Wicked Cool Shell Scripts

norburym writes with a review of Wicked Cool Shell Scripts - 101 Scripts for Linux, Mac OS X, and UNIX Systems. "This incredibly fun book (really!), written by Dave Taylor, a veteran UNIX, Solaris and Mac OS X author, is chock full of 101 scripts to customize the UNIX (Bourne) shell." Read on for the rest.

Wicked Cool Shell Scripts - 101 Scripts for Linux, Mac OS X, and UNIX Systems
author	Dave Taylor
pages	368
publisher	No Starch Press
rating	10
reviewer	Mary Norbury-Glaser
ISBN	1593270127
summary	101 Scripts for Linux, Mac OS X, and UNIX Systems

Chapters are divided into an array of topics sure to catch the attention of any UNIX based system user: The Missing Code Library, Improving on User Commands, Creating Utilities, Tweaking Unix, System Administration: Managing Users, System Administration: System Maintenance, Web and Internet Users, Webmaster Hacks, Web and Internet Administration, Internet Server Administration, Mac OS X Scripts, and Shell Script Fun and Games.

In true "cookbook" fashion, each hack is numbered and divided into The Code, How It Works, Running the Script, The Results and Hacking the Script. Throughout, the author clearly describes the syntax and functionality of each script, often with additional notes in How It Works detailing the syntax process and interesting asides. But Hacking the Script is what gives Wicked Cool Shell Scripts true value; where applicable, the author uses this section to describe script modifications to achieve a variety of alternative real world, practical results. This additional section alone easily triples the total number of scripts the reader is exposed to.

This book enables the reader to get "up close and personal" with their UNIX based system and explore the possibilities afforded by becoming intimate with the command line interface. The reader will find themselves easily propelled into the world of scripting, thanks entirely to Dave Taylor's ability to take what some might describe as a fairly dry topic and translate it into a logical and user friendly construct. Just reading through the table of contents is inspiring and intriguing; did you know you could write a script to retrieve movie info from IMDb? or track the value of your stock portfolio? or that you can use a very simple script to check spelling on your web pages?

Sysadmins and webmasters will find this book fundamentally critical to day-to-day operations; there are dozens of invaluable, customizable scripts highlighted in this book to enable professionals to save time and add simple, elegant solutions to annoying issues in their work environment. User account management, rotating log files, cron scripts, web page tweaks, apache passwords, synchronizing via ftp, etc. are all eminently useful and tweakable.

Geeky home users will discover they can use these scripts to work with files and directories, create spell-checking utilities, calculate loan payments, create summary listings of their iTunes libraries, and of course, play games. Many of the sysadmin scripts would also be of interest to the power user: analyzing disk usage, killing processes by name and backing up directories, to name a few. Both types of users will find this book inspiring and truly fun!

One of the secret pleasures of a technical book reviewer is finding those wonky bits of code that suffer from misplaced or missing punctuation, misspelled words and other basic typographic errors inherent in the book publishing process. I randomly selected many of these scripts to try out in the process of doing this review and...dang, haven't found any errata yet. But be sure to check out the errata page on Dave Taylor's web site for any that more astute readers may find (there were none, as of this writing).

Also be sure to take a closer look at Dave's shell script library, which lists additional scripts that didn't make the cut for the book. As convenient as it is to download the entire script library, I would like to stress the value of buying the book, which will provide you with invaluable instruction and guidance in understanding the syntax of the scripts and it also illustrates how making small but significant tweaks can modify the output to match your specific needs.

(A special nod of appreciation to Dave Taylor's Tintin references!)

---

You can purchase Wicked Cool Shell Scripts - 101 Scripts for Linux, Mac OS X, and UNIX Systems from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

What about us Windows users?!

I could use some wicked cool batch files.

Re:What about us Windows users?!

Get a copy of Windows Admin Scripting Little Black Book [amazon.com], or something similar. I got a copy of the first edition at Borders for $5, you may find similar on ebay or half.com.

Re:What about us Windows users?!

this reminds me of when I used to hang out on IRC and set the channel topics to "press ALT-F4 for ops!" Half the channel would drop

Re:What about us Windows users?!

Just use cygwin.

Re:What about us Windows users?!

Somewhere I found a standalone sh.exe that is only 344K and can be run from the command line just like:
C:\> sh.exe myscript.sh

MinGW

The good folks at MinGW.org [mingw.org] make a package called MSYS that has most of the binutils and runs as native apps under windows. I use it a lot, it's really handy when I want to download and open a bzipped tar file on windows.

The latest version of sh.exe is 465k bytes, it sounds like you have an old version. You should upgrade it. :)

Re:What about us Windows users?!

