Linux / UNIX: Check If File Is Empty Or Not Using Shell Script nixCraft Updated Tutorials/Posts

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

You can use the find command and other options 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. This page shows how to check if a file is empty in Bash shell running on a Linux or Unix-like operating systems.

Check If File Is Empty Or Not Using Shell Script

The syntax is as follows:

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 from the find command.

Bash Script – Check If File is Empty or Not With the -s Option

However, one can pass the -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
Bash Shell Check If File Is Empty Or Not on a Linux/Unix
Bash Script/Command – Check If File is Empty or Not

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.

Conclusion

This page showed how to check if file is empty on a Linux or Unix-like operating systems using various commands. See test command for more info.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

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