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Windows PowerShell in Action
jlcopeland writes "For two decades I've hated the command prompt in DOS and Windows.
Inconsistencies abound and everything is a special case. The
fallback on a Microsoft box has been running a Unix shell under Cygwin or
installing Microsoft's
own Services for Unix (or its predecessor, Softway's Interix),
or by scripting in Perl, but those only get
you so far. Having co-written nine years worth of trade rag columns
using mostly Perl as the implementation language for the samples,
and thinking of every problem that comes across
my desk as an excuse to write a little bit of scripting code,
I've got some well-formed views about scripting languages
and what works and what doesn't. That means
I've been eagerly watching the development of PowerShell since it
was called Monad. It's got the advantage of being a unified command-line
interface and scripting language for Windows, even if it does have
a dorky name." Read the rest of Jeffrey's review.
Windows PowerShell in Action
author
Bruce Payette
pages
576
publisher
Manning
rating
9
reviewer
Jeffrey Copeland
ISBN
1932394907
summary
Guide to PowerShell, the new Windows scripting language
Bruce Payette's Windows PowerShell in Action is a great overview of PowerShell, aimed at an audience that's got some experience with other scripting languages. Bruce's book is a big improvement over Andy Oakley's earlier book, Monad, which I had been using: it's more complete and it's up-to-date for the first release of PowerShell. It's got great (and sometimes amusing) examples, and feels like the Perl Camel book in flow. When I was reading it in the gym or someplace else away from the keyboard, I kept wanting to run back to the office to try something out. There are also useful "why it works this way" digressions, which provide a lot of context. Since Bruce was on the original development team, wrote most of the commandlets, and was responsible for much of the language design, those digressions are more authoratitive than the directors' commentary tracks on most DVDs.
In outline, the nine chapters in the first part of the book build up as you'd expect: overview and concepts, to data types, to operators, to regular expressions, to syntax, to functions, to interpreting errors. It covers that ground better than many language books that now litter my shelves. The explanations are clear, and the examples are almost all exactly on point. It took me a second reading to realize that my complaints about the regular expression sub-chapter wasn't about the chapter itself, but about some of the implementation decisions; that's an argument about style more than substance, and an observation about me, not about Bruce's writing or PowerShell. The first part of the book is the "mandatory reading," if you will, to get the language down and begin exploring on your own.
The second part is where the real applications are covered. That's the part that you especially want to read sitting next to the keyboard. As you'd expect, the example code is available from the publisher's web site to start you off — look for "Example Code" under "Resources." There's a very good discussion of text processing and how-to-handle XML, complete with some not-obvious warnings about traps to avoid. I've been working very carefully through the really good chapter on using GUIs with PowerShell, "Getting Fancy — .NET and WinForms," and my own proof of concept for that has been rebuilding an old C++ data entry application into a much simpler PowerShell script. As a nice side effect, Bruce's book (and the WinForms chapter in particular) provide a gentle overview to some concepts in the .NET framework, which I hadn't had an opportunity to delve into. The appendix on using PowerShell as a management application will be especially useful to system managers; that was one of the original PoweShell target audiences, and the language achieved that goal very well. The appendix on the language's grammar is really useful, and I keep flipping back to it to check on things.
After Oakley's Monad appeared, there was a long gap before the next PowerShell book appeared. Bruce's book looks to be the first of the post-release wave. If all it had going for it was the authoratative pedigree of the writer, it might be worth it, but it's also well-written, well-organized, and thorough, which I think makes it invaluable as both a learning tool and a reference.
You can purchase Windows PowerShell in Action from amazon.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Bruce Payette's Windows PowerShell in Action is a great overview of PowerShell, aimed at an audience that's got some experience with other scripting languages. Bruce's book is a big improvement over Andy Oakley's earlier book, Monad, which I had been using: it's more complete and it's up-to-date for the first release of PowerShell. It's got great (and sometimes amusing) examples, and feels like the Perl Camel book in flow. When I was reading it in the gym or someplace else away from the keyboard, I kept wanting to run back to the office to try something out. There are also useful "why it works this way" digressions, which provide a lot of context. Since Bruce was on the original development team, wrote most of the commandlets, and was responsible for much of the language design, those digressions are more authoratitive than the directors' commentary tracks on most DVDs.
In outline, the nine chapters in the first part of the book build up as you'd expect: overview and concepts, to data types, to operators, to regular expressions, to syntax, to functions, to interpreting errors. It covers that ground better than many language books that now litter my shelves. The explanations are clear, and the examples are almost all exactly on point. It took me a second reading to realize that my complaints about the regular expression sub-chapter wasn't about the chapter itself, but about some of the implementation decisions; that's an argument about style more than substance, and an observation about me, not about Bruce's writing or PowerShell. The first part of the book is the "mandatory reading," if you will, to get the language down and begin exploring on your own.