I could use some wicked cool batch files.

Cygwin [cygwin.com] is your friend. For just one example, you can write a script that uses sed to extract information from the filenames of your mp3z and feed the results into id3ed to tack on an ID3 tag. Try doing that with a batch file.

Re:What about us Windows users?!

Exactly. What makes shell scripts so much better on Unix isn't really the shell, it's the flexibility of the programs that come with a Unix.

That's true, but the fallacy is that you're assuming Windows should be scripted in the same fashion as *nix. That's simply not the case. Batch/Command scripting is nice for small bits, and can actually be fairly powerful in an obtuse sort of way, but the real power in automating Windows comes by using the Windows Scripting Host, JScript or VBScript, and all of the ActiveX/COM interfaces into the functionality of the OS and other applications. A classic example is iterating through users. In *nix, you write a shell script to parse through /etc/passwd. In Windows, you write a jscript to instantiate the objects that deal with Active Directory, and iterate through user objects (each of which you can perform actions upon, wherein *nix you'd have to invoke other applications). One approach is not necessarily "better" than the other, but you can't assume that your *nix administration experience will directly translate into Windows administration. You'd laugh if a Windows admin felt the reverse was true. What really gets me is when people complain about Windows not being automation-friendly because they're used to *nix scripting. Yes, you cannot pipe notepad.exe into winword.exe, for example, but Word has a very rich automation interface that you can hook into and use from a simple JScript.

Take the DELETE command. It has trouble deleting multiple files at a time. It can't delete directories. Then look at Unix rm. It's easy to see why batch files are a joke.

What? Try running "help del" from a cmd.exe window some time. Also, look at "help rd". If you want to remove a directory tree, you use the "remove directory" command. "del" deletes files. "rd" deletes directories (and can delete files within directories if you tell it to).

The shell itself is definitely more flexible overall, though. Definitely more scriptable. The Bourne way of doing conditions, loops, pipes and whatnot are definitely more intuitive, more flexible, and carry less baggage than command.com or cmd.exe.

Consider cmd.exe to be the functional equivalent of csh. It's a decent interactive shell, and has some good functionality (especially later versions of cmd.exe in win2k and xp), but you'd have to be nuts to do any extensive scripting with it. Just as you'd pull out bash or perl to do more complex tasks in *nix rather than using csh, you should use WSH in Windows for more complicated tasks.

Re:Is that a recipe for bloat?

While I agree with you that piping the output of one program into another to stack utility upon utility is a great feature of [c|k|ba]sh, I don't think you weren't paying attention to the parent post.

The trick with Windows is that you can do many of these same things, but this power comes from doing it in WSH or VB (or C/C++ or an ASP or whatever language you're comfortable with. I've even done it in Perl.) You use the COM interfaces of the shell object to enumerate through directory trees and files. You can stream each of those files into the COM interface of another program that accepts streams. You can search, you can pipe stuff all over, and you're not limited to a single instance of stdin, stdout and/or stderr.

It's not unlike shell scripting, it's just a different language. Each application is able to expose whatever it feels is most important in whatever fashion it thinks is best. DevStudio, for example, lets the scripting host user get to the workspace, the project, and any of the tools.

The biggest problem I have with it is that stdio is not "guaranteed" to be supported by every application under Windows. stdio is the glue that binds all the UNIX utilities together. That's the beauty of stdio -- as the sole mechanism for I/O for most tools, it became the defacto application interaction interface. Windows doesn't have that: most Windows apps don't offer any automated IO at all. And some of the ones that do seem to have interfaces pasted on after the fact. But the ones that do expose properties and methods via COM are easy to access, and easy to control from anywhere. And using the interfaces tends to remove the ambiguities: in UNIX if you're using 'cut' to parse a phone list but the name field sometimes contains commas, you end up hacking around solutions to make them work. A COM-based solution would provide an interface containing a Name field.

Windows is not alone in this limiation, either. UNIX suffers from a similar problem: how do you meaningfully pipe data to and from an X window, or even to a curses app? Is it consistent between apps? Most apps I am familiar with that offer such features in their applications had to have code added to actively support a meaningful commandline interface to their programs through the use of dozens of command line switches. Without this sort of code, using stdio to parse the output of a curses-based application becomes a tedium of screen scraping.

Don't get me wrong: I have a bevy of UNIX-like command line utilities for Windows, I use Cygwin and bash when I need to (although the file system mapping is worse than I could have imagined), and I will fire up a CMD script long before I think to write it as a VB or C++ program. I'm far more comfortable with the sh-style tools -- I grew up with them.

