UNIX for Beginners Questions & Answers

Might I suggest that you use double quotes wrapped round the arguments too. If $1 is null, then the test becomes invalid and you may get unexpected errors. You can count the arguments as suggested above and use tests such as:-

Code:

if [ -z "$1" ]
then
    echo "First argument is null"
fi

Mixing variable types and operators is usually a bad idea. You need to ensure you compare numbers with numbers using numeric operators and strings with strings with string operators. You can compare numbers using string operators or compare strings using numeric operators, but the results can be unexpected. For instance if you compare 1234 with 321, in a string comparison, 321 is considered larger because it starts with a 3.

You should not really quote numerics.


I hope that this helps,
Robin