The second part is where the real applications are covered. That's the part that you especially want to read sitting next to the keyboard. As you'd expect, the example code is available from the publisher's web site to start you off — look for "Example Code" under "Resources." There's a very good discussion of text processing and how-to-handle XML, complete with some not-obvious warnings about traps to avoid. I've been working very carefully through the really good chapter on using GUIs with PowerShell, "Getting Fancy — .NET and WinForms," and my own proof of concept for that has been rebuilding an old C++ data entry application into a much simpler PowerShell script. As a nice side effect, Bruce's book (and the WinForms chapter in particular) provide a gentle overview to some concepts in the .NET framework, which I hadn't had an opportunity to delve into. The appendix on using PowerShell as a management application will be especially useful to system managers; that was one of the original PoweShell target audiences, and the language achieved that goal very well. The appendix on the language's grammar is really useful, and I keep flipping back to it to check on things.
After Oakley's Monad appeared, there was a long gap before the next PowerShell book appeared. Bruce's book looks to be the first of the post-release wave. If all it had going for it was the authoratative pedigree of the writer, it might be worth it, but it's also well-written, well-organized, and thorough, which I think makes it invaluable as both a learning tool and a reference.
You can purchase Windows PowerShell in Action from amazon.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Named after the designer lost a testicle in a tragic chair throwing accident.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
...in 20 years MS will invent UNIX.
Powershell is very powerful. Much more so than cmd.exe. I don't have significant enough experience with bash to compare the two but I would not be surprised to learn Powershell equals if not beats bash at the shell game. I wouldn't say it is ready to replace any of the scripting languages just yet.
I have been using it for a while now and the single (semi-major) problem I can find is memory usage. It is a hog at best, and at worst when you are using it semi-heavily it can easily chew up 1GB of memory. That's even with giving the GC something to work with, ie unsetting $vars when you are done with their data.
I wish they'd kept "monad" as the name. It was a deft tip of the hat to Leibniz's Monadologie, which held that monads were the windowless metaphysical atoms of perception itself.
Inconsistencies abound and everything is a special case.
You should switch to bash and the GNU tools.
Oh, wait.
Proud member of the Weirdo-American community.
Now all we need is for Sun to develop a Solaris-only shell, Apple to develop a Mac-only shell, and RedHat to develop a Linux-only shell. I hate re-using code because it forces me to solve new problems every day. I'd rather create new value on Mondays only, and then spend the rest of the week re-doing the same work on my other platforms. It gives my mind a chance to rest, and I can drink heavily mid-week and still be able to do my job.
I sure hope they charge extra for it, make it a resource hog, lock out third-pary extensions, and then discontinue it as soon as I'm dependant on it. I really liked the 1980s and look forward to reliving them.
I don't use Monad (:s/M/G/g) or intend to, so I don't care much about the book. But what a great review. We get a lot of amateur reviews around here, but this one was particularly well written, clear, and informative. Nice job, homie.
If this were Usenet, I'd killfile the lot of you.
Windows Powers Hell ?
I guess I always suspected it was true, but the beastie mascot of BSD made me wonder if there wasn't room for a little UNIX in Hades too.
Use the Firehose to mod down Second Life stories!
It's slower than cold molasses up a hill.
It takes a few seconds for the prompt to appear, and if I run a "dir" operation with both cmd.exe and PS in a directory with hundreds of files, cmd.exe will beat it in seconds.
I'm not running a slow machine(core duo 2, 1GB of RAM). Is there something that needs to be configured to make it suck less?
I would argue most power users don't need a shell.
.NET String object has an API that's a lot easier than sed and awk.
:-)
I'd say that power users who think they don't need a shell don't know what they're missing ; they could have a lot more power.
The gentleman sitting next to me has recently discovered and raves about WinGrep, a GUI file search/replace utility with RegExp support. It's not bad, but it can't compare with a shell - you can't, for instance, search for a bunch of files containing your desired pattern match and invoke an external utility to process each one. And anything that the original application designer didn't visualise as a feature is excluded. He's easily capable of comprehending grep and sed, which would do the same job for free, but he's more comfortable with the GUI.
In a *nix style shell, the ability to pipeline STDOUT through a whole bunch of little utils is the tool of a real power user - and it has a nice easy learning curve, you can pick up new commands as and when you like, and combine them with old favourites. The downside to the *nix shell is that very often you have to perform some esoteric text processing to get what you want, which means learning tools like awk and sed. Powershell works by passing objects through the pipeline - objects that have useful properties. It's even an improvement with old-style executables that emit pure text - the
The GUI equivalent of a shell for a power user would be a pipeline composer where you can take various widgets representing actions and plug them together. Perhaps something like the DTS transform designer in SQL Enterprise Manager. Or maybe not
I really, really want the Linux CLI to be modernized. (Lots of time is spent working on the Linux GUI, but it seems like when it comes to the CLI people are content to let it rot.) I've spent a lot of time trying to figure out how I would go about doing that. I've read a bit about PowerShell - it seems interesting, at least, and promising. For instance:
- It can wrangle live
- It encourages a unified interface (conventions for command options, etc.) for CLI programs and utilities
- It applies these new techniques in conjunction with existing, traditional shell mechanisms, like pipes.
