check if file is empty

Shell Programming and Scripting
1

How do I check if a file is empty in a sh script

I want to test in my shell script if the output file is empty and if it is do one thing and if it isnt empty do another?

any ideas?

2

Read the man pages of test

       -s FILE
              FILE exists and has a size greater than zero

Within a script it would take this form.

#! /bin/ksh

if [[ -s $FILE ]] ; then
echo "$FILE has data."
else
echo "$FILE is empty."
fi ;

vino

3

an exit status of 1 indicates that the FILE is empty or the file does not exist.....

$ ls
$ touch file_1
$ dd if=/dev/zero of=$HOME/tmp/file_2 bs=1 count=100
100+0 records in
100+0 records out
$ ls -l file_1 file_2 file_3
ls: file_3: No such file or directory
-rw-rw-r--  1 foo bar   0 Sep 24 20:28 file_1
-rw-rw-r--  1 foo bar 100 Sep 24 20:28 file_2
$ [[ -s file_1 ]]
$ echo $?
1
$ [[ -s file_2 ]]
$ echo $?
0
$ [[ -s file_3 ]]
$ echo $?
1

Cheers
ZB

4

A sleek 'n' smart solution !! :cool:

5

this is just another way of doing it

a round about one

if [ `ls -l <file> | awk '{print $5}'` -eq 0 ]
then
//condition for being empty
else
//condition for not being empty
fi

better way of doing is using the -s option of test

6

All worked as I required -s FILE option was the solution I used in my script and now I am a happy man.

7

I have a requirement where if file size is 487 then ignore it otherwise put into e-mail script? I can do it using -s but it does only if file is empty...
any clue on this please???

8 
FILE="path of your file"
FILESIZE="`du -b $FILE | sed 's:^\([0-9]*\)*[[:space:]]*.*:\1:'`" 

if [ "$FILESIZE" = "487" ];then
 echo "$FILE has size 487 bytes"
else
 echo "Some other filesize"
fi

In place of '=' you can use '-gt' '-lt' '-gte' '-lte' for greater than, less than, greater than or equal to, less than or equal to.

9

The -b option to du is not standard. The usual command to use is wc:

filesize=$( wc -c < "$FILE" )

It's -le not -lte, and -ge not -gte.