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Variable

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Builtin ​

VariableDescription
$?Return code of last command.
$#Number of arguments.
$@All Arguments.
$1Argument 1 (usable: 0-9).

String ​

shell
myvar="value"

Array ​

Creation:

shell
names=('My name' 'Your name' 'Their name')
read -ra state < <(echo '1 2 3')  # From output

Access elements:

shell
echo "${names[@]}"  # All elements
echo "${names[1]}"  # Index (start from 0)

Length:

shell
echo "${#names[@]}"

Advanced syntax ​

To lower case:

shell
name="Sora"
echo "${name,,}"

Remove trailing character (slash):

shell
SOME_DIR="some_dir/"
echo "${SOME_DIR%/}"