- It endeavors to make documentation and general information about commands easier to access
Now, there's also things I don't like so much - for instance, the distinction between "commandlets" and normal commands. (To be fair, this is largely due to the fact that most existing code in the world is written either for a traditional CLI or a GUI - so most code isn't going to know how to deal with a smart CLI anyway. But I think there are better solutions.)
I think it's kind of a drag that Microsoft may now have a better CLI than Linux - but I think that's a situation that can be changed.
---GEC
I'm but the humble pupil, seeking to snatch the scratchbuilt pebble from the master's fully articulated hand
Any sufficiently recent Microsoft OS contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Unix.
"Not an actor, but he plays one on TV."
it treats piped arguments as objects instead of strings, Psh lets programs access the data directly, instead of having to manipulate large amounts of textual data with tools such as grep or PERL.
Then they have absolutely no idea about what they are doing. The one big advantage in using pipes is that any application can handle text data.
Let me give one example: I use the sort command all the time, it sorts data by lines of text, lines are compared according to criteria passed in command options.
Now, imagine if it depended on binary objects. For every sort operation one would have to write a comparison function to decide which object should come before the other. Writing a special function would mean declaring some form of callback, or maybe some people would call it a closure, whatever. And so on.
Here's one simple command I use when a disk starts getting full to see which directory is the data hog:
du -x / | sort -nr > mem.txt &
What this command does is check the disk usage (du command) in the root directory (/) without looking at symbolic links to other disks (-x option). The result is piped to the sort function, where it's sorted by the numeric value of the first column in reverse order (-nr option). The sorted result is sent to a file named mem.txt. Since checking the whole disk may take some time, it's done in the background (& command). After it finishes, I have a file with the size of each directory in the disk, one line per directory, ordered by size, larger directories first.
See how powerful it is, having data represented as text? Try writing this line as a Powershell script.
Another advantage of having data in text format is that you can test it using the keyboard and screen very easily, no need to run a special debugger.
Instead of trying to reinvent Unix poorly, Microsoft would do a favor to its customers if they accepted Unix is a mighty fine OS and adopted without shame its best features.
I strongly disagree with most of what you've said. Here's why.
.NET provides this, of course. Similar technologies could provide the same thing on Linux. It's a tall order, mainly because of all the programs in the world that are written for naive assumptions about the shell environment...)
The supposed "ease" of dealing with text is an illusion - it's a fallacy that's built out of
1: the fact that textual formats are usually organized such that we humans can read them if we send the data out to a console
2: the fact that Unix types have built up a formidable array of text-wrangling utilities to deal with these problems
3: a general assumption that the reading and writing of formats passed between processes won't pose any real challenge to process.
The relative "ease" of text is negated if three corresponding conditions are met in a shell dealing in structured data:
1: Data is structured (or information about the structure of the data is communicated) using mechanisms that are respected by all tools involved. (In other words, there's some kind of Lengua Franca for the structured data -
2: The structured data that is used in inter-process pipelines is given suitable (preferably interactive) display methods
3: An appropriate set of data handling tools are introduced, generic enough to work for most problems and powerful enough to be effective.
The problem with textual formats for structured data is that there will always appear ways that you can do it wrong. For instance, what if a field contains the character (or set of characters) you're expecting to use to delimit the fields? Well, that's why find has a -print0 option, isn't it? Now, what if the field could contain null bytes, too? Then maybe you use escape characters - and the process of reading in the output from the previous command starts to become a more complicated parsing problem.
You cite how easy it is to sort based on a field (and, to extend the exam
---GEC
I'm but the humble pupil, seeking to snatch the scratchbuilt pebble from the master's fully articulated hand
If you look at Powershell, they've got the "read immediately" process down - commands like "Format-Table" come to mind. Yeah, big deal, right? It's what PERL was born to do. But nevertheless - if you run a command and it generates an object, a meaningful printed representation of that data appears on the console. If you want it to look nicer, there are commands to format the output. I think the shell would be better if the user didn't need to handle that step explicitly - I have some ideas for how that could be done. (I am very interested in writing a Linux shell with these kinds of capabilities.) This makes it trivially easy for programmers to modify the output, or for the users to use it in unexpected ways. It means we don't need a separate program to convert binary data to a human-readable form first. From my perspective you've got it backwards. Every single program in a pipeline chain is burdened with the job of converting "human-readable" data to a useful, processable form - and then back to text again for the next chump in the line. So maybe you save one step, because you don't need to reformat the output of your last command - but you've added on two steps for every command in the chain (minus one, for the first) - and when programs start to get even moderately outside the realm of the common, everyday stuff, the user starts having to deal with those processes themselves. Complex datatypes in a shell are only good if you're using a set of languages that can deal with the same objects. With Unix, not all your languages have a concept such as an object -- not even a struct. Even then, you need a human-readable form for them, even if they're converted at the user's request.
