Re: help with combining expressions in an if statement

[Jim]

Chris F.A. Johnson wrote:
> On Sat, 1 Jan 2005, Jim wrote:
>
> > Hi,
> >
> > I am new to bash and am looking for some help. Specifically, I would 
> > like to ensure the user supplies two arguments to the shell script - 
> > month and year. How should I combine multiple expressions in an if 
> > statement?
> >
> >
> > So far I have the following script :
> >
> > month=$1
> > year=$2
> >
> > if [ -z$month -o -z$year ]; then
> > echo "Usage: $0 month year";
> > echo "example: date.sh 01 2005";
> > exit 1
> > fi
> >
> > In other words I want to say if A is true OR B is true then echo output.
>
>
>               The number of arguments is in the variable $#, so you can 
> check
>               that:
>
> [ $# -ne 2 ] && {
>             echo "Usage: $0 month year"
>             echo "example: date.sh 01 2005"
> }
>
>               Or you can test each variable:
>
> [ -n "$1" ] && [ -n "$2" ] || {
>             echo "Usage: $0 month year"
>             echo "example: date.sh 01 2005"
> }
Thanks Chris.

As a matter of interest what was wrong with 'if [ -z$month -o -z$year ]' ?

-z means string has a length of zero
-o is the "or" operator which can be used to combine two expressions

If I wanted to combine two expressions in an 'if' test, how would I do it?

Jim