bash use cases

check for program existing

command -v foo >/dev/null 2>&1 || { echo >&2 "I require foo but it's not installed.  Aborting."; exit 1; }
type foo >/dev/null 2>&1 || { echo >&2 "I require foo but it's not installed.  Aborting."; exit 1; }
hash foo 2>/dev/null || { echo >&2 "I require foo but it's not installed.  Aborting."; exit 1; }

# http://stackoverflow.com/questions/592620/how-to-check-if-a-program-exists-from-a-bash-script

confirmation

read -p "Are you sure? " -n 1 -r
echo    # (optional) move to a new line
if [[ $REPLY =~ ^[Yy]$ ]]
then
    # do dangerous stuff
fi
# http://stackoverflow.com/questions/1885525/how-do-i-prompt-a-user-for-confirmation-in-bash-script

microshell (e.g. dict)

#!/bin/bash
while :
do
	echo "Press [CTRL+C] to stop..."
	read -p "dict>" -r
	dict $REPLY
done
 
# oneliner
while :; do echo "Press [CTRL+C] to stop..."; read -p "dict>" -r; dict $REPLY; done
 
# silent oneliner
while :; do read -p "dict>" -r; dict $REPLY; done
 
# chronic oneliner (save prompted words in bash_history)
while :; do read -p "dict>" -r; dict $REPLY; history -s "dict $REPLY"; done
 
# $# chronic oneliner example
# $while :; do read -p "dict>" -r; dict $REPLY; history -s "dict $REPLY"; done
# dict>sex
# dict>^C
# $ history
#  1  # chronic oneliner example
#  2  dict sex
#  3  dict
#  4  history
# $