As long as Monad has that, it's probably decent. But that's going to be application-specific. True, that is a problem. Not so much the languages' limitations in handling objects - that's just syntax. You can write object-oriented code in C if you feel like it, and certainly C can interface with object managers like CORBA - it just wouldn't be especially fun. It's more the problem of having a common communication format - that's a hard sell because people don't think they need it, and it's a bit of a tall order to mandate something like that.
In what sense is Monad's pipeline communication format "application-specific"? It can deal with any
---GEC
I'm but the humble pupil, seeking to snatch the scratchbuilt pebble from the master's fully articulated hand
Imagine someone gave you some library code, but to use the code you couldn't pass in variables, objects, or whatever. Each function in the library takes one input -- a string. The return from the functions are also one output -- a string. You need to convert this to/from any meaningful format in order for you to use it. That is bash.
Now imagine the same thing, but instead of passing in strings you could pass in/out native data types, full objects, other methods, etc. That's PowerShell.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
Actually, that is PowerShells biggest weakness as a integration shell.
The idea benind the Unix toolset and shell is that everything is reduced to a common lingo -- a character stream. Each tool can then be "used as designed", or "misused". The classic example is the original Unix spell implementation. The tool designer promises to accept as wide an input range as possible, to output consistent streams, and not be verbose.
The actual use (misuse) to the tool is left to the shell and user.
The Object philosophy means that input to a tool MUST have certain methods available. If the correct methods are not implemented over the object, an adaptor tool must be used. Microsoft ensures that all PowerShell tools work together IN NORMAL USE. Obvious "misuse" is not (necessarily) supported.
This makes common usage cases easy, but makes "outrageous" cases almost impossible (unless you reach for VC++ and write your own adaptors).
As an example -- I do a lot of "performance analysis", which entails examination of log files, conversion to normalized scales, and running the results through GNU Plot to get images to paste into reports. There is almost always a need for custom shell scripting to do the log examination and reduction.
Now, this IS possible in PowerShell, but only by treating it as a "Unix (gasp, how horrible!)" type shell.
Since the exploration phase (and creative "misuse") is my primary area, PowerShell doesn't have much to offer me. But, for a developer living in the straight and narrow land of "how it should work", it is probably the next best thing to sliced bread.
As to the "PowerShell" equivalent of the non-Microsoft world: I find that I still (occasionally) cook up SNOBOL scripts. When writing compilers for an old course, it was the ONLY programming language specifically not allowed for assignments (it made lexing, parsing and generation much too simple).
Just another "Cubible(sic) Joe" 2 17 3061
There is, however, no universally agreed syntax for "objects". Sure, there have been attempts, but I doubt any of them will succeed, maybe ever. Different systems have so vastly different opinions of what an object is, and I believe that is how it should be, because if all systems would have to have the same idea of an object, you would be locking them into a predefined design pattern, and innovation might decrease. I don't know if maybe people said the same thing about bytes in the 50s and 60s, so I wouldn't bet my prediction will turn out to be correct, though.
Of course, this is perfect for Microsoft. They don't want other systems, anyway. As long as anyone can agree on the .NET definition of an "object", Microsoft will be happy. However, even then, the fact remains that not every .NET object is serializable -- you can't just take an arbitrary object and squirt (pun intended) it over the network or store it on disk. As long as you wish to communicate with anything outside your own VM, text (or at least a byte stream) is necessary.
Heh, that's one of the weirder statements I've seen as of late. Kind of like saying that you can't "speak" in a telephone, it's just a PCM stream anyway. Call me weird, but I'd argue that text is human readable by definition. I do (kind of) see your point, though, but I don't agree. Text is always human readable, because it has such an internal structure that makes it human readable with an extremely simple and universally standardized (except for charset) algorithm. If you just have an "object", though, there's no universal algorithm for turning it into a visual structure. Usually, each object class even has its own such algorithm, which isn't usually reversible (unlike text), and not every class even does. To begin with, there is, as I wrote above, no guarantee of any sort that an object is even slightly serializable.Not that I think that you're wrong in every possible way. I definitely think that an object-oriented shell may have its virtues, but it's never going to work outside its own VM. Text is universal, since you can send it anywhere and receive it from anywhere. That "anywhere" includes a human, too.