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

Hi, I am new to Perl, learning how to parse a linux log file. So, I grep sth from the log, serving as input to m parse script and print the result to a proper format.

[linux host] $ grep "Something" sample.log | perl myParser.pl 

my $line;
foreach $line (<>) {
...
}

[download]

This works fine, but I would like to supply more parameter to my perl script to determine the format style, eg. 

$ grep "Something" sample.log | perl myParser.pl VERTICAL

[download]
will print the result vertically, 
$ grep "Something" sample.log | perl myParser.pl COLUMN

[download]
will print the result in columnized format.

I tried to capture it by $ARGV[0], $ARGV1, but still failed. Please kindly help

More, i did a simple test 

#!/usr/bin/perl
use strict;
my $param0 = $ARGV[0];
my $line;

print "\nFirst Arguement is : $param0";

foreach $line (<>) {
...
}

[download]

$ grep "Name=" sample.log | perl SimpleTest.pl VERTICAL 

Can't open VERTICAL: No such file or directory at SimpleTest.pl line 1
+1.
First Arguement is : VERTICAL

[download]

Then , it just stopped and not execute the foreach loop

Replies are listed 'Best First'.
Re: More Arguments
by Athanasius (Archbishop) on Sep 05, 2015 at 04:31 UTC

    Hello joaming,

    To get the syntax right, you’ll need to study perlop#I/O Operators:

    The null filehandle <> is special: it can be used to emulate the behavior of sed and awk, .... Input from <> comes either from standard input, or from each file listed on the command line. Here's how it works: the first time <> is evaluated, the @ARGV array is checked, and if it is empty, $ARGV[0] is set to "-", which when opened gives you standard input....

    By trial and error, I found the following (on Windows), which seems to do what you’re looking for:

    14:17 >echo Hello| perl -wE "$x = <>; chomp $x; $y = $ARGV[0]; say qq[
+>$x $y<];" - world
>Hello world<

14:17 >

    [download]

    The call to <> finds - as the first argument on the command line and so reads from standard input, which is Hello\n. After this, @ARGV is apparently reset. I haven’t found that behaviour documented (yet).

    Anyway, hope that helps,

    Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

[reply]
[d/l]
[select]
      Thank you. I still have a long road to walk on Perl, lol
[reply]
Re: More Arguments
by choroba (Cardinal) on Sep 05, 2015 at 07:18 UTC
    Don't use the bare diamond <> if you want to handle arguments yourself and read from the standard input. Use <STDIN> instead: 
    echo input | perl -we 'print "ARGS: @ARGV\n"; print while <STDIN>' fil
+e.txt arg2

    [download]
    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]
[d/l]
[select]
Re: More Arguments
by stevieb (Canon) on Sep 05, 2015 at 03:37 UTC

    Hey, joaming, welcome to the Monastery.

    Could you please provide some of your input data, expected output and a bit more of your code? This will help us determine where we can improve on what you've already got.

    -stevieb

[reply]
      I am sorry I didn't address what I encountered at the first place accurately. Now I updated with a SimpleTest.pl, I expect the code continue to run and enter the foreach loop, but it didn't.
[reply]
Re: More Arguments
by parv (Parson) on Sep 05, 2015 at 03:35 UTC

    Show your code where you try to use @ARGV & fail.

[reply]
[d/l]
Re: More Arguments
by QuillMeantTen (Friar) on Sep 06, 2015 at 14:12 UTC

    You can keep the code you wrote and just use xargs that way you will call your script multiple times with just one argument
    Update: oops my bad I misread what you wrote, please disregard

[reply]

Back to Seekers of Perl Wisdom