I'm not saying stdio is better or worse than using the COM interfaces of Windows; I'm just saying it's "different." And you certainly shouldn't be reinventing the wheel to script up utilities in Windows.

Re:What about us Windows users?!

I know where you can get a wicked cool .PIF file... Hold on, I'll email it to you. Look for the subject "Your Details".

Re:What about us Windows users?!

lynx -dump www.infiltrated.net/wtf|\
grep "+-"|\
sed 's/\\//g;s/\// /g;s/\&//;s/-/ /g'|\
awk '{print $2,$3,$4,$5}'|\
sed 's/ //g'

Woo

And here I thought I was done with buying books.

*Bookmarks this page for when I get money*

the best shell script

contains one line:
rm -rf *

Re:the best shell script

rm -rf *

A better idea is to write "rm -rf ~/*", name the script "ls" and put it in your home directory to punish people with "." in $PATH . Now _that's_ teh funnay. :)

Re:the best shell script

rm -rf /

One of the reasons I love unix, is that it will let you shoot yourself in the foot, and it will steady the gun while you take aim at your toe.

sounds cool

i like shell scripting. i dont know why, it just seems more enjoyable than programming big apps in java or c++. maybe its just the size, they are done sooner. i use a script that upon booting writes the new IP on a dynamic IP machine to the httpd.conf file, i thought that was kinda cool. nothign complicated, just necessary.

Re:sounds cool

It's because you have to be creative to solve problems. Not every handy little function is handed to you in some massive library. Sometimes, you have to do some really klugy, ugly things to get it to work. And that's fun.

Usage guide found on page one.

Step 1. Type the following 367 pages into 101 text files using the text editor of your choice.
Step 2. Type 'chmod a+x ./*' and hit enter.

Sounds useful, but what languages are used?

This sounds useful, but what languages are used? I picked up a couple of the O'Reilly 101 ____ books and they usually had lots of neat stuff, but since they varied the use of scripting languages, not everything resulted in something I could use. (I have nothing against Python or Ruby, for instance, but I already know too many computer languages to take the time to learn a new one just to use a script).

Re:Sounds useful, but what languages are used?

Yes but you are missing a big point here.

The programming languages like C, C++, Java etc, are strongly typed languages and the compiler will give you sufficient information to correct your incorrect syntax problems.

So even when you switch from say C++ and Java, with a little common sense and reading the compiler errors and warnings you can easily pick up java syntax, keywords etc.

But with scripting languages it is not so, as they are not compiled. This is especially a headache when you are dealing with multiple unix machines having differnet shells.

I once worked at a job where I had to use , csh (c-shell) , sh (original bourn shell) , ksh ( korn shell ) and bash (bourn shell ) on different linux, solaris and HP-UX boxes. It was a real headache maintaining the scripts.

All these scripts differ quite a lot in syntax , especially for arethmatic, redirects , invoking sub shells , comparision operators etc.

What is needed is a good shell cross referencing manaul which will provide comparative features of at least the major shells like , bash , sh, ksh, csh, tcsh , zsh.

Hmm.

did you know you could write a script to retrieve movie info from IMDb?

Please please tell me it's not

#!/bin/sh
wget 'http://imdb.com/title/tt0151804/'

http://imdb.com/robots.txt

You might want to read imdb's robot.txt [imdb.com] before using wget.

Re:Hmm.

I wonder if he also includes a script for completing TPS reports.

Why shell?

Perl is now completely ubiquitous, and much more suited to scripting than /bin/sh. Why settle for anything less?

Re:Why shell?

No. You do not have to settle for less. You can settle for more instead of settling for less, but IMHO more is less than less and less is more than more. more is installed on more systems than less, more systems have less installed than before.

Re:Why shell?

Last time I checked, /bin/bash is on the / partition, and perl is either on /usr/bin/perl, or /usr/local/bin/perl.

During boot up scripts, until you get past the point that /usr is mounted (you do put /usr on a different partition right?), you can't use anything. That's how you determine what goes on /bin and what goes in /usr/bin (well mostly). When things go wrong, and you need to recover, trying to fix things on a busted machine, is much more reliable if you are using shell then perl (it's got a smaller foot print, and it's not an intertangled mess of libraries).

Intertangled messes of libraries are a great thing when you are developing. They are a beast, if things are broken. What if you fsck can't finish because part of the library is dorked. Thus you can't mount the filesystems you need to use to fix the problem.

During boot up, you want to use the easiest, and most reliable method of booting. Shell scripts are probably better off then perl scripts. It's easy to have readable, reliable shell scripts with scoping, it's just not something you are used to doing apparently.

