panel 1: defining functions is easy

say_hello() {
    echo "hello!"
}

and so is calling them:

say_hello

(no parentheses when calling a function!

panel 2: functions have exit codes

failing_function () {
    return 1
}

0 is a success, everything else is a failure. A program’s exit codes work the same way – 0 is success, everything else is failure.

panel 3: you can’t return a string

you can only return an exit code from 0 to 255

panel 4: arguments are $1, $2, $3, etc

say_hello() {
    echo "Hello, $1!"
}
say_hello "Ahmed"

the above code prints Hello, Ahmed!. Again, say_hello "Ahmed", not say_hello("Ahmed")

panel 5: The local keyword declares local variables

say_hello() {
    local x
    x=$(date) # this is a local variable
    y=$(date) # this is a global variable
}

panel 6: local x=VALUE suppresses errors

this line never fails, even if asdf doesn’t exist:

local x=$(asdf)

but this will fail (as you would expect) – if you have set -e set, it’ll stop the program

local x
x=$(asdf) # this line will fail

person: “I really have NO IDEA why it’s like this, bash is weird sometimes”