At work, I write bash scripts frequently. My supervisor has suggested that the entire script be broken into functions, similar to the following example:
#!/bin/bash
# Configure variables
declare_variables() {
noun=geese
count=three
}
# Announce something
i_am_foo() {
echo "I am foo"
sleep 0.5
echo "hear me roar!"
}
# Tell a joke
walk_into_bar() {
echo "So these ${count} ${noun} walk into a bar..."
}
# Emulate a pendulum clock for a bit
do_baz() {
for i in {1..6}; do
expr $i % 2 >/dev/null && echo "tick" || echo "tock"
sleep 1
done
}
# Establish run order
main() {
declare_variables
i_am_foo
walk_into_bar
do_baz
}
main
Is there any reason to do this other than "readability", which I think could be equally well established with a few more comments and some line spacing?
Does it make the script run more efficiently (I would actually expect the opposite, if anything), or does it make it easier to modify the code beyond the aforementioned readability potential? Or is it really just a stylistic preference?
Please note that although the script doesn't demonstrate it well, the "run order" of the functions in our actual scripts tends to be very linear -- walk_into_bar depends on stuff that i_am_foo has done, and do_baz acts on stuff set up by walk_into_bar -- so being able to arbitrarily swap the run order isn't something we would generally be doing. For example, you wouldn't suddenly want to put declare_variables after walk_into_bar, that would break things.
An example of how I would write the above script would be:
#!/bin/bash
# Configure variables
noun=geese
count=three
# Announce something
echo "I am foo"
sleep 0.5
echo "hear me roar!"
# Tell a joke
echo "So these ${count} ${noun} walk into a bar..."
# Emulate a pendulum clock for a bit
for i in {1..6}; do
expr $i % 2 >/dev/null && echo "tick" || echo "tock"
sleep 1
done
main()at the top and addmain "$@"at the bottom to call it. That lets you see the high level script logic first thing when you open it. – John Kugelman yesterdaylocal- this provides variable scope which is incredibly important in any non-trivial script. – Boris the Spider yesterday