check if a file is empty in shell script

A shell script (isEmpty.sh) example to check if a file is empty or not.

#!/bin/sh
f='afile.txt'

hasData ()
{
	echo "$f has data."
	ls -l $f
	cat $f
}

noData()
{
	echo "$f is empty."
	ls -l $f
}

if [[ -s $f ]]
then
	hasData
else
	noData
fi

The text file afile.txt

hello world

The output when the file has data

afile.txt has data.
-rw-r--r--+ 1 username  941854322  12 Jan 17 11:31 afile.txt
hello world

The output when the file is empty.

afile.txt is empty.
-rw-r--r--+ 1 username  941854322  0 Jan 17 11:37 afile.txt

The run the script.

chmod +x isEmpty.sh
./isEmpty.sh