How to write if else in one line in shell?

问题:

I would like to write in one line this:

if [$SERVICESTATEID$ -eq 2]; then echo "CRITICAL"; else echo "OK"; fi

So to do a test in my shell I did:

if [2 -eq 3]; then echo "CRITICAL"; else echo "OK"; fi

The result is

-bash: [2: command not found
OK

So it doesn't work.

回答1:

Space -- the final frontier. This works:

if [ $SERVICESTATEID -eq 2 ]; then echo "CRITICAL"; else echo "OK"; fi

Note spaces after [ and before ] -- [ is a command name! And I removed an extra $ at the end of $SERVICESTATEID.

An alternative is to spell out test. Then you don't need the final ], which is what I prefer:

if test $SERVICESTATEID -eq 2; then echo "CRITICAL"; else echo "OK"; fi

回答2:

Write like this, space is required before and after [ and ] in shell

if [ 2 -eq 3 ]; then echo "CRITICAL"; else echo "OK"; fi