echo    "Your   name    is  "$1

fi

If you execute mypgm1, as follows:

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matthew@seymour:~$ bash mypgm1

you get the following output:

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Name not provided

However, if you execute mypgm1 as follows:

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matthew@seymour:~$ bash mypgm1 Sandra

you get this output:

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Your name is Sandra

The shell program mypgm1 also illustrates another aspect of shell
programming: the built-in variables provided to the shell by the Linux kernel.
In mypgm1, the built-in variable $# provides the number of positional
parameters passed to the shell program. You learn more about working with
built-in variables in the next major section of this chapter.

Using Positional Parameters to Access and Retrieve

Variables from the Command Line

Using positional parameters in scripts can be helpful if you need to use
command lines with piped commands requiring complex arguments. Shell
programs containing positional parameters can be even more convenient if the
commands are infrequently used. For example, if you use your Ubuntu system
with an attached voice modem as an answering machine, you can write a
script to issue a command that retrieves and plays the voice messages. The
following lines convert a saved sound file (in .rmd or voice-phone format)
and pipe the result to your system’s audio device:

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#!/bin/sh

play voice message in /var/spool/voice/incoming

rmdtopvf /var/spool/voice/incoming/$1 | pvfspeed -s 8000 | \
pvftobasic >/dev/audio