Bash shell scripting question

mehesque · 07-15-2004, 09:31 AM

This just deals with easy if statements, but I'm not too knowledgible about Bash's quirks.

I wrote a script that only needs one argument passed into it. However, I'm not sure how to output instructions about how to use the script if no argument is passed in.

Basically, my whole script consists of a lot of if's. But, problem number 2 arises if the proper if isn't found. I tried to put an else at the end, but that doesn't work because it is a standalone else outside of an if statment.

My solution is this, but how do I implement it. How would have an outside if that accepts any arguement but blank? Then have a second if to accept nothing.

Thanks for your time.

Dark_Helmet · 07-15-2004, 09:47 AM

How about this:

Code:

#!/bin/bash

# Function to display usage. Everything between "cat << EOF" and "EOF" is
# displayed on the terminal.
function display_usage()
{
  cat << EOF
Basic Usage:
  $0 <argument>

<argument> is required, and causes action foo.
EOF
}

# Start of the main script. $# is a psecial variable that contains the number of
# arguments on the command line.
if [ $# -eq 0 ] ; then
  echo "Not enough arguments on command line. Displaying usage..."
  display_usage

  # This will preven the script from continuing execution since the
  # requirement of one or more arguments was not met.
  exit 1
fi

# If the script reaches this point, there are 1 or more arguments on the command line.

mehesque · 07-15-2004, 10:54 AM

Yeah, that will work, thanks a lot!!!