How to do a logical OR operation in shell scripting

bash unix if-statement sh

Strawberry · Nov 6, 2010 · Viewed 984.7k times · Source

I am trying to do a simple condition check, but it doesn't seem to work.

If $# is equal to 0 or is greater than 1 then say hello.

I have tried the following syntax with no success:

if [ "$#" == 0 -o "$#" > 1 ] ; then
 echo "hello"
fi

if [ "$#" == 0 ] || [ "$#" > 1 ] ; then
 echo "hello"
fi

Answer

This should work:

#!/bin/bash

if [ "$#" -eq 0 ] || [ "$#" -gt 1 ] ; then
    echo "hello"
fi

I'm not sure if this is different in other shells but if you wish to use <, >, you need to put them inside double parenthesis like so:

if (("$#" > 1))
 ...