TweetFollow Us on Twitter

September 96 - MPW TIPS AND TRICKS: Automated Editing With StreamEdit

MPW Tips and Tricks: Automated Editing With StreamEdit

Tim Maroney

In this column in Issue 26 of develop, I showed you a wide range of scriptable editing commands available from the MPW Shell. This time I'll discuss a single tool that provides a powerful self-contained text-editing scripting language, StreamEdit.

Why would you want to use StreamEdit instead of the other text-editing features of the MPW Shell?

  • Performance -- A StreamEdit script is faster than an MPW script containing various Replace and Find commands.

  • Self-containment -- Because StreamEdit is a self-contained tool, you can run it from within ToolServer, unlike the scriptable editing commands discussed in Issue 26, which are available only in the MPW Shell itself. This means you can use StreamEdit to create lightweight drag-and-drop grinder AppleScript scripts that send StreamEdit commands to ToolServer.

  • Consistency -- Keeping all your editing in a single scripting language confers the elusive mystical boon of code consistency, making your system easier to maintain and modify in the future.


GETTING TO KNOW YOU

StreamEdit is based very closely on the hoary UNIX tool named sed. If you already know sed, much of this will be familiar, but StreamEdit isn't directly compatible with sed scripts. StreamEdit implements a pattern-matching language. Every time a particular pattern is matched, a sequence of commands will be executed. As in most pattern-matching languages, StreamEdit's scripts are lists of pattern/command pairs, with the pattern coming before the command. The input file or files are read through the script interpreter, which searches for instances of the patterns and executes the corresponding commands. Anything that doesn't match a pattern is passed through unchanged.

StreamEdit scans one line at a time through the input, matching its current line to every pattern in its script. After processing each line, it writes out the modified line. The result is a concatenation of three internal buffers: the insert buffer, then the edit buffer, and finally the append buffer. The edit buffer gets filled with the current line, while the other buffers are empty at the start. The Insert and Append commands place text in the insert and append buffers, allowing you to add text to the beginning and end of the output line. The Change, Delete, and Replace commands modify the contents of the edit buffer.


SHARING ADDRESSES

As usual, MPW uses words in ways previously unknown in human speech. In StreamEdit, patterns are referred to as "addresses." There are two kinds of addresses: line numbers and regular expressions. Line numbers ought to be self-explanatory, but it may help to note that the numbers must be Arabic numerals rather than Roman, and must be in base 10 rather than the hexadecimal or sexagesimal number systems. There are three special line numbers:
  • the bullet symbol (Option-8), meaning the point before the first line (enabling you to add a line before the first line, for example)

  • the infinity symbol ([[infinity]], Option-5), meaning the point after the last line

  • dollar sign ($), meaning the last line
    The keyboard shortcuts, as always in this column, are for American QWERTY keyboards; if you've got some other type of keyboard, you're on your own.
Regular expressions are expressions that manage their diets sensibly. They can be used for searching, and were explained in detail in Issue 26. In StreamEdit addresses, though, regular expressions find the entire line containing the pattern, rather than just the pattern. Regular expressions are denoted by slashes. Only forward slashes are used (StreamEdit doesn't have a backward search mode, having been frightened at an early age by the legends of Eurydice and Lot's wife). Three new constructs have been added to regular expressions in StreamEdit:
  • ç (Option-C), which indicates a case-sensitive search

  • // (two slashes), which means the last regular expression that was matched

  • <=variable>= (a variable name embedded in inequality operators, here overloaded as a special kind of angle brackets, and typed as Option-comma and Option-period), which means the text of an expanded StreamEdit variable, treated as literal text to be matched rather than as a regular expression
StreamEdit has variables that can be set with the Set command (more on this later) or from the command line using the -set variable [=value] option.

