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Shell Corner: Littera Delenda Est (Part Two)
Ed Schaefer
In this month's Shell Corner, Royce Williams provides part two of his attack on removing unusual characters in filenames.
Wed, 30 May 2007
Shell Corner: Littera Delenda Est
Ed Schaefer
Reader Royce Williams describes his experiences removing files with tricky characters in their filenames in part one of his article.
Sun, 29 Apr 2007
Test Your Knowledge of Regular Expressions and Shell Basics
Emmett Dulaney
Emmett lets you test your knowledge of regular expressions and shell basics.
Fri, 30 Mar 2007
Epoch to UTC Time Conversion
Ed Schaefer
In this column, Bob Orlando presents an Epoch script that is portable among Unix variants.
Tue, 27 Feb 2007
Parsing Web Form Input in CGI Shell Scripts
This month's Shell Corner is for CGI programmers. Chris Johnson provides the Bash (version 2.0 or greater) shell function parse_query for processing web forms.
Sat, 30 Dec 2006
Shell Corner: The dspl (Display List) Korn Shell Script
Ed Schaefer
This month, Gary Powell provides us with filter dspl, which allows you to display the current directory's contents in various columnar formats.
Wed, 29 Nov 2006
Shell Corner: Logeasy and Logez — Handling Log Files
Ed Schaefer, Michael Wang
I'm always intrigued by problems solved by using recursion — especially in the shell. This month, Julie and Michael Wang use recursion in their logez function — one of their two methods for handling log files.
Mon, 18 Sep 2006
Shell Corner: Bash Dynamically Loadable Built-in Commands
Ed Schaefer, Chris F.A. Johnson
Bash shell programmers can improve the efficiency of their scripts by using the shell's dynamically loadable built-in commands. This month, Chris F.A. Johnson shows us how to use them.
Tue, 6 Jun 2006
Shell Corner: Graphing Perl's Regular Expressions
Ed Schaefer, Steve Oualline
Perl's regular expressions are cryptic, difficult to write, and impossible to understand. However, when graphed, the strings suddenly turn into something simple and fairly easy to understand. This month, Steve Oualline presents a Perl program that takes regular expressions and not only graphs their logic but their execution as well. It is all part of his book, Wicked Cool Perl Scripts.
Tue, 18 Apr 2006
Shell Corner: Safely Sharing Screen Sessions with sudo
Ed Schaefer, Rod Knowlton
Knowlton describes a couple of tempting but insecure methods for easing the work of sharing screen sessions, reveals their faults, and then presents a set of scripts that act together to provide a safe, easy to use alternative.
Wed, 15 Mar 2006
Shell Corner: PS-n-Grep — The Steroid Version
Ed Schaefer, Bob Orlando
How many of us check the Unix process table using the ps command and pipe it to grep? This month, Bob Orlando presents Perl and awk scripts that add intelligence to this process.
Tue, 7 Feb 2006
Book Review: Write Portable Code
Ed Schaefer
Ever notice how people who are really passionate about a topic will tell you everything they know, think they know, or even suspect? I think author Brian Hook is that way concerning cross-platform software development. Hook has an opinion on everything from source code control to operating systems to internationalization.
Tue, 10 Jan 2006
Shell Corner: Some Useful XEmacs Customizations
Ed Schaefer
In the past, any Unix system that did not have the vi editor was considered neutered. While many users still believe that, my opinion is the best Unix text editor is the one you know, and, today, many people do know Emacs. Scuttlebutt has it that even Bill Joy — the creator of vi — uses Emacs. With Emacs users in mind, Tom Benton presents some useful XEmacs customizations.
Tue, 6 Dec 2005
John & Ed's Miscellaneous "Split" Tips
Ed Schaefer, John Spurgeon
The theme of this column revolves around splitting files. The first tip finds duplicate files in a file system or directory structure. Once we can identify duplicate files, the next two tips eliminate duplicate records in a file and sort separate blocks of text in a file using the Unix split and csplit commands respectively.
Tue, 8 Nov 2005
Shell Corner: Reading Function and Cursor Keys in a Shell Script
Ed Schaefer, Chris F.A. Johnson
This month, Chris F.A. Johnson presents Reading Function and Cursor Keys in a Shell Script.
