocked"exit 0

2. Execute the script with the $ bash mylock.sh script and review the console's output.
3. Next, we know that the script is looking for a particular lock file. What happens when we create ...