[: -gt: unary operator expected

Question

I don't write a lot of Bash, so I'm a bit stumped as to how to fix this. I need to check whether a value returned from a command is greater than x. When it runs though I get [: -gt: unary operator expected which I'm unable to fix.

Here is my script,

#!/bin/sh
ERROR=0
PHPCPDLevel=100

# PHPCPD
echo "PHP CopyPaste Detection (Limit is at least ${PHPCPDLevel}%"
PHPCPD="phpcpd ."
if [[ `echo $PHPCPD | grep "%" | cut -d'.' -f1` -gt "$PHPCPDLevel" ]]
  then
    echo $PHPCPD
    ERROR=1
  else
    echo "... -> Only `echo $PHPCPD | grep "%" | cut -d'.' -f1`%"
fi

echo "Finished!"
exit $ERROR

Update: I think I've done it:

#!/bin/sh
ERROR=0
PHPCPDLevel=25

# PHPCPD
echo "PHP CopyPaste Detection (Limit is at most ${PHPCPDLevel}%)"
PHPCPD="phpcpd ."
PERCENTAGE=$($PHPCPD | grep "%" | cut -d'.' -f1)
if [ ${PERCENTAGE} -gt ${PHPCPDLevel} ]
  then
    echo $PHPCPD
    ERROR=1
  else
    echo "Only $PERCENTAGE%"
fi

exit $ERROR

It is good to perform any operation first and store result in variable then compare. — Jayesh Bhoi, Jul 25 '14 at 10:23
I don't think there is a space, when I run it, it seems fine. — James, Jul 25 '14 at 10:25
`echo $PHPCPD` is not like you run command? Try with `PHPCPD=$( phpcpd . | grep "%" | cut -d'.' -f1)` and compare it like `if [ $PHPCPD -gt "$PHPCPDLevel" ]` — Jayesh Bhoi, Jul 25 '14 at 10:32
Ok, but quote the variables in the expansion, like `if [ "$PERCENTAGE" -gt "$PHPCPDLevel" ]` otherwise the it will fail if the pipeline does not give any output. — user000001, Jul 25 '14 at 10:38
This is weird, my edited script works on my Mac, but when it's running on GitLab it's telling me that 9% is > 99% (I've since changed the level). — James, Jul 25 '14 at 10:41
Are you comparing with the percentage mark `%` inside the variables? — user000001, Jul 25 '14 at 10:42
Nope. https://gist.github.com/jbrooksuk/b36403f6277a94bc4faa — James, Jul 25 '14 at 10:43
And https://gist.github.com/jbrooksuk/b36403f6277a94bc4faa#comment-1269875 is the output from GitLab-CI. — James, Jul 25 '14 at 10:44
The canonical may be *["unary operator expected" error in Bash if condition](https://stackoverflow.com/questions/13617843/)* — Peter Mortensen, Oct 05 '21 at 16:55

score 9 · Accepted Answer · answered Jul 25 '14 at 12:46

Remember that [ is a command. It maybe built into your shell, but it's still a command. It is expecting a particular set of parameters, and will give you an error when it gets something it doesn't understand. In fact, you can replace [ ... ] with test ... if that makes things a bit easier to understand:

For example:

test -gt 34

Will return:

bash: test: -gt: unary operator expected

Hmmm... same error message.

When you get things like this, you should use set -xv and set +xv around the problem area of your shell script. The set -xv will print out the shell command to be executed, and then will show you what the command line looked like after it has been ~~mangled~~ I mean interpolated by the shell.

I suspect that your error is:

if [ ${PERCENTAGE} -gt ${PHPCPDLevel} ]

That ${PERCENTAGE} is a blank value. If you use [[ ... ]] instead of [ ... ] you won't get that error. The [[ ... ]] is parsed a bit differently than [ ... ] because it's a compound command. The shell interpolations are done after the initial command is parsed, so it's a bit more forgiving if you miss a quotation mark or strings contain unexpected characters.

So:

ERROR=0
PHPCPDLevel=25

# PHPCPD
echo "PHP CopyPaste Detection (Limit is at most ${PHPCPDLevel}%)"
export PS4="\$LINENO: "     # Prints out the line number being executed by debug
set -xv                     # Turn on debugging
PHPCPD="phpcpd ."
PERCENTAGE=$($PHPCPD | grep "%" | cut -d'.' -f1)
if [[ ${PERCENTAGE} -gt ${PHPCPDLevel} ]]  # Use [[ ... ]] instead of [ .. ]
then
    echo $PHPCPD
    ERROR=1
else
    echo "Only $PERCENTAGE%"
fi
set +xv                     # Turn off debugging

exit $ERROR

Now, you'll see what the various commands that set environment variables are returning, and possibly see something you didn't quite expect.

score 4 · Answer 2 · answered Jul 25 '14 at 10:24

4

You can't use double brackets [[ ... ]] in sh. Change your sheebang to

#!/bin/bash

or change the syntax to use single brackets [ ... ]. Don't forget to quote the terms inside the expression if you do that.

answered Jul 25 '14 at 10:24

user000001

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I've changed it, but it's still not worked. I'm just trying something slightly different now. – James Jul 25 '14 at 10:28
1

@James Also you do `PHPCPD="phpcpd ."` and then execute `echo $PHPCPD`. Don't you wan't to run the command, like " `phpcpd . | grep ...`? – user000001 Jul 25 '14 at 10:31
@user000001 yes, that was my plan. – James Jul 25 '14 at 10:32
1

Ok, I switched to `#!/bin/bash` and using double brackets to compare `[[ 9 -le 5 ]]` but that's returning true. What? – James Jul 25 '14 at 11:02
2

@James Are you sure? Try `[[ 9 -le 5 ]] && echo true || echo false` on a terminal. I get false. – user000001 Jul 25 '14 at 11:04
1

Yep, absolutely sure. – James Jul 25 '14 at 11:08

[: -gt: unary operator expected

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