Tue, 1 Nov 2005
Shell Corner: c2ms script
Ed Schaefer, Rich Teer
Rich Teer is the author Solaris Systems Programming, and at the end of the book's preface, Rich mentions his shell-scripting solution for including source code in groff documents. I asked him to share it with us.
Tue, 4 Oct 2005
Book Review: Shell Scripting Recipes: A Problem-Solution Approach
Ed Schaefer
If you like shell scripting books with a ton of examples, like Taylor's Wicked Cool Shell Scripts or Michael's Mastering Shell Scripting, you are going to love Chris F. A. Johnson's Shell Scripting Recipes. The author provides more than just a glimpse at shell scripting; in 108 example scripts, Johnson demonstrates what a competent, experienced shell programmer can do.
Tue, 6 Sep 2005
Shell Corner: Date-Related Shell Functions
Ed Schaefer, Michael Wang, Julie Wang
This month, Julie Wang and Michael Wang weigh in with five date-related shell functions based on the unix cal calendar command.
Tue, 6 Sep 2005
Shell Corner: Verifying Backups with cpverify
Ed Schaefer
This month, Dawid Michalczyk validates backups with his bash script cpverify. The script verifies that the object copied is an exact duplicate of the original.
Tue, 2 Aug 2005
Shell Corner: Mouse Reporting in a Shell Script
Chris F.A. Johnson, Ed Schaefer
This month, Chris F.A. Johnson presents "Mouse Reporting in a Shell Script", which senses mouse clicks in xterm-type terminals under Linux, FreeBSD, and NetBSD.
Tue, 5 Jul 2005
John and Ed's Misc Shell Tips: June 2005
Ed Schaefer, John Spurgeon
This installment of miscellaneous Unix tips contains:
* Using tab characters in a Unix here document
* Obtaining version information from a "C" binary
* Using dummy columns to retain relative sort order
Mon, 20 Jun 2005
Shell Corner: DVD-RAM Daily Backup
Ed Schaefer
This month, Louis Poehlitz shares a Perl script, daily-back, which he uses to back up his home network to DVD.
Tue, 7 Jun 2005
Book Review: Classic Shell Scripting
Peter Salus
If you program on a Unix box or a Linux box, you use the shell. It doesn't matter whether it's sh, csh, ksh, bash, or... You use the shell. And, in all likelihood, if you use the shell, you use scripts.
Robbins and Beebe have produced a book that is really good in a variety of ways: it is well-written; it is well-organized; it is full of worthwhile examples and instances; and the code is lucid and clear.
Wed, 25 May 2005
Shell Corner: Expire script
Daniel Singer, Ed Schaefer
This month, Daniel Singer presents Korn Shell 93 script "Expire". This script automatically deletes individual files that have timed out.
Tue, 10 May 2005
Shell Corner: biggest.sh script Correction
Ed Schaefer
We apologize for any inconvenience if you downloaded the biggest.sh script on April 5. The author fixed the bug and the corrected code is available here.
If you have other questions about the script, please email me at: rendsley@cmp.com.
Wed, 6 Apr 2005
Shell Corner: Finding Large Files with biggest.sh
Ed Schaefer
When I was reviewing Bob Orlando's biggest.sh submission, I asked him what he meant by the term "hernia file". His reply was that a "hernia file means BIG ... big enough to give you one if you tried picking it up, programmatically speaking". His biggest.sh script will find those large files.
Tue, 5 Apr 2005
Shell Corner: Finding Abusive Users with netstat
Ed Schaefer
This month, Todd Neal explains (in bash script netstat.ss) how the netstat command can identify abusive users who are accessing your server from the Internet.
Tue, 1 Mar 2005
Shell Corner: Disk Space Checking with SNMP
Ed Schaefer
diskchecker.sh
by Marc Skinner
This bash script — diskchecker.sh — is an SNMP poller that polls the SNMP OID of the disk partitions defined in the snmpd.conf file on Linux boxes. It polls the disks of hosts defined in the diskchecker.conf file. You can specify the drive and the minimum percentage you want free. Once the percentage is exceeded (e.g., a partition is set for 25% and suddenly only 20% of the partition is free), an email is generated.
Wed, 2 Feb 2005
Shell Corner: Zsh Suite of "keeper" Functions
Ed Schaefer
One of the newer Unix shell is the Z Shell. If you're not familiar with Zsh, it resembles ksh, but has many enhancements; it's the ksh on steroids. This month, Bart Schaefer introduces his Zsh suite of "keeper" functions.