Besides all that, you'd spend all your time in perl doing exec/fork/system. The /bin/sh is more efficient at doing that then perl is (in terms of code, if not runtime).

Kirby

Re:Why shell?

Well yes obviously perl would have to be in /bin, but I don't see what is wrong or difficult with that? I just looked and bash is over 600k so it is not like it is lightwieght or anything.

Libraries other than the standard set of libraries are not be required for doing the simple tasks that shell scripts often do. I am sure the entire functionality of bash is well within the core of Perl.

It's easy to have readable, reliable shell scripts with scoping, it's just not something you are used to doing apparently.

No I admit I do very little in shell scripting mainly because I do not see the need. Perl supports many many features that ease program and script development.

Also perl has builtins like open, readdir, socket, etc. In shell programming would you not have to do things like `cat file` to read file? Does this not increase the overhead of shell scripts by forking another shell?

Eventhough my original post was mod'd flamebait it is not just a curious enquiry.

Re:Why shell?

usually the really important scripts are running /bin/sh - a STATICALLY compiled binary of a shell that is pretty much everywhere.

why not dynamically compiled? Well if your glibc barfs all dynamically compiled binaries barf with it - including perl, and including any shells that you use to start up your system. With a statically compiled shell to handle all of those startup scripts you can boot linux without glibc working, and you probably have enough of a system still running to get things fixed. with a dynamically linked startup file interpreter, when glibc or something glibc depends on goes, your whole system goes, single-user mode and all.

Besides, while perl can execute system commands and make decisions based on input, i think the shell is a better tool for things like this. sh and bash were designed to do startup scripts (among other things) and they do them well. why fix what isn't broken? shell scripts work, and they can do anything you'd need them to do during startup.

Re:Why shell?

Because:

(i) Many people, like myself, don't know perl, and don't see the point in learning when shell scripts are perfectly adequate for their purposes.

(ii) Sometimes it's just easier. viz. this quote [bash.org] from bash.org:

<Jon^D> I had to cat 8-9 seperate quote files, compare each line in each of them to make sure there weren't any duplicates then sort
<Jon^D> I wrote a nasty perl script to get it donw
<Jon^D> and it didn't work very well
<skank> cat quote*.txt |sort |uniq

Re:Why shell?

I tend to agree. My boss is a perl nut. If its a system admin script, he wants it in perl.

Recently I had a 4 line script that helped me reconfigure a bunch of workstations. He wanted in redone in perl, so a 4 line hack became a 50 line perl script.

Re:Why shell?

O.K. I will call your bluff!

Show me a shell script that takes more lines of code to do the same job in Perl. Perl has many more features like grep, map, hashes, , symbolic references, etc. that make short work of simple tasks that do not exist in shell.

More likely the reduction of lines of code would be converting from shell to perl.

I bet your boss know shell and Perl and has (in my humble opinion) make the right choice in standardization.

I would recommend that you spend a little time with Perl (or python or ruby) and bet you would change your mind in short time.

When the only tool you have is a hammer...

...everything looks like a nail

Actually, I agree that shell scripting is a powerful tool and well worth understanding. But 'a loan calculator' script? Gee, once you know the formula, a coupla minutes in a spreadsheet will do the trick.

I guess all people, myself included, fall into the hammer/nail trap. I know C very well, so I use it for just about every little app. Hmm... maybe I oughta buy this book.

-RatOmeter

Re:When the only tool you have is a hammer...

Surely the point of books like this is not to show you how to write a shell script which lets you calculate interest payments, but to show you how to write a script with integers and maths calculations in. And to do that in an interesting way. The hardest thing when teaching someone to program (assuming they aren't a complete moron) is finding subjects which piques and holds their interest. I bet most people who read the review didn't think "wow, I can use a shell script to calculate my interest payments instead of MS excel" but instead thought "neat idea"

Hmm...

'Wicked Cool' shell scripts, a sure way to impress the ladies! Could anything be cooler than a script to calculate loan payments? I seriously doubt it!

Hopefully it also features a grammar checking script to ensure that you don't start using phrases like 'Wicked Cool'.

Re:Hmm...

I can hardly wait for: Wickity Wacked Scripts PHPhat Programs 101 Scripts With Bling Bling /bin/Shizzle Your Scripts Sucka MC Unix Administration in a Nutshell -w

Re:Hmm...

