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
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.
