[Chicago-talk] Q on '-n'

[Jay Strauss]

what's the -o flag?  I don't see it under perl -h

Jay
----- Original Message ----- 
From: "Mike Pastore" <mike at oobak.org>
To: "Chicago.pm chatter" <chicago-talk at mail.pm.org>
Sent: Tuesday, September 16, 2003 4:53 AM
Subject: Re: [Chicago-talk] Q on '-n'


> Hi Walter,
> 
> Certainly, you are close! But I might offer some suggestions. To answer
> your last email first, it is easy enough to check @ARGV in your BEGIN
> statement:
> 
>     BEGIN
>     {
>         die "usage: $0 -o <output> <input 1> <input 2> ... <input n>\n" 
>             unless @ARGV > 2;
>         ...
> 
> Or perhaps check after you trim out your option. I might also recommend
> the -s switch in this case, as in the following:
> 
>     #!/usr/bin/perl -n -s
> 
>     BEGIN
>     {
>         die "usage: ... \n" unless @ARGV and defined $o;
> 
>         open(TEMP, ">>$o") 
>             or die "Unable to open '$o' for writing: $!\n";
>     }
> 
>     print TEMP; 
> 
> There is no need to close any filehandles. Your data is coming from
> STDIN. You may close TEMP in an END block if you wish, but it is
> unnecessary.
> 
> Regarding style (and your future goal of letting the user specify a
> directory), consider letting user's shell do all the hard work. For
> example,
> 
>    $ perl -pe';' file1 file2 >> file3
>    $ perl -ne'print if /foo/' dir1/* > file3
> 
> Of course, it all depends on the program you're writing. This may not be
> a feasible solution to your problem. But I thought I'd mention it,
> because it might save you time! When writing little scripts like this I
> prefer to let UNIX do all the grunt work of listing directories and
> pushing data around, instead of opening file handles left and right.
> Also, if you use STDOUT and STDERR it gives the user freedom to act on
> the output as s/he sees fit. FWIW.
> 
> --
> Mike Pastore
> mike at oobak.org
> 
> ----- Original message -----
> From: "Walter Torres" <walter at torres.ws>
> To: "Chicago.pm chatter" <chicago-talk at mail.pm.org>
> Date: Tue, 16 Sep 2003 02:14:39 -0500
> Subject: [Chicago-talk] Q on '-n'
> 
> I'm trying to figure out how to utilize '-n' best.
> 
> I have a cmd line...
> 
>    myScript.pl file_1.txt file_2.txt -o result.out
> 
> I want to cycle through all file[s] given by the cmd line (if it's a
> path,
> all the files in that dir, but that's for later) and spit the results
> (whatever it may be) into the file given via the '-o' parameter.
> 
> My test script (see below)
> 
> Is this the best way to accomplish this?
> 
> Thanks for your help.
> 
> Walter
> 
> 
> ==================================================
> 
> #!/usr/local/bin/perl -n
> 
> BEGIN
> {
>    # place entire cmd line into single scalar
>    $arg = join ' ', @ARGV;
> 
>    # split off the inbound file(s) and the result file
>    ($arg, $outFile) = split '-o', $arg;
> 
>    # rebuilt the cmd line
>    @ARGV = split ' ', $arg;
> 
>    # Open given tmp file
>    open( TEMP, ">>$outFile")
> or die "No Way! \n$!\n$outFile\n";
> }
> 
> # loop begins here
> print TEMP "$ARGV: $.\n";
> 
> # clode the file when we are done with it
> close ARGV if eof;
> 
> # eof
> 
> 
> _______________________________________________
> Chicago-talk mailing list
> Chicago-talk at mail.pm.org
> http://mail.pm.org/mailman/listinfo/chicago-talk
> _______________________________________________
> Chicago-talk mailing list
> Chicago-talk at mail.pm.org
> http://mail.pm.org/mailman/listinfo/chicago-talk
> 
>