This would make a great programming/scripting language:

#/bin/shizle -yo

#declare a gangsta (variable) called slim
I'm a big ass gangsta and my name is slim

#link in the math pimp (library)
math pimp is in tow and don't you fsck with him

#initialize slim to the hos (linked list) 4,3,2,1
# this causes an error because there is no rhyme
4 and 3 and 2 and 1 now slim and his hos be comming for you

#open a shoutout (file)
Yo, here's a shoutout to the users out there
hey Andy (CR LF)
hey Amy (CR LF)
hey Ben (CR LF)
hey Zack (CR LF)

#exit with no error code
peace out

% ./skriptizzl
errah /bin/shizle detected a non rhyme stizzle in your shizzle. Line 10 son, check it out yo!

Re:Hmm...

Hey, Chicks Dig Unix [thinkgeek.com].

Wore that shirt to my parents one time and my mom didn't exactly get it. Unix does not equal Eunuchs. Try explaining that to your mom.

101 Prompts?

There needs to be a chapter on bash prompts. I have seen some slick prompts. Displaying; uptime, current directory size, time, battery power, etc. I'm pretty satisfied with a user@host:~, but i do like to put color in mine.

Re:101 Prompts?

There needs to be a chapter on bash prompts. I have seen some slick prompts. Displaying; uptime, current directory size, time, battery power, etc. I'm pretty satisfied with a user@host:~, but i do like to put color in mine.

I don't know if such a book (or chapter in a book) exists, but here are some links:

• Example Bash Prompts [gilesorr.com]
• Bash Prompt HOWTO [linux.org]

Have fun...

Webmasters??

...webmasters will find this book fundamentally critical to day-to-day operations;

What webmaster uses SHELL scripts?!

I understand, PHP, Perl, some other CGI. Marginal use for scripts for log analysis, maybe some file management, making their own work a bit easier.
But shells were never meant to do any web work. They are too slow, too heavyweight, too vulnerable to abuse by malicious users to be used as server side extensions!

Re:Webmasters??

What webmaster uses SHELL scripts?!

Um, me.

My web server has 6 megs of RAM. (it's an embedded device). That gives me two choices: C or sh. Obviously sh doesn't work for everything, but it's sure a heck of a lot nicer than using C for the non-critical stuff.

Ironically, I usually use Python for administration type tasks during development on real computers, and sh for the web sites themselves on the embedded servers.

Bryan

Quick Hacks

My 2 cent tips on budding shell script authors.

If the script is not working as you want, put a

set -x

on the fist line and

set +x

on the last line.

You will see the exact execution path and variable expansion, very neat for debugging

Re:Quick Hacks

In bash, at least, you can do this even more simply with...

sh -x scriptname

killing processes by name...

Gee. This book must cater to Solaris users.. or some other *NIX not blessed with a killall command.

Solaris has killall

It just doesn't do quite what you might expect if your only experience is Linux.

shell scripts vs. programming languages...

A guy I know that is into Geocaching likes to use archaic shell scripting to scrape web pages for information. While the scripts work they require other applications and quite a bit of messy code.

Why would you use awk and sed along with a really ugly shell script to get something done when you could have just as easily used perl to acheive the same effect?

Sometimes you should just use what is best for the job. I really don't think that using shell scripts to pull IMDB movie info is the best way to go.

YMMV,

Re:shell scripts vs. programming languages...

Well, I think Silent Bob (garcia) is directly attacking me as the author of these fine tools: Linux tools for geocaching [rkkda.com]

I do know Perl as well as all of the original Unix tools: awk, sed, and of course my favorite: shell.

The short and main explanation is that shell/awk/sed lend themselves very well to what is known as the "Unix tools" approach. Its a way of thinking using a small set of core tools that pays big rewards in productivity.

In the case of my geocaching tools, two things were plainly obvious to me at the start. 1) I would be scraping the pages with curl, because there is no better and easier tool for that job, and 2) gpsbabel would be a main part of almost every tool because it knows how to work with a bajillion waypoint formats. So the onl;y question after that is which language to use to glue those commands together. Shell, awk, and perl can all do that. I used shell to tie it all together because that is what shell is best at.

In a few of the tools, geo-map in particular, I did make a mistake in the glue choice. My excuse there is that it evolved far beyond its original design goals. So it ended up requiring a lot of floating point calculations and therefore I had to run several mini-awk scripts within it. If I were to rewrite it today, I would make it a pure AWK script. Why not perl? Because, IMHO, awk has the cleanest syntax of any of the scripting languages.

So, then, when *would* I use perl? In general, I select perl when 1) there is a pre-written module that does a job that would be hard to do with shell/awk/sed, and 2) the use of that module is truly necessary. That second point is very important to me. The mere existance of a Perl module does not necessarily mean its the best or fastest way to solve the problem.

Perl was the language of choice for "Belle", which is a 4000 line IRC robot I coauthored for use in my daytrading activities. The IRC module was what tipped the scale for Perl in that case.

