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 "${ARR[@]^}" # => Hello World
Bash Parameter expansions
Transform
basepath & dirpath
SRC="/path/to/foo.cpp"
BASEPATH=${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
See: Parameter expansion
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
Syntax
| Code | Description |
|---|---|
${FOO%suffix} |
Remove suffix |
${FOO#prefix} |
Remove prefix |
${FOO%%suffix} |
Remove long suffix |
${FOO##prefix} |
Remove long prefix |
${FOO/from/to} |
Replace first match |
${FOO//from/to} |
Replace all |
${FOO/%from/to} |
Replace suffix |
${FOO/#from/to} |
Replace prefix |
#Substrings
| Expression | Description |
|---|---|
${FOO:0:3} |
Substring (position, length) |
${FOO:(-3):3} |
Substring from the right |
#Length
| Expression | Description |
|---|---|
${#FOO} |
Length of $FOO |
#Default values
| Expression | Description |
|---|---|
${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 |
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