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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