Checking if file exists and unzipping

Shell Programming and Scripting
1

Hey, I am new to scripting and was wondering what is wrong with this if statement. I want to check if file exists and the if it does to unzip it. I program it as follows

if [ -e *_filename.gz ]; then
gunzip *_filename.gz 
fi

Thanks in advance!

2

Try -f instead:-

if [ -f *_filename.gz ]; then
3

The -f option does not work either! :frowning:

4

Works for me:-

# ls -l
-rwxr-xr-x   1 user    group         157 Nov 19 09:10 test1.gz
-rw-r--r--   1 user    group          39 Nov 19 10:39 test2.gz

# if [ -f *test*.gz ]
> then
>    echo Yes
> else
>    echo No
> fi
Yes

# rm -f *.gz
# if [ -f *test*.gz ]
> then
>    echo Yes
> else
>    echo No
> fi
No

What is your OS / Platform?

5

This will fail in many systems because -f will get confused when given more than one argument.

I'd use a for-loop instead, breaking so it only runs once. Or not, if you want to run it over all files...

for FILE in *.gz
do
        if ! [ -f "$FILE" ] 
        then
                echo "No gz files"
       fi
       echo "$FILE exists"
       break
done
1 Like
6

Or you can use ls to check:-

if [ $( ls -l *_filename.gz 2> /dev/null | wc -l ) -ne 0 ]
then
      gunzip *_filename.gz
fi
7

That is a useless use of ls *, running ls here is redundant. It will also cause error message spam when no files are present.

8

Corona688, I am redirecting error to /dev/null , BTW why ls is redundant here?

9

Because you're running an external program when there was no need to do so.

Actually, you're running two external programs when there was no need to do so, inside a subshell, so a waste of three processes as opposed to zero.

10

Got it, so actually it is not redundant but not required or inefficient. As per the page I think it is said redundant because ls is used in a for loop with *glob.

11

It's redundant because you don't actually need the ls to list the files. If you're globbing, you already have them.