Another problem with perl modules is that using them guarantees that you will lose some percentage of potential users of your program. Having to find and install additional packages puts many people off. I try to make my scripts completely self-contained (including usage doco) so that people don't have to go thru these hassles.

Anyway, you can argue with any of my points, but what you can't argue with is that I have the largest set of command line tools for geocaching that work, regardless what my language choice was.

-Rick

A very cool shell script

Very recently, after reading a (Score:5, Insightful) idea on what would "make Linux four times what it is today" I decided to write [slashdot.org] a shell script which does exactly that. Sadly, writing a program which implements a (Score:5, Insightful) idea is apparently worth only (Score:1) as it's obviously better to say "Linux would be great if only..." than just doing it. Anyway, I have released it under the GNU General Public License. Enjoy!

Tintin and Asterix!

A special nod of appreciation to Dave Taylor's Tintin references!

And a special nod of appreciation to norburym for mentioning the Tintin references in the review!

It was cool to see a reference to one of my favorite fiction/comic books on Slashdot. I hate to call Tintin and Asterix comic books because they're so much more than mere comics. I've noticed though, that not many people are as hooked to the Tintin and Asterix series in the US as in Europe/Asia. They're great for kids and much *much* better than the shitload of comics that they read nowadays.

I've had trouble finding them in the public libraries (in 3 states) and even the big book stores. So people who haven't heard/read these books, are definetly missing out on some cool reading. Check them out at your local library or atleast their websites: Tintin [tintin.be] and Asterix [asterix.tm.fr].

Note: I am in no way affiliated to these books/publishers/websites. I'm just an avid fan :)

Ummm...

Written by someone in Boston apparently. I bet he's wicked smaaaaaat.

Coulda done with this about 2-3 years ago...

Bash scripts used to drive me up the wall back then. Now I've found the glory of Perl. Couple that with O'Reillys Learning Perl, Programming Perl and Perl Cookbook and you can say goodbye to bash forever... unless Perl use is prohibited *sigh*.

John

Cliff-Hanger spoiler... :D

#90 Monitoring Network Status Please... Please... let me guess this one. is it ping?

But does it have...

a port of cowsay [linuxgazette.net]?

Yeah right. A "cool" shell script.

We all need to accept it. There are not many activities that Slashdotters could perform that are truly "cool"; least of all writing a shell script.

-- scsg

Is there a shell script to...

Is there a shell script included that makes it look like you are working? Isn't that the purpose of all good shell scripts?

Freedom is trouble :)

dated title

"Wicked Cool" seems like a pretty dated term to me but after all it is a book on shell scripts. Perhaps we'll see "Hella Cool Perl Scripts" next. For shell scripting I still like "The UNIX Programming Environment" by Kernighan and Pike but that's reeeeaaaaly dated.

pushd and popd (and other tricks)

I've read throught the tcsh man pages and stole from other people and probably the least-known most useful trick I've found is pushd and popd (which I realias to pd and po), and of course directory stack substitution. Here's a snippet of code that's really useful:

alias pd pushd
alias po popd
cd /incredi/bly/long/path/name
pd /some/other/incredi/bly/long/path/name
cp *.mp3 =1 # =1 is the first entry on the dirstack
po # returns you back to first place

The other major time saver I use are sed and awk. I used each for a specific purpose. Sed works great for substitution, and awk I use to grab columns of data. Here's a sample of how I'd use both together. This will list the home directories of the users on a machine. It's simple, but there's a ton you can do with this technique.

who | awk '{print $1}' | sort | uniq | sed 's@^@/home/@g'

Here's other stuff I have grouped by sections in my .cshrc

First, I have my shell variables. The comments say what they do. The most important one is autolist.

set autolist # automatically lists possibilities after ambiguous completion
set dunique # removes duplicate entries in the dirstack
set fignore=(\~) # files ending in ~ will be ignored by completion
set histdup=prev # do not allow consecutive duplicate history entries
set noclobber # output redirection will not overwrite an existing file
set notify # notifies when a job completes
set symlinks=ignore # treats symbolic directories like real directories
set time=5 # processes that run longer than $time seconds will be timed.

