Checking if a file is readable and exists in one if condition: if [[ -r -f "/file.png" ]]

Question

I was writing an if statement which checked if a file is readable and exists by doing the following:

if [[ -r "$upFN" && -f "$upFN" ]]; then
....
fi

Then I thought, surly you can make this smaller, something maybe like this:

if [[ -r -f "$upFN" ]]; then
....
fi

But this doesn't work, it returns errors:

./ftp.sh: line 72: syntax error in conditional expression
./ftp.sh: line 72: syntax error near `"$upFN"'
./ftp.sh: line 72: `if [[ -r -f "$upFN" ]]; then'

Answer 1

AFAICT, there is no way to combine them further. As a portability note, [[ expr ]] is less portable than [ expr ] or test expr. The C-style && and || are only included in bash so you might want to consider using the POSIX syntax of -a for and and -o for or. Personally, I prefer using test expr since it is very explicit. Many shells (bash included) include a builtin for it so you do not have to worry about process creation overhead.

In any case, I would rewrite your test as:

if test -r "$upFN" -a -f "$upFN"
then
  ...
fi

That syntax will work in traditional Bourne shell, Korn shell, and Bash. You can use the [ syntax portably just as well.