TweetFollow Us on Twitter

December 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 (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 character 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. 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 filename 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 character at the end.

  • As discussed in Issue 26, you can use ® (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 ® 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

iDefrag 5.1.7 - Disk defragmentation and...
iDefrag helps defragment and optimize your disk for improved performance. Features include: Supports HFS and HFS+ (Mac OS Extended). Supports case sensitive and journaled filesystems. Supports... Read more
TrailRunner 3.8.832 - Route planning for...
TrailRunner is the perfect companion for runners, bikers, hikers, and all people wandering under the sky. Plan routes on a geographical map. Import GPS or workout recordings and journalize your... Read more
VOX 2.8.14 - 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
WhiteCap 6.6 - Visual plug-in for iTunes...
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
VueScan 9.5.65 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Carbon Copy Cloner 4.1.13 - Easy-to-use...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
TrailRunner 3.8.831 - Route planning for...
TrailRunner is the perfect companion for runners, bikers, hikers, and all people wandering under the sky. Plan routes on a geographical map. Import GPS or workout recordings and journalize your... Read more
Quicken 4.4.2 - Complete personal financ...
Quicken makes managing your money easier than ever. Whether paying bills, upgrading from Windows, enjoying more reliable downloads, or getting expert product help, Quicken's new and improved features... Read more
Adobe Illustrator CC 2017 21.0.2 - Profe...
Illustrator CC 2017 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Illustrator customer). Adobe Illustrator CC 2017 is the industry... Read more
Paparazzi! 1.0b2 - Make user-defined siz...
Paparazzi! is a small utility for OS X that makes screenshots of webpages. This very simple tool takes screenshots of websites which do not fit on one screen. You specify the desired width, minimal... Read more

5 dastardly difficult roguelikes like th...
Edmund McMillen's popular roguelike creation The Binding of Isaac: Rebirth has finally crawled onto mobile devices. It's a grotesque dual-stick shooter that tosses you into an endless, procedurally generated basement as you, the pitiable Isaac,... | Read more »
Last week on PocketGamer
Welcome to a weekly feature looking back on the past seven days of coverage on our sister website, PocketGamer. It’s taken a while for 2017 to really get going, at least when it comes to the world of portable gaming. Thank goodness, then, for... | Read more »
ROME: Total War - Barbarian Invasion set...
To the delight of mobile strategy fans, Feral Interactive released ROME: Total War just a few months ago. Now the game's expansion, Barbarian Invasion is marching onto iPads as a standalone release. [Read more] | Read more »
Yuri (Games)
Yuri 1.0 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: It's night. Yuri opens his eyes. He wakes up in a strange forest.The small, courageous explorer rides on his bed on casters in this... | Read more »
Space schmup Xenoraid launches on the Ap...
10Tons Xenoraid is out today on the App Store, bringing some high-speed space action to your mobile gadgets just in time for the weekend. The company's last premium title, another sci-fi game titled Neon Chrome, did quite well for itself, so... | Read more »
Star Wars: Force Arena Beginner's G...
Star Wars: Force Arena joined the populous ranks of Star Wars games on mobile today. It's a two-lane MOBA starring many familiar faces from George Lucas's famed sci-fi franchise. As with most games of this nature, Force Arena can be a little obtuse... | Read more »
Mysterium: The Board Game (Games)
Mysterium: The Board Game 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: The official adaptation of the famous board game Mysterium! | Read more »
Sonny (Games)
Sonny 1.0.4 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.4 (iTunes) Description: Reimagined for iOS, cult-hit RPG Sonny brings challenging turn-based combat that requires strategy and mastery of each new skill to... | Read more »
Towaga (Games)
Towaga 1.0 Device: iOS iPhone Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: "It has been foretold that a masked being would stand atop the legendary Towaga Temple, dwelling among shadows to fulfil The Black Moon... | Read more »
Bubble Witch 3 Saga Guide: How to get th...
King's bringing its fairytale bubble-popping puzzler back for its 3rd outing in Bubble Witch 3 Saga. If you're familiar with the series, not much has changed here on the surface level, though you'll likely be pleased with the improvements. If you'... | Read more »

Price Scanner via MacPrices.net

Opera Announces Neon Concept Browser For Mac
Opera is inviting users to get a glimpse of what Opera for computers could become with its Opera Neon browser concept. Each Opera Neon feature is described as “an alternate reality” for the Opera... Read more
Tellini Releases TabView 3.0 Missing Tool fo...
Tellini has announced the release of TabView 3.0. TabView has been the first macOS viewer for PowerTab tablatures. PowerTab is a well-known and widely adopted tablature editor for Windows systems and... Read more
13-inch 1.6GHz/128GB MacBook Air on sale for...
Overstock.com has the 1.6GHz/128GB 13″ MacBook Air on sale for $130 off MSRP including free shipping: - 13″ 1.6GHz/128GB MacBook Air (MMGF2LL/A): $869.99 $130 off MSRP Their price is the lowest... Read more
12-inch 32GB Space Gray iPad Pro on sale for...
B&H Photo has 12″ Space Gray 32GB WiFi Apple iPad Pros on sale for $55 off MSRP including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $744.44 $55 off... Read more
9-inch 32GB Space Gray iPad Pro on sale for $...
B&H Photo has the 9.7″ 32GB Space Gray Apple iPad Pro on sale for $549 for a limited time. Shipping is free, and B&H charges NY sales tax only. Read more
Apple iMacs on sale for up to $120 off MSRP,...
B&H Photo has 21″ and 27″ Apple iMacs on sale for up to $120 off MSRP, each including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2199 $100 off MSRP - 27″ 3.2GHz/1TB Fusion iMac... Read more
Apple refurbished Apple TVs available for up...
Apple has Certified Refurbished 32GB and 64GB Apple TVs available for up to $30 off the cost of new models. Apple’s standard one-year warranty is included with each model, and shipping is free: -... Read more
1.4GHz Mac mini, refurbished, available for $...
The Apple Store has Apple Certified Refurbished 1.4GHz Mac minis available for $419. Apple’s one-year warranty is included, and shipping is free. Their price is $80 off MSRP, and it’s the lowest... Read more
16GB iPad Air 2, Apple refurbished, available...
Apple has Certified Refurbished 16GB iPad Air 2s available for $319 including free shipping. A standard Apple one-year is included. Their price is $60 off original MSRP for this model. Read more
Mac Pros on sale for $200 off MSRP, refurbish...
B&H Photo has Mac Pros on sale for $200 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3799, $200... Read more

Jobs Board

*Apple* Retail - Multiple Positions- Crows N...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* & PC Desktop Support Technician...
Apple & PC Desktop Support Technician job in Los Angeles, CA Introduction: We have immediate job openings for several Desktop Support Technicians with one of our 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
*Apple* Premier Retailer - PT Service Specia...
DescriptionSimply Mac is the largest premier retailer for Apple products and solutions. At Simply Mac we are all Apple , all the time. Same products. Same prices. Read more
*Apple* Premier Retailer - Service Manager -...
DescriptionSimply Mac is the largest premier retailer for Apple products and solutions. At Simply Mac we are all Apple , all the time. Same products. Same prices. Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.