Shell Scripting Cheat Sheet

Quick reference for writing reliable Bash scripts.

Variables and Parameters

# Variable assignment (NO spaces around =)
NAME="World"
echo "Hello $NAME"

# Command substitution
TODAY=$(date)

if [ -z "$VAR" ]; then
    echo "Variable is empty"
elif [ "$VAR" == "test" ]; then
    echo "Variable is test"
else
    echo "Something else"
fi

Operator	True if...
`-f file`	File exists and is a regular file.
`-d dir`	Directory exists.
`-s file`	File exists and is not empty.
`-x file`	File is executable.

For Loop:

for item in apple banana cherry; do
    echo "I like $item"
done

While Loop:

count=1
while [ $count -le 5 ]; do
    echo "Count: $count"
    ((count++))
done

my_function() [
    echo "First argument: $1"
    return 0
]
# Call it
my_function "Hello"

(Note: brackets used instead of literal braces for documentation compatibility)