You can form more complex addresses using a few operators. The Boolean and, or, and not operators are the same as in C (&&, ||, and !, respectively). Parentheses can be used for grouping within addresses. The comma operator matches the range of lines specified; for example, 3,5 matches lines 3 through 5. A range address matches each of the lines in the range, if any. It can be thought of as matching more than once: it fires off the accompanying command on the first line matched, the last one matched, and all lines in between. If the termination condition is never met, the address continues to match until the end of input. This could happen if you specify a range of lines ending at line 15, for instance, and there are only ten lines in the file, or if your range termination condition is a regular expression that doesn't appear anywhere in the input.


TAKING ACTION

Matching patterns is very nice, but what do you do once you match them? Statements in StreamEdit attach actions to patterns. An action consists of one or more commands, separated by semicolons or by the end of a line. There's no begin or end bracketing as in Pascal or C. Addresses and commands are syntactically distinct, so the script interpreter can figure out where the list of commands for a pattern ends and the next pattern begins.

Editing commands

  • Insert text [-n] -- Adds the specified text to the start of the line by putting it in the insert buffer. The -n option (in this command and in Append and Change) prevents adding a newline when the line is written out.

  • Append text [-n] -- Adds the specified text to the end of the line by putting it in the append buffer.

  • Change text [-n] -- Changes the line to the specified text by replacing the contents of the edit buffer.

  • Delete -- Clears the edit buffer.

  • Replace [-c count] /pattern/ text -- Replaces the pattern with the specified text. This is the second part of a two-step matching process: first the address matches a line, then Replace searches in the edit buffer and replaces the pattern. The count argument indicates the maximum number of times to perform the replacement in the line. It can be a positive integer or infinity ([[infinity]]). The default count is 1.

Control commands

  • Exit [status] -- Stops StreamEdit with the given error status. The default is 0, which means execution completed with no errors. Any nonzero error status indicates a problem, and unless the built-in MPW variable Exit is set to something other than 0, this will stop execution of the script (if any) from which the StreamEdit command was executed.

  • Next -- Somewhat like the C keyword continue. When a Next command is executed, all pending changes are written out and no more addresses are matched against the current line; that is, StreamEdit immediately goes on to the next line without matching the rest of the rules against the current edit buffer.

  • Set variable text [-i | -a] -- Much like the MPW Shell Set command. The variable is set to the specified text. The -i and -a options allow text to be added to any existing setting of the variable at the start or the end, respectively.

Output commands

  • Print [text] [-appendto | -to file] -- Writes output to a specified file. If text is empty, the current line is printed without modification. The -appendto and -to options write at the end of the file or overwrite the file, respectively. If no file is specified, standard output is used. If the file name is empty, nothing gets printed.

  • Option AutoDelete -- Deletes all input lines, leaving only output from Next and Print commands. You can get the same effect by specifying the -d option on the StreamEdit command line or by including this in the script:
/~/   Delete
The text arguments to these commands are usually literal text, denoted by single or double quotes. There are a few other forms as well:
  • An unquoted variable name can be used, in which case the variable is expanded; no brackets need be (or even may be) supplied.

  • A period means the current input line up to but not including the newline at the end.

  • As discussed in Issue 26, you can use reg. (Option-R) followed by a digit to mean the expression with that number matched in the pattern.

  • You can read text from a file with -from filename, which reads the next line of text from the specified file. The filename is usually literal text, but it could also be a variable, the current input line (denoted by a period), or a reg. expression.

