shell

• Filename

• Pattern Matching

• Operations on variables

• heredoc

Filename

cmd	result
$0	./t.sh
$(basename $0)	t.sh
$(basename $0 .sh)	t
${PWD##*/}	parent_dir_name

Pattern Matching

https://www.gnu.org/software/bash/manual/html_node/Pattern-Matching.html

Operations on variables

https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html#Shell-Parameter-Expansion

type	example	result	More
Length	echo ${#SHELL}	9
${parameter:-$var}	${NULL:-$SHELL}	/bin/bash
${parameter:-word}	echo ${SHELL:-ignored}	/bin/bash	[ -z "${COLUMNS:-}" ] && COLUMNS=80 ; echo $COLUMNS
${parameter:=word}	unset a ; echo ${a:=b} ; echo $a	b b
${VAR:OFFSET:KEEP}	echo ${SHELL:0:4}	/bin
${VAR/PATTERN/NEW}	echo ${SHELL/b/}	/in/bash
${VAR//PATTERN/NEW}	echo ${SHELL//b/}	/in/ash
${VAR#beginning}	echo ${SHELL#*/}	bin/bash
${VAR##beginning}	echo ${SHELL##*/}	bash
${VAR%trailing}	${SHELL%/*h}	/bin

heredoc

https://en.wikipedia.org/wiki/Here_document#Unix_shells