mjhjmtu

The script is called isFile.sh and looks like this:

#!/bin/sh

echo $1
echo $2

if [ ! -f $1 ]; then
 echo "$1 (arg1) is not a file"
fi

if [ ! -f $2 ]; then
 echo "$2 (arg2) is not a file"
fi

First I created a file by doing touch file.exist.

And I ran bash isFile.sh file.exist file.notexist
The output was:

file.exist

file.notexist

file.notexist (arg2) is not a file

Then I ran bash isFile.sh "" file.notexist
The output was:

(# empty line)

file.notexist

file.notexist (arg2) is not a file

Expected output is:

(# empty line)

file.notexist

(arg1) is not a file

file.notexist (arg2) is not a file

Can somebody explain why?

The issue is that [ ! -f $1 ] becomes [ ! -f ] after expansion (and not [ ! -f "" ] as you thought!), so instead if checking if a given file exists, [ checks if the -f string is empty or not. It's not empty, but thanks to ! the final exit code is 1, thus the echo command is not executed.

That's why you need to quote your variables in POSIX shells.

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