Integer comparison in bash

Question

I need to implement something like:

if [ $i -ne $hosts_count - 1] ; then cmd="$cmd;" fi

But I get

./installer.sh: line 124: [: missing `]'

What I am doing wrong?

pepoluan · Accepted Answer · 2011-03-10 11:12:15Z

The command [ can't handle arithmetics inside its test. Change it to:

if [ $i -ne $((hosts_count-1)) ]; then

Edit: what @cebewee wrote is also true; you must put a space in front of the closing ]. But, just doing that will result in yet another error: extra argument '-'

Ignacio Vazquez-Abrams · Accepted Answer · 2011-03-10 11:13:28Z

4

The ] must be a separate argument to [.

You're assuming you can do math in [.

if [ $i -ne $(($hosts_count - 1)) ] ; then

answered Mar 10, 2011 at 11:13

Ignacio Vazquez-Abrams

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2 Comments

lstipakov Over a year ago

Thanks, but why I need to use double [[ ? @pepoluan answer also works, without double [[.

Ignacio Vazquez-Abrams Over a year ago

Well, you don't need to, but [[ will let you have unquoted empty variables without causing problems.

Mark Edgar · Accepted Answer · 2011-03-10 15:18:14Z

In bash, you can avoid both [ ] and [[ ]] by using (( )) for purely arithmetic conditions:

if (( i != hosts_count - 1 )); then cmd="$cmd" fi

Lars Noschinski · Accepted Answer · 2011-03-10 11:12:10Z

The closing ] needs to be preceded by a space, i.e. write

if [ $i -ne $hosts_count - 1 ] ; then cmd="$cmd;" fi

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