Sponsored Content
Top Forums Shell Programming and Scripting Perl: Opening a filehandle but not getting anything back from it Post 302224046 by buffoonix on Tuesday 12th of August 2008 05:50:51 AM
Old 08-12-2008
Hi Smiling Dragon,

glad you could fix that.

Because my eyes got too distracted I copied and pasted your buggy and fixed versions of the second sub and made a diff
Code:
$ diff bla?
9c9
<                         open(SYSMAN, "$sysman|") || return;
---
>                         open(SYSMAN, "$sysman|");
15c15
<                         $sysmanhandle=shift @sysmanhandles;
---
>                         my $sysmanhandle=shift @sysmanhandles;
23d22
<                         close($sysmanhandle);
24a24
>                         close($sysmanhandle);

I think the removal of return on a failed open didn't make the difference
(though I would assume it to be better style after all if you couldn't reconcile with a die on that condition).
However, what I think made the difference was the explicit lexical redeclaration of $sysmanhandle.

I also would have advised to set the autoflush before the reading loop by squeezing in a
Code:
$|++;

hadn't you come up with the solution.

Sorry, for ill-advising you on presumed redundancy of quotes.
Even if I were right it is always better to be explicit.
I just was thinking about a talk I once attended at a Perl conference or workshop held by
Mark Jason Dominus (author of Higher Order Perl)
where he ranted about cave men dwellers' useless quoting voodoo.
He there brought onto my radar the wonderful Deparse module
to check what Perl really makes out of your expressions.
Have a look at
Code:
$ perldoc B::Deparse

in case you haven't come about it yet.
Quote:
I'll give that a try but I suspect I'll hit trouble as I'm obliged to use a fairly old perl (old system that's not to be fiddled with more than absolutely necessary).
The lexical vars as valid file handles to an open call became available as of Perl 5.6.0
if I remember correctly.
If your Perl is that old or even older then you should really consider an update Smilie
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Opening Perl

I have gone to /usr/bin/ and click on perl but notting happens.also notting happens when i click on c/c++ or any other program whats wrong ? (2 Replies)
Discussion started by: perleo
2 Replies

2. Shell Programming and Scripting

perl: howto print to screen & filehandle

Hello, I need to print messages both to screen and to file handle in perl , like tee does in unix . Any suggestions ? Thanks (2 Replies)
Discussion started by: Alalush
2 Replies

3. Shell Programming and Scripting

Opening Files and checking contents in Perl

Hi All, I need some expert help in performing the following in Perl. I have a code below but it doesn;t seem to work. Can any expert give me some advice? Below are the requirements 1) Open numerous files assigned to an array @FILES. Note that the files are always named with the term... (7 Replies)
Discussion started by: Raynon
7 Replies

4. Shell Programming and Scripting

Opening Mulitple files using For loop in Perl

Hi All, I have a total of ten file to open in the Perl script and i am using a for loop to open each file and capture some strings inside each file. Unfortunately, i encounter the below syntax error. I think there should be something wrong with this term reports_${counting}_${_}.txt but i do... (4 Replies)
Discussion started by: Raynon
4 Replies

5. Shell Programming and Scripting

How to call a shell script from a perl module which uses Filehandle to login

Hi Guru's, Pardon me for the breach of rules..... I have very little knowledge about Shell Programming and Scripting hope you guys help me out of this troble I have very little time hence could not find the right way to direct my queries. coming to the problem I need to call a... (2 Replies)
Discussion started by: saikrishna_tung
2 Replies

6. Shell Programming and Scripting

Perl-opening a file then copying files

Good morning guys!! Im still practicing with Perl and now Im trying to open a file, and copy its contents to another file. Them I want to remeove the information out of the orginal file after it is copied over. The flow should be messages-->messages1-->messages2. Kind of like a log... (1 Reply)
Discussion started by: bigben1220
1 Replies

7. Programming

Error:readline() on closed filehandle Perl

Hi, i have run the below perl code and i am getting an error Error:readline() on closed filehandle OR at run.pl line 31. CODE: =========================================== open OR,$ARGV; while (<OR>) { # find the batch date next if length $_ < 3; # BLANK LINE # last if $. > 120; #... (3 Replies)
Discussion started by: pspriyanka
3 Replies

8. UNIX for Dummies Questions & Answers

Opening a file in perl

Hi I need to open a file if a condition(for example a if a regular expression) is met. How do i do this ? open (file) if (some regex)..... (3 Replies)
Discussion started by: manutd
3 Replies

9. Shell Programming and Scripting

perl FileHandle Closure during after unlock

Hi we have one function which is used to append data the file in exclusive lock mode in aperl script. This script is executed by multiple threads at the same time. accessing the same file.this script runs throught the day. sometimes the file2.txt size is getting reduced. for eg from 10 M... (1 Reply)
Discussion started by: Shahul
1 Replies

10. Shell Programming and Scripting

Printing a message in file without opening it in perl

Hello friends, i have a perl script as below ... for (0 ..$#values) { ##want to print some message here in Report.txt file print `find /abc/xyz/pqr/$values" -type f -ls` >> Report.txt } I am able to get output of print `find /abc/xyz/pqr/$values" -type f -ls` >> Report.txt in... (2 Replies)
Discussion started by: harpal singh
2 Replies
SHELL-QUOTE(1)						User Contributed Perl Documentation					    SHELL-QUOTE(1)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.16.3 2010-06-11 SHELL-QUOTE(1)
All times are GMT -4. The time now is 10:03 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy