Bash script; how to use vars and funcs defined after command

Question

How to use variables or functions that are defined after the command.

Variable

#!/bin/bash

echo Hello "$who"
who="World"

Function

#!/bin/bash

function_name

function_name() {
echo Hello World
}

I also heard there is a command to read entire bash script before executing any commands, this would work for my case. But it would be nice if there is a more pinpoint way.

More in-depth

#!/bin/bash

h=Hello

echo $h "$who"

var1=World

who=$(cat <<HEREDOC
You
Me
$var1
HEREDOC
)

You can't declare and use functions before the definition like you can in C. Why are you trying to do this? Do you just want the functions/variables defined at the end of the script for readability? — that other guy
– that other guy, Commented May 19, 2016 at 23:13
@thatotherguy You are correct, I have a heredoc in the script and would like it to be below the command. — SongJaeGu
– SongJaeGu, Commented May 19, 2016 at 23:15
I don't follow. Do you have a here doc with variables in it, and you want the variables to be defined further down? Can you just use functions, like main() { echo "Hello $who"; }; ...; who="world"; main ? — that other guy
– that other guy, Commented May 19, 2016 at 23:19
@thatotherguy You are correct again, I want variables in the here doc and generally just at the bottom of the command for readability. Both the command and here doc are large... Also to note, I do have vars before the command and I don't want to point to an external doc. — SongJaeGu
– SongJaeGu, Commented May 19, 2016 at 23:33
Would using a method like I suggested be an option? There's no way to get around the fact that you have to define functions/variables before they're used, but you can control flow in those kinds of ways — that other guy
– that other guy, Commented May 19, 2016 at 23:45

that other guy · Accepted Answer · 2016-05-20 00:20:32Z

2

Variables and functions always have to be defined before use. This is because function definitions are actually commands that assign the name in the current context, and not like in C where they merely provide an implementation for a name.

You can instead use control flow to ensure that the definitions execute before your code, regardless of their relative layout in the file:

main() {
  echo "Hello $var"
}

var="world"
main

edited May 20, 2016 at 0:20

answered May 20, 2016 at 0:11

that other guy

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