mkscript.sh

#!/bin/sh
#
# NAME: mkscript
# Description: Creates a basic script using itself as a template
# Created: 2013-09-12
# Updated: 2018-06-02
# Version: 0.14.2
# Copyright (C) Brendan Hide 2013-2018
# License: MIT License (Expat)
#        See https://opensource.org/licenses/MIT and https://en.wikipedia.org/wiki/MIT_License
#        Remember to update the Copyright and Author(s) lines to include principal authors/owners/etc
# TODO:  Set dates automatically
#        Allow template variable choices (compatible licenses perhaps?, copyright, mutex, etc)
#        Allow Mutex to wait instead of quit
#        Automatically detect interactive shell and Ignore Delay appropriately
#
#====================# WARNING #=====================#
# DO NOT EDIT THIS FILE DIRECTLY IF IT IS STORED     #
# USING A CENTRAL REPOSITORY. YOUR CHANGES WILL BE   #
# OVERWRITTEN! INSTEAD, MAKE CHANGES AT THE PATH     #
# SPECIFIED BELOW.                                   #
#====================# WARNING #=====================#
#
# Central Repository Path: 
# https://gist.github.com/zatricky/
#
# Author(s): Brendan Hide / zatricky
set -u #nounset - quit on any use of a variable that has not been initialised
set -e #noerror - quit on any error
#set -x #debug mode

## Initialize variables
SELF=${0##*/}
FULLSELF=$(dirname ${0})/$SELF
SHA2SELF=$(echo ${FULLSELF} | openssl sha256 | awk '{print $2}')
LOCKFILE=/tmp/${SELF}.${SHA2SELF}.lock
MUTEX="false"
DELAYMAX=0 #Set a random delay in seconds before executing main()

#TMP is updated later with the mutex checks. We define it here in advance as we'd like to use it within main()
TMP=""

main(){
	if [ ${#} -lt 1 ] ; then
  echo "Error. Please specify the destination file."
		exit 1
	fi
 newscript=${1}
 if [ -f ${newscript} ] ; then
  echo "Error. Refusing to overwrite ${newscript}."
		exit 1
 else
  if ( set -o noclobber; cat ${FULLSELF} > ${newscript} ) ; then
   chmod +x ${newscript}
  else
   echo "Error writing to ${newscript}."
  fi
 fi

}

cleanup(){
 #This step is for the (however unlikely) case that a filesystem might be
 #mounted within our temporary folder. If we don't do this, the step
 #thereafter will delete all content in the mounted filesystem.
 while true ; do
  mount | grep ${TMP} || break
  for i in $(mount | grep ${TMP} | awk '{print $3}') ; do
   umount ${i}
  done
 done

 #Remove TMP
 rm ${TMP} -rf

}

#Leave this here for Debug
echo "STARTING ${0}" > /dev/null
echo $(date "+%Y-%m-%d-%Hh%Mm%Ss%z") > /dev/null

#Pseudo-random delay applicable to cluster/parallel operations
if ! [ ${DELAYMAX} -eq 0 ] ; then
 wait_time=$$
 wait_time=$((wait_time % DELAYMAX))
 sleep ${wait_time}
fi

#Capture current date
STARTDATE=$(date "+%Y-%m-%d - %Hh%M")
NUMDATE=$(date "+%s")
ISO_DATE_SECONDS=$(date -Is)

#Prevent $SELF from running simultaneously
if [ "${MUTEX}" = true ] ; then
 if [ -f "${LOCKFILE}" ] ; then
  other_pid=$(cat "${LOCKFILE}")
  if [ "$?" != 0 ]; then
   # existing pid file does not exist - probably being deleted by existing process that is finishing up
   echo "SKIPPED running ${SELF} due to existing process busy with cleanup" > /dev/null
   exit 0
  fi
  if grep ${SELF} /proc/${other_pid}/cmdline > /dev/null ; then
   # appears to be running already. checkall skipped
   echo "SKIPPED running ${SELF} due to existing process" > /dev/null
   exit 0
  else
   #We reach this point only if the file exists but that instance is actually dead/not running. We can safely remove the lock file
   rm -f ${LOCKFILE}
  fi
 fi

 #We use an atomic mutex check in case multiple instances did the above check simultaneously
 if ( set -o noclobber; echo $$ > "${LOCKFILE}") 2> /dev/null ; then
  #We don't use rm -rf as it has the danger of deleting our entire filesystem in the rare case that the unmount fails
  trap 'rm -f "${LOCKFILE}"; cleanup ; exit $?' INT TERM EXIT

  TMP=$(mktemp -d)

  #Run!
  main $*

  #Close off the trap
  rm -f ${LOCKFILE}
  #Remove TMP
  cleanup
  trap - INT TERM EXIT

  #Leave this here for Debug
  echo "FINISHED running ${0}" > /dev/null
  echo $(date "+%Y-%m-%d-%Hh%Mm%Ss%z") > /dev/null

 else
  #Leave this echo here for Debug
  echo "SKIPPED running ${SELF} due to existing process" > /dev/null
  echo $(date "+%Y-%m-%d-%Hh%Mm%Ss%z") > /dev/null
 fi
else # Skip Mutex checks
 #Create TMP
 TMP=$(mktemp -d)

 main ${*}

 #Remove TMP
 cleanup

 #Leave this here for Debug
 echo "FINISHED running ${0}" > /dev/null
 echo $(date "+%Y-%m-%d-%Hh%Mm%Ss%z") > /dev/null

fi