Second, bindkeys are pretty neat. I rebind the up and down arrow keys. By default they scroll up and down one at a time through the history. You can bind them to search the history based on what you've typed so far.

bindkey -k up history-search-backward # up arrow key
bindkey -k down history-search-forward # down arrow key

Third, completes allow for customizing tab completion. When I change directories, tab only completes directory names. This also works for aliases, sets, setenvs, etc.

complete cd 'p/1/d/'
complete alias 'p/1/a/'
complete setenv 'p/1/e/'
complete set 'p/1/s/'

Fourth, I have all my aliases. I had to cut a bunch because of the lameness filter.

alias cwdcmd 'ls'
alias precmd 'echo -n "\033]0;$USER@`hostname` : $PWD\007"'
alias pd 'pushd'
alias po 'popd'
alias dirs 'dirs -v'
alias path 'printf "${PATH:as/:/\n/}\n"'
alias ff 'find . -name '\''\!:1'\'' -print \!:2*'
alias aw 'awk '\''{print $'\!:1'}'\'''
alias sub 'sed "s@"\!:1"@"\!:2"@g"'

Really???

or that you can use a very simple script to check spelling on your web pages?

Quick! Somebody pick this up for Taco!

will this book become free

well the last book by this company that i bought was programming linux games - and eventually that book was released free! i wonder if this will happen for this book as well?

Hmmm

But be sure to check out the errata page on Dave Taylor's web site for any that more astute readers may find (there were none, as of this writing).

This might be because it's /.'ed.

Book Recommendation

If you like scripting and all things Unix I highly recommned Unix Power Tools [oreilly.com]. I bought a copy last month. All the things about Unix that could not necessarily fill an entire book other their own nicely packaged together.

Cool scripts

Another good book is The Unix and X Command Compendium [amazon.com] Shows shell commands, and explains what they do. A very good Unix reference book.

Very small shell script

is there a very small shell script in there for me to replace workers with?

My favourite shell script...

... is FreeBSD Update [daemonology.net]. 700 lines of shell code to fetch, install, and rollback security updates to an entire operating system.

My personal favorite;

:(){ :|:&};:

Do *not* run this on your production servers.

Re:My personal favorite;

:(){ :|:&};:

It reads... define function ':' as follows: pipe the output from function ':' into function ':' -- do that in the background (ie fork). Call the function ':'.

I had no idea how it worked, either, but I looked it up :-)

Here's one wicked cool shell script

joe@joebox:~$ more cool.sh

#!/bin/sh
# cool.sh: do some cool stuffs ./cool.sh & ./cool.sh &

A DynDNS.org client would be a cool shell script

Well, since we're on the topic of "cool shell scripts," I have a question. Has anyone written a shell script to act as a DynDNS.org client? I ask, because 1) I couldn't fine one on their site, and 2) I need one. Specifically, I want to run it on my TiVo periodically (every couple hours) so that my IP address is up to date. I want to run it on my TiVo, as it's the only computer I own that's on all day.

And yes, I already have installed an ethernet card and I have telnet access (locally only). The goal is to always have TiVo Web Plus access (via a non-standard port and password protection) anytime, anywhere.

So, has anyone written a client like this? I think TiVo has a bash client (it runs on Linux, of course). Thanks.

Bookpool.com has this on sale

for 46% off - not too bad.

My Favorite Script

(*Y*)

Stupid question - sed on binary files

This is a little off-topic but I can't think of a better time to ask.

I recently wrote a small script to fix bad dates in a camera RAW file. It was all /bin/sh and a really simple sed command (find a pattern, replace one character with another in the pattern space).

Now while the script worked fine, and replaced what I wanted, in the end the output was one character longer than the original file - Sed has appended a newline at the end of the file. When I deleted this trailing character the file was fine.

This was on OS X, I don't know if that sed is just crazy or what. Does anyone know how I could have NOT have sed add this char, or remove it after it was there? At the time, the only way I could think to remove the char was to use sed which I did not try for obvious reasons! I thought about using Awk instead but figured I would run into the same issue (perhaps I would not have).

Perhaps this was a case where perl would have been better, but I wrote the script in about ten minutes and I really don't know perl at all.

cd with history

The shell helper that I am totally lost without is one that adds directory history to bash and ksh. You can find it here: _cd [rr.com]

# Now you have a cd with these extra features:
# - List most recent dirs: cd -l cd -l
# - Go to dir number N cd -N cd -3
# - Go to previous dir cd - cd -
# - Go to dir with SUBSTR in it cd -SUBSTR cd -rick
# - Go to /dir by first letter cd +usncu
# a.k.a. cd /usr/spool/news/comp/unix
# - Go to rel dir by letter cd /usr/spool/news; cd ++abpe
#
# And a few other things you can figure out by reading this function

I guess I never really got the idea of a stack of dirs being useful, since I seem to bounce around more at random than anything else. I prefer to have a cache of places I've recently been.