A HYPOTHETICAL EXAMPLE

Let's say you're the director of corporate communications at a major computer maker and, without any warning except for inventory backlogs larger than the gross national products of many developing countries, you experience a sudden transition in chief executive officers, corporate policy, and product line. Your quarterly report (10-Q) is due in the SEC's EDGAR database tomorrow. Fortunately the SEC requires the cutting-edge ASCII format for its filings, and you realize that you can automate 90% of the tedious changes with a single StreamEdit script.
# Change nickname of CEO
/Diesel/
Replace // 'Flyboy'
# Change corporate policy
/1,$/
Replace /capture market share/ 'survive'

# Remove lines referring to obsolete products
/PowerTalk/ || /eWorld/
Delete

# Change developer relations strategy
/third-party developers/
Replace /evangelize/ 'listen to'

# Mark lines referring to old schedules
# with a distinctive string at the start
# of the line for manual editing later
/1996/
Insert 'WHOOPS: '

# Add new final line of report
[[infinity]]
Append 'May God have mercy on our souls.'

CONTROL YOURSELF

StreamEdit is almost too powerful. People have used it for everything, including pretty-printing source code, converting files to HTML, and postprocessing object files for dynamic linking tools. If you use it for finding incriminating passages in coworkers' e-mail, karma may get you, but the limitations of the tool won't. Use your powers for good rather than evil, and a grateful world will thank you.

TIM MARONEY has appeared professionally in newspapers, magazines, compact discs, videotape, and of course, computer software. Tim is a technical lead in human interface software at Apple and is editing a series of books for a horror publisher. His skin burns easily in the sun and tans in the moon. He uses white T-shirts only for house painting and car repair.

Thanks to Arno Gourdol, Alex McKale, and Robert Ulrich for reviewing this column.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

WhiteCap 6.7.1 - Visual plug-in for iTun...
WhiteCap is a sleek and sophisticated music visualizer and screensaver that features futuristic, wireframe mesh visuals with dynamic backgrounds and colors. WhiteCap contains thousands of visual... Read more
DiskMaker X 6.0 rc5 - Make a bootable OS...
DiskMaker X (was Lion DiskMaker) helps you to build a bootable drive from the official OS X installer app (the one you download from the Mac App Store). It detects the OS X Install program with... Read more
Lyn 1.9 - Lightweight image browser and...
Lyn is a fast, lightweight image browser and viewer designed for photographers, graphic artists, and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it delivers... Read more
MacFamilyTree 8.2.1 - Create and explore...
MacFamilyTree gives genealogy a facelift: modern, interactive, convenient and fast. Explore your family tree and your family history in a way generations of chroniclers before you would have loved.... Read more
LaunchBar 6.9 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
LaunchBar 6.9 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
MacFamilyTree 8.2.1 - Create and explore...
MacFamilyTree gives genealogy a facelift: modern, interactive, convenient and fast. Explore your family tree and your family history in a way generations of chroniclers before you would have loved.... Read more
Spotify 1.0.57.474. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
VOX 2.8.26 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
beaTunes 5.0.1 - Organize your music col...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more

Latest Forum Discussions

See All

This War of Mine gets a new ending and m...
This War of Mine just got a big new update, featuring free DLC that adds a new ending to the game, among other exciting changes. The update is celebrating the game's two-year release anniversary. Apart from the new ending, which will be quite... | Read more »
Summon eight new heroes in Fire Emblem H...
Nintendo keeps coming at us with Fire Emblem Heroes updates, and it doesn't look like that trend is stopping anytime soon. The folks behind the game have just announced the new War of the Clerics Voting Gauntlet, expected to start next Tuesday. [... | Read more »
The best deals on the App Store this wee...
iOS publishers are pulling out all the stops this week -- there's a huge number of seriously great games at discounted prices this week. Let's not waste any time and get right down to business. [Read more] | Read more »
The House of da Vinci (Games)
The House of da Vinci 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enter The House of Da Vinci, a new must-try 3D puzzle adventure game. Solve mechanical puzzles, discover hidden... | Read more »
Solve the disappearance of history’s gre...
Blue Brain Games invites you to indulge in an immersive hands-on 3D puzzle adventure in similar vein to The Room series, with its debut release The House of Da Vinci. Set during the historic period of the Italian Renaissance (when Leonardo himself... | Read more »
Age of Rivals (Games)
Age of Rivals 3.3 Device: iOS Universal Category: Games Price: $.99, Version: 3.3 (iTunes) Description: Deep civilization-building strategy in a fast-paced card game! | Read more »
Panthera Frontier (Games)
Panthera Frontier 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Angry Birds Evolution beginner's gu...
Angry Birds changes things up a fair bit in its latest iteration, Angry Birds Evolution. The familiar sling-shot physics mechanics are still there, but the game now features team-based gameplay, RPG elements, and a new top-down view. With all of... | Read more »
Sega Forever is for the retro game fans
Sega is launching a new retro games service titled Sega Forever, in a move that's sure to delight games enthusiasts with a bit of nostalgia. Sega's releasing five classic games for free. The titles include Sonic the Hedgehog, Phantasy Star II,... | Read more »
The Little Acre (Games)
The Little Acre 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

