Linux / UNIX: Check If File Is Empty Or Not Using Shell Script

Posted on in Categories last updated July 3, 2010

How do I check if file is empty or not using bash or ksh shell script under UNIX / Linux / OS X / BSD operating systems?

You can use the find command as follows. The -s option to the test builtin check to see if FILE exists and has a size greater than zero. It returns true and false values to indicate that file is empty or has some data.

touch /tmp/file1
ls -l /tmp/file1
find /tmp -empty -name file1

Sample outputs:

/tmp/file1

Now create another file with some data in it:

echo "data" > /tmp/file2
ls -l /tmp/file2
find /tmp -empty -name file2

You should not see any output.

Shell -s option

However, use can pass -s option as follows in script or shell prompt:

touch /tmp/f1
echo "data" >/tmp/f2
ls -l /tmp/f{1,2}
[ -s /tmp/f1 ] 
echo $?

Sample outputs:

1

The non zero output indicate that file is empty.

[ -s /tmp/f2 ]
echo $?

Sample outputs:

0

The zero output indicate that file is not empty. So you can write a shell script as follows:

Shell Script To Check If File Is Empty OR Not

#!/bin/bash
_file="$1"
[ $# -eq 0 ] && { echo "Usage: $0 filename"; exit 1; }
[ ! -f "$_file" ] && { echo "Error: $0 file not found."; exit 2; }
 
if [ -s "$_file" ] 
then
	echo "$_file has some data."
        # do something as file has data
else
	echo "$_file is empty."
        # do something as file is empty 
fi

Run it as follows:
chmod +x script.sh
./script.sh /etc/resolv.conf

Sample outputs:

/etc/resolv.conf has some data.

Run it on an empty file:
touch /tmp/test.txt
./script.sh /tmp/test.txt

Sample outputs:

test.txt is empty.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

6 comment

  1. @Vivan

    You need to edit the script:

    #!/bin/bash
    [ $# -eq 0 ] && { echo "Usage: $0 file1 file2 fileN"; exit 1; }
    for _file in $@
    do
    [ ! -f "$_file" ] && { echo "Error: $_file file not found."; continue; } 
    if [ -s "$_file" ]
    then
    	echo "$_file has some data."
            # do something as file has data
    else
    	echo "$_file is empty."
            # do something as file is empty 
    fi
    done

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