Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I'd like to present a descrition of the script I wrote along with the command line syntax and argument list when the program is called without] any filenames or options set. i.e. 
% perl my_program

This program does...
myprogram [option][filename]
          -x does something
          -y does something else

[download]
I'm just learning and I haven't been able to find anything related for reference. Thanks in advance.

Replies are listed 'Best First'.
RE: No arguments or filenames
by DrManhattan (Chaplain) on Aug 07, 2000 at 19:16 UTC

    The command line arguments for your script live in the array @ARGV:

    #!/usr/bin/perl -w

if (!@ARGV)
{
    print STDERR << "SYNTAX";
myprogram [option][filename]
            -x does something
            -y does something else
SYNTAX
    exit 1;
}

    [download]

    Also, take a look at the Getopt::Std module to handle your switch processing.

    -Matt

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Re: No arguments or filenames
by KM (Priest) on Aug 07, 2000 at 19:16 UTC
    You can take a look at Getopt::Long, Getopt::Simple, Getopt::*, etc.. or do something like, or some variant of:

    unless (@ARGV) {
     print qq{I am helpful.};
}

    [download]

    Cheers,
    KM

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(Guildenstern) Re: No arguments or filenames
by Guildenstern (Deacon) on Aug 07, 2000 at 19:16 UTC
    try:
    usage() unless @ARGV;
...
sub usage()
{
 #print out program usage info, flags, etc
 #then exit()
}

    [download]

    This will print the usage info and exit if there are no command line parameters (which are stored in @ARGV)
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Re: No arguments or filenames
by TheOtherGuy (Sexton) on Aug 08, 2000 at 01:00 UTC
    Based on your example, you want to use the GetOpt module. A possible example of what has worked for me in the past, with some default values: 
    use strict;
(my $cmd = $0) =~ s|^.*/||;   # Program name

# ----------------------------------------
# Handle Command Line options
use Getopt::Std;
&getopts ('d:r:H');

my $DATE;   # $opt_d
my $RCFILE; # $opt_r

# --------------------
# Date
if ($Getopt::Std::opt_d)
{
    $DATE = $Getopt::Std::opt_d;
}
else
{
    $DATE = "TODAY";
}

# --------------------
# Resource File
if ($Getopt::Std::opt_r)
{
    $RCFILE   = $Getopt::Std::opt_r;
}
elsif ( defined($ENV{RCFILE}) )
{
    $RCFILE = "$ENV{RCFILE}";
}
else
{
    warn "ERROR: No RC File Specified\n";    
    $Getopt::Std::opt_H = 1;
}

# --------------------
# Help
if ($Getopt::Std::opt_H)
{
    warn "$cmd:\n";
    warn "    (-m) <milestone>\n";
    warn "    (-r) <rcfile>\n";
    warn "    (-H) <Help>\n";
    exit 1;
}

    [download]
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RE: No arguments or filenames
by Anonymous Monk on Aug 07, 2000 at 22:06 UTC
    You can do something like my $usage = qq(Usage text); die $usage if !@ARGV; You could also make usage a sub and call it when @ARGV is empty: You should also check out GetOpt::*
[reply]

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