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

Boom 2 1.0.1 - System-wide pro audio app...
Boom 2 is a system-wide volume booster and equalizer app that is designed especially for OS X 10.10 Yosemite. It comes with a smart interface, self-calibrates itself according to your Mac, offers... Read more
Apple Security Update 2015-001 - For OS...
Apple Security Update 2015-001 is recommended for all users and improves the security of OS X. For detailed information about the security content of this update, please visit: http://support.apple.... Read more
Drive Genius 4.0.1 - Powerful system uti...
Drive Genius 4 gives you faster performance from your Mac while also protecting it. The award-winning and improved DrivePulse feature alerts you to hard drive issues before they become major problems... Read more
Yosemite Cache Cleaner 9.0.3 - Clear cac...
Yosemite Cache Cleaner is an award-winning general purpose tool for OS X. YCC makes system maintenance simple with an easy point-and-click interface to many OS X functions. Novice and expert users... Read more
xScope 4.1.1 - Onscreen graphic measurem...
xScope is powerful set of tools that are ideal for measuring, inspecting, and testing on-screen graphics and layouts. Its tools float above your desktop windows and can be accessed via a toolbar,... Read more
OS X Yosemite 10.10.2 - Apple's lat...
OS X Yosemite is Apple's newest operating system for Mac. An elegant design that feels entirely fresh, yet inherently familiar. The apps you use every day, enhanced with new features. And a... Read more
Apple iOS 8.1.3 - The latest version of...
The latest version of iOS can be downloaded through iTunes. Apple iOS 8 comes with big updates to apps you use every day, like Messages and Photos. A whole new way to share content with your family.... Read more
SpamSieve 2.9.19 - Robust spam filter fo...
SpamSieve is a robust spam filter for major email clients that uses powerful Bayesian spam filtering. SpamSieve understands what your spam looks like in order to block it all, but also learns what... Read more
RapidWeaver 6.0.5 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
Duet 1.2.2 - Use your iPad as an externa...
Duet is the first app that allows you to use your iDevice as an extra display for your Mac using the Lightning or 30-pin cable. Note: This app requires a $14.99 iOS companion app. Version 1.2.2:... Read more

Storm & Skye – Magical Adventure Sto...
Storm & Skye – Magical Adventure Story For Kids Review By Amy Solomon on January 28th, 2015 Our Rating: iPhone App - Designed for the iPhone, compatible with the iPad The first book in the Storm & Skye series includes... | Read more »
New WOTA: U-Boat Compass ‘Wets’ Your App...
New WOTA: U-Boat Compass ‘Wets’ Your Appetite for WOTA: Wolves of the Atlantic. Posted by Jessica Fisher on January 27th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Warship Solitaire Review
Warship Solitaire Review By Nadia Oxford on January 27th, 2015 Our Rating: :: A WAR OF NUMBERSUniversal App - Designed for iPhone and iPad Warship Solitaire might lack frills and looks, but it offers some thought provoking... | Read more »
Keep Track of Your Hectic Work Schedule...
Keep Track of Your Hectic Work Schedule With Shifts Posted by Jessica Fisher on January 27th, 2015 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
All Star Quarterback Review
All Star Quarterback Review By Campbell Bird on January 27th, 2015 Our Rating: :: PLAY YOUR PARTUniversal App - Designed for iPhone and iPad Train your way to the Super Bowl in this free-to-play sports management game.   | Read more »
Sentinel 4: Dark Star Adds New Campaign...
Sentinel 4: Dark Star Adds New Campaign and More Posted by Ellis Spice on January 27th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Wheel & Deal Review
Wheel & Deal Review By Tre Lawrence on January 27th, 2015 Our Rating: :: SIMPLE FUNUniversal App - Designed for iPhone and iPad A simple arcade shooter that has a retro feel.   | Read more »
Join the NAVY in a Big New Update for WW...
Join the NAVY in a Big New Update for WW2: Sandbox. Strategy & Tactics Posted by Jessica Fisher on January 27th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Earthworm Alchemy Review
Earthworm Alchemy Review By Campbell Bird on January 27th, 2015 Our Rating: :: FEED THE WORMUniversal App - Designed for iPhone and iPad Feed this funny looking worm and dodge bombs in this charming, free-to-play arcade game.   | Read more »
Graphic Novel App netwars – The Butterfl...
Graphic Novel App netwars – The Butterfly Attack has Received Some New Episodes Posted by Jessica Fisher on January 27th, 2015 [ permalink ] | Read more »

Price Scanner via MacPrices.net

15-inch 2.0GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished previous-generation 15″ 2.0GHz Retina MacBook Pros available for $1489 including free shipping plus Apple’s standard one-year warranty. Their price is... Read more
15-inch 2.5GHz Retina MacBook Pro on sale for...
Amazon has the 15″ 2.5GHz Retina MacBook Pro on sale for $2319.99 including free shipping. Their price is $180 off MSRP, and it’s the lowest price available for this model from any reseller. Read more
iPad Turns Five – The ”Book Mystique
Five years ago this week, the late Steve Jobs took the stage at an Apple special press event to unveil the first Apple iPad — a slab-shaped, hand-holdable device that was to shake the personal... Read more
Sale! 15-inch Retina MacBook Pros for up to $...
B&H Photo has the new 2014 15″ Retina MacBook Pros on sale for $150 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1889.99... Read more
Apple refurbished Mac minis for up to $150 of...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
Apple Releases New Tranche Of OS Updates For...
Apple has released incremental bugfix and security updates for its most recent Mac and iOS versions. OS X Yosemite 10.10.2 Update Apple says this update includes the following improvements: Resolves... Read more
Samsung To Be Main Supplier Of A9 Chips For i...
Korea’s Maeil Business Newspaper reports that Samsung has beat out its chipmaking rivals, Taiwan’s Qualcomm and TSMC, as supplier of chipsets for the next generations of both its own Galaxy S6 and... Read more
Save up to $340 on iMacs with Apple Certified...
The Apple Store has Apple Certified Refurbished iMacs available for up to $340 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more
AppleCare Protection Plans on sale for up to...
B&H Photo has 3-Year AppleCare Warranties on sale for up to $105 off MSRP including free shipping plus NY sales tax only: - Mac Laptops 15″ and Above: $244 $105 off MSRP - Mac Laptops 13″ and... Read more
Apple refurbished Time Capsules available sta...
The Apple Store has certified refurbished Time Capsules available for up to $60 off MSRP. Apple’s one-year warranty is included with each Time Capsule, and shipping is free: - 2TB Time Capsule: $255... Read more

Jobs Board

*Apple* Solutions Consultant - Retail Sales...
As an ambassador of the Apple brand, the ASC is accountable for driving sales performance by: Connecting with customers. Discovering customers' needs and values. Showing Read more
*Apple* Solutions Consultant - Retail Sales...
As an ambassador of the Apple brand, the ASC is accountable for driving sales performance by: Connecting with customers. Discovering customers' needs and values. Showing Read more
*Apple* Tree Children's Center is hirin...
Apple Tree Learning Center is Hiring Preschool Teachers! Phoenix Childrens Academy is a national leader in the early childhood education industry and we are currently Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Solutions Consultant - Retail Sales...
As an ambassador of the Apple brand, the ASC is accountable for driving sales performance by: Connecting with customers. Discovering customers' needs and values. Showing Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.