#!/usr/bin/env bash

# @(#) (calculated)     Demonstrate checksum as script name.

LC_ALL=C ; LANG=C ; export LC_ALL LANG
pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
em() { pe "$*" >&2 ; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
# C=$HOME/bin/context && [ -f $C ] && $C

# Calculate checksum, compare with name.
program=$( basename $0 )
checksum=$( cksum < $0 )
name=$( echo "$checksum" | sed 's/ /_/' )

# Intermediate output if debugging.
db " program name        = $program"
db " calculated checksum = $name"

if [ "$name" != "$program" ]
then
  db " Checksums [ $name | $program ] do not match, aborting."
  em " Checksums [ $name | $program ] do not match, aborting."
  exit 1
else
  db " Checksums [$name] match, continuing."
fi

echo ""
echo " Hello, world from $program."

exit 0

$ ./s1
 Checksums [ 2207913779_881 | s1 ] do not match, aborting.

cp s1 2207913779_881

$ ./2207913779_881 

 Hello, world from 2207913779_881.

# @(#) (calculated) Demonstrate checksum as script name;

$ ./2207913779_881 
 Checksums [ 1941515329_881 | 2207913779_881 ] do not match, aborting.