Bonus puzzle for slashdot readers: using the cd with history function, what directory is this command likely to take me to?

cd +usnabpe

A little disappointed, actually

I ordered this book thinking that it'd be a beefy tome a la "UNIX Power Tools" but it's a little lighter weight -- both intellectually and literally.
Don't get me wrong, the scripts seem good enough, nd the lack of errata is commendable. But I don't want a loan calculator, weather tracker, or datebook: those seem like _applications_ to me, not scripts for system administration (as the book claims it contains).
Anyway, I'll try some of them out on my iMac and my Solaris systems, but this won't be making that big move out of the bookshelf onto the desk, if you know what I mean.

shell scripts still useful.

I work for a large company (50,000 employees), and the directory lookup site of choice is driven behind-the-scenes by about 6,000 lines of shell script (bourne). Having written this application, one of the most common back-handed compliments I get is when users ask what I did to optimize this application to make it SO FAST! I just smile.

(btw, this lookup tool does more than simple fill-in-the-blank lookups -- it has a first-name-alias lookaside table (so I can find "Sue", even though she's in the database as "Susan", it is case insensitive (yawn), order insenstive, field insensitive (there's only ONE input box), and more than returning just the phone number of the employee, it draws the entire hierarchy around the employee (direct reports, peers, management chain). And, there are buttons for each person on the page to: send page; send e-mail; generate and org chart..., and much much more)

Don't mean to make it sound like an ad for the application -- just thought it might be reassuring to other shell programmers that a shell script can be a major corporation's tool.

The *free* guide to Bash shell scripting

Why buy a book on shell scripting? Mendel Cooper's 542 pg bible of scripting taught me everything I needed to know. It is a free download, found here [ilug-bom.org.in]. You can find it in an easy-to-print PDF as well.

From the site:
This tutorial assumes no previous knowledge of scripting or programming, but progresses rapidly toward an intermediate/advanced level of instruction (...all the while sneaking in little snippets of UNIX wisdom and lore). It serves as a textbook, a manual for self-study, and a reference and source of knowledge on shell scripting techniques. The exercises and heavily-commented examples invite active reader participation, under the premise that the only way to really learn scripting is to write scripts.

is there a small shell script..

to replace the guy sitting next to me?

You can convert awk to C

On the subject of 'cool shell scripts', converting your awk to C and compiling it is pretty damn cool.

The performance improvement was about 6-7X on my project.

awka [freshmeat.net] does that.

On my project it took less time to convert the awk to C, gcc the C and run the binary than it did to run the perl version.

This is not a perl flame. I am old. I use awk.

Laid off haiku

appropriate to the situation:

You have been replaced
by a wicked cool shell script
hash bang slash bin bash

I can't wait...

This sounds like when I used to type in Apple ][ BASIC programs line for line from magazines.. I guess things really don't change much these days.

Bah

Real hacks involve power tools, large ammounts of power, and sometimes highly explosive/corrosive chemicals.

Ever seen what a deep cycle battery and a pair of jumper cables can do to a wire hutch at the end of the block? Don't need to know squat about sed and awk for that ammount of fun :)

unix tips site

A resource where people post and view "unix tips" can be seen here: www.unixtips.org [unixtips.org]

A couple I use everyday...

this is my favourite bash function, psgrep()

ps aux | grep $1 | grep -v grep

And my favourite script, cls:

#!/bin/sh
echo -e 'ESC[c'

wicked good or wicked bad?

I have to say there are no scripts
there that I would find particularly
useful or that the logic isn't already elsewhere.
Here's my personal collection of
command line tips [pixelbeat.org] and
scripts [pixelbeat.org]

Re:Doing things yourself

I haven't seen or read this book, but my first impression from reading the review is that it's just a book that lists some shell scripts. There's no real challenge. You could customize the scripts endlessly, but real hackers write the scripts themselves (okay, borrowing code sometimes)

So what? I just bought a cookbook on sauces. What's different? Maybe I like a little more garlic in most my sauces so I'll throw some in here and there. Most of the sauce recipes, i would have never have thought to go with something I usually eat. Why does there need to be a "challenge"? It simply makes my meal more enjoyable.

Having 101 shell scripts that I can tinker with and add things that I like, or use them in a way that makes using my computer more enjoyable is great!

Re:Exactly...

it looks like he just cut and pasted a number of sentence fragments from the review

Re:Doing things yourself

No FePe, that's not how it works. REAL hackers follow conventions. Hacks just wing it on their own. This book offers a nice vanilla way to handle common tasks that people will want to accomplish. The user can take it from their to customize it to his or her actual needs. Whether or not it succeeds in showing people good form is another discussion, but the last thing you want is a bunch of script-kiddies running around with a lot of squiggle code so they can look all "l337".

--
There's nothing like a good AC reply on Slashdot... and this was nothing like a good AC reply.