Syntax

Syntax Description
${parameter%suffix} Remove suffix
${parameter#prefix} Remove prefix
${parameter%%suffix} Remove long suffix
${parameter##prefix} Remove long prefix
${parameter/pattern/string} Replace first pattern match with string
${parameter//pattern/string} Replace all the pattern with string
${parameter/%pattern/string} Replace suffix pattern with string
${parameter/#pattern/string} Replace prefix patter with string

Substrings

${FOO:0:3} Substring (position, length)
${FOO:(-3):3} Substring from the right

Length

${#FOO} Length of $FOO

Default values

${FOO:-val} $FOO, or val if unset
${FOO:=val} Set $FOO to val if unset
${FOO:+val} val if $FOO is set
${FOO:?message} Show message and exit if $FOO is unset

Substitution

echo ${food:-Cake}  #=> $food or "Cake"
STR="/path/to/foo.cpp"
echo ${STR%.cpp}    # /path/to/foo
echo ${STR%.cpp}.o  # /path/to/foo.o
echo ${STR%/*}      # /path/to

echo ${STR##*.}     # cpp (extension)
echo ${STR##*/}     # foo.cpp (basepath)

echo ${STR#*/}      # path/to/foo.cpp
echo ${STR##*/}     # foo.cpp

echo ${STR/foo/bar} # /path/to/bar.cpp

Basepath & Dirpath

SRC="/path/to/foo.cpp"
BASEPATH=${SRC##*/}   
echo $BASEPATH  # => "foo.cpp"

DIRPATH=${SRC%$BASEPATH}
echo $DIRPATH   # => "/path/to/"

Slicing

name="John"
echo ${name}           # => John
echo ${name:0:2}       # => Jo
echo ${name::2}        # => Jo
echo ${name::-1}       # => Joh
echo ${name:(-1)}      # => n
echo ${name:(-2)}      # => hn
echo ${name:(-2):2}    # => hn

length=2
echo ${name:0:length}  # => Jo

Transform

STR="HELLO WORLD!"
echo ${STR,}   # => hELLO WORLD!
echo ${STR,,}  # => hello world!

STR="hello world!"
echo ${STR^}   # => Hello world!
echo ${STR^^}  # => HELLO WORLD!

ARR=(hello World)
echo "${ARR[@],}" # => hello world
echo "${ARR[@]^}" # => Hello World

<aside> 💡 Read more about bash parameter expansions here:

</aside>