ABBYY TextGrabber 6 for iOS Implements Instan...
ABBYY has announced the release of TextGrabber 6.0.0, an important feature update to the company’s productivity app developed for iOS and Android devices. TextGrabber 6.0 now offers Real-Time... Read more
vPhone, First Smartphone That Can’t Be Lost,...
Austin, Texas based Hypori has introduced the vPhone, a virtual smartphone that affords every business user the benefits of separate work and personal phones, conveniently delivered on a single... Read more
Save this weekend with 2016 refurbished MacBo...
Apple has dropped prices on Certified Refurbished 2016 15″ and 13″ MacBook Pros by as much as $590 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: -... Read more
New 27-inch 3.4GHz iMac on sale for $1699, sa...
MacMall has the new 2017 27″ 3.4GHz iMac (MNE92LL/A) in stock and on sale for $1699 including free shipping. Their price is $100 off MSRP. Read more
Clearance 2016 MacBook Pros available for up...
B&H Photo has clearance 2016 13″ and 15″ MacBook Pros in stock today and on sale for up to $400 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 15″ 2.7GHz... Read more
Apple Ranks 9th In comScore Top 50 U.S. Digit...
comScore, Inc. has released its monthly ranking of U.S. online activity at the top digital media properties for May 2017 based on data from comScore Media Metrix Multi-Platform. * Entity has... Read more
10.5-inch iPad Pros available for up to $20 o...
B&H Photo has the new 2017 10.5″ iPad Pros available for up to $20 off MSRP including free shipping plus NY & NJ sales tax only: - 64GB iPad Pro WiFi: $649 - 256GB iPad Pro WiFi: $749 - 512GB... Read more
Three Off-The-Beaten-Track iOS Apps That Dese...
One of the great things about using iPads and iPhones is the vast selection of apps available for most anything you want or need to do. The three outlined in this article have been in my core app... Read more
Apple No. 1 Spot In Gartner Top 100 Vendors i...
Gartner, Inc. has unveiled the top global 100 vendors in IT in 2016 based on their revenue across IT (excluding communication services) and component market segments. In the Gartner Global Top 100:... Read more
Clearance iMacs available for up to $300 off...
B&H Photo has clearance 21″ and 27″ Apple iMacs available starting at $949, each including free shipping plus NY & NJ sales tax only: - 27″ 3.3GHz iMac 5K: $1999 $300 off original MSRP - 27″... Read more

Jobs Board

*Apple* News Product Marketing Mgr., Publish...
…organizational consensus on strategy and vision for publisher tools, authoring, and Apple News Format.Carries this strategy and vision across the organization to Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject matter Read more
Lead *Apple* Solutions Consultant - Apple I...
…integrity, and trust.Success Metrics/Key Performance Indicators:Quantitative* Year over Year growth in Apple Product and Beyond the Box sales in the assigned Point of Read more
*Apple* Solutions Consultant till v%u00E5r...
…ethics, integrity, and trust.Success Metrics/Key Performance Indicators:QuantitativeYear over Year growth in Apple Product and Beyond the Box sales in the assigned Point Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.