Tue, 18 Jan 2005
John & Ed's Miscellaneous Unix Tips: December 2004
Ed Schaefer, John Spurgeon
Unixreview.com's monthly Shell Corner occasionally publishes a miscellaneous tips column. Readers with scripts too short for a full column have submitted a variety of scripts that we've collected here.
Mon, 29 Nov 2004
Shell Corner: "context" script
Ed Schaefer
In my opinion, Heiner Steven's SHELLdorado is one of the best Unix shell scripting Web sites around. The "context" script he shares this month finds a line matching a search pattern and also shows a variable number of lines before and after the match.
Mon, 29 Nov 2004
Book Review: Unix Shells by Example
Ed Schaefer
When you're a novice, don't you hate it when you're struggling with a shell programming problem and someone advises you to "read the MAN pages"? If you're of the opinion the MAN pages are written by experts for experts rather than for beginners, then Ellie Quigley's Unix Shells by Example may be just what you need.
Sat, 30 Oct 2004
Shell Corner: Introducing rcut
Ed Schaefer
The cut command is one of the “arrows” in the shell programmer’s “quiver”. This month, Anton Gorshkov presents bash shell script rcut that performs an anti-cut operation. Rather than including columns, rcut excludes them.
Sat, 30 Oct 2004
Shell Corner: Generating Server Statistics over the Web Using ksh and html
This month, Jorge Torralba submits a ksh script that calculates system health information and creates an html-formatted file for display via the Web.
Wed, 29 Sep 2004
Shell Corner: Managing Background Commands in Shell Scripts
Ed Schaefer
This month, Rainer Raab discusses how to manage multiple background jobs in Korn shell scripts. After a short job control tutorial, he presents his job_monitor_status shell function that alerts the calling script when all background jobs have completed successfully or failed.
Mon, 30 Aug 2004
Shell Corner: analyze-postings
Ed Schaefer
As an instructor for the University of Phoenix Online, I not only work with Netnews groups for my personal interests, but professionally, too. While it’s not hard to find a Netnews reader (most email programs seem to include NNTP compatibility nowadays), it’s not very easy to do any sort of analysis of news postings, which is exactly what I need to do for my classes.
I need to be able to calculate two things: total number of postings in a given period of time, and number of days during that period that there were postings. For example, if we talked about the first week of September, that’s a 7-day period, during which time a given student could post an arbitrary number of articles on any of 0-7 days.
Fri, 30 Jul 2004
Shell Corner: POP3 mail filtering and retrieval with bash
Ed Schaefer
This month, Chris F.A. Johnson presents Bash script mfilter, which retrieves and deletes email from a POP3 mail server. Chris also presents a short tutorial on communicating with a POP3 server.
Tue, 29 Jun 2004
Book Review: Linux Shell Scripting with Bash
Ed Schaefer
Linux Shell Scripting with Bash
A comprehensive guide and reference for Linux users and administrators
by Ken O. Burtch
SAMS Publishing, 2004
ISBN: 0672326426
412 pages
Tue, 29 Jun 2004
Book Review: The Shellcoder's Handbook
At the same time as I was reading this book, my daughter was reading one on Pocahontas. It wasn’t until I hit the half-way mark in mine that the parallels hit me. In the book she was reading, the Indian chief kept trying to convince John Smith to give him rifles and Smith repeatedly agreed to do so but came up with one excuse after another about why it didn’t happen. Smith didn’t want to come right out and say it, but he needed the rifles for his protection and feared what would happen if the Native Americans got ahold of them. This book is the rifle that you want by your side. At the same time, it is the rifle that you hope your friends, users, and enemies never find.
The Shellcoder’s Handbook is far from the first book to talk about holes and weaknesses in applications and operating systems; it is just simply the best. Randomly pick a handful of pages from this book, and you’ll find more information in those pages that you’ll find in most other security books. Without exaggeration, the 24 chapters of this book are crammed with concise, detailed information that will make your head spin.
Sun, 30 May 2004
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Sys Admin and The Perl Journal CD-ROM version 11.0
Version 11.0 delivers every issue of Sys Admin from 1992 through 2005 and every issue of The Perl Journal from 1996-2002 in one convenient CD-ROM!
Order now!
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