bash: conditional binary operator expected when checking if a file is readable?

Question

I have this code that works perfectly on one Macbook but doesn't work on another Linux machine in bash. When run in the Linux machine, I get an error "conditional binary operator expected" "syntax error near ${testfile}'" when trying to check if the file in the variable is readable or a file.

for file in "${@:2}"
do
 if [[ ! -rf ${file} ]]

when I make it [ ! -rf "$file" ] I get: [: -rf: unary operator expected

-rf does indeed seem to work on my MacBook but I have no idea what it's supposed to do, and I get the same error when I try it on a random old Debian box where presumably I have an older version of Bash. What's the actual purpose of this script? — tripleee
– tripleee, Commented Jan 18, 2018 at 8:19
I'm guessing maybe it's a way to write [[ ! -r $file -a ! -f $file ]] which of course then should be portable back to Bash v2 and possibly beyond. — tripleee
– tripleee, Commented Jan 18, 2018 at 8:21
My bad, that should be [[ ! -r $file && ! -f $file ]] but I'm still guessing here. Can you confirm that you are trying to check that the file exists and is a regular file and is readable? — tripleee
– tripleee, Commented Jan 18, 2018 at 9:18

sahaquiel · Accepted Answer · 2018-01-18 08:29:24Z

1

[[ ! -r "${file}" && ! -f "${file}" ]]

or:

[ ! -r "${file}" -a ! -f "${file}" ]

answered Jan 18, 2018 at 8:29

sahaquiel

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3 Comments

novel Over a year ago

Is there a difference between using -a and not using -a?

sahaquiel Over a year ago

@novel you can't use -a with [[, you also can't use && with [. These solutions are equal.

tripleee Over a year ago

Well except that more broadly [[ is in many ways different than [, and often more convenient (e.g. in that it's less demanding when it comes to quoting its arguments).

LMC · Accepted Answer · 2018-01-18 18:56:13Z

1

Just using the -r test will work

if [[ ! -r ${file} ]]

answered Jan 18, 2018 at 18:56

LMC

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