TweetFollow Us on Twitter

June 96 - MPW Tips And Tricks: Scripted Text Editing

Mpw Tips And Tricks: Scripted Text Editing

Tim Maroney

The MPW Shell contains a full-strength, high-speed text editor with scripting capabilities. It's nothing to write love letters with, because it's targeted at the ASCII format of compiler source files, but it provides the power to automate complex and repetitive tasks in ASCII text. The key to the system lies in a few editing-related commands, together with its regular expressions and selection expressions.

REGULAR EXPRESSIONS

In the MPW Shell, any search command can take one of two kinds of arguments. The first is a plain string, which matches exactly its contents and nothing else, using a simple character-by-character match. The other is a regular expression, which is a pattern that can be recognized by a finite state machine. You can't parse programming languages with regular expressions, but you can use them to recognize many patterns, including wildcards, repeating sequences, and sets of characters. Regular expressions are bracketed with either slashes or backslashes, for searching forward or backward respectively. So, for instance, the regular expression \wombat\ would search backward from the current location for the string "wombat".

There are about 20 special constructs within regular expressions, all of which are cryptically described when you execute the command line "Help Patterns" within the MPW Shell. I'll mention some of the more useful ones here. The wildcard characters are the question mark (?) and the equivalence symbol (~, Option-X). The question mark matches any one character except the end of a line, while the equivalence symbol matches any number of such characters. For instance, /w?mb~t/ would match "wombat" as well as "wambiklort" and "wymbt", but not "wafkambiliot", nor "wkmb" at the end of a line. Restricted sets of symbols can be given in brackets; for instance, you can search for alphanumeric characters with the pattern [a-zA-Z0-9]. The reverse of a set can be specified with the "not" symbol (~, Option-L); for instance, /[~a-z]/ finds any character except a lowercase letter. The start of a line can be specified with the bullet symbol (*, Option-8) and the end of a line with the infinity symbol ([[infinity]], Option-5).

    These keyboard shortcuts are for American QWERTY keyboards. Other keyboards have different layouts. For instance, on a direct neural interface keyboard, think "blue wildebeest" and raise your right ear to type the bullet symbol.*
Repeating patterns can be specified in three ways. Following any pattern with a plus sign (+) means one or more instances of that pattern; for instance, the regular expression /[0-9]+/ would match any sequence of digits. An optional repeating pattern can be similarly specified with an asterisk (*), which means zero or more repetitions. The rarely seen double angle brackets can be used to specify exactly how many repetitions of a pattern are allowed. They're typed as Option-backslash (<<) and Option-Shift-backslash (>>) and enclose a single number to mean exactly that many repetitions, or two numbers separated by a comma to specify a minimum and maximum number of repetitions, or a single number followed by a comma to mean at least that many repetitions. For instance, the pattern /[a-zA-Z]<<3,7>>/ would find all strings composed of alphabetical characters and from three to seven letters long.

There are a number of ways of "escaping" special characters when you want to look for something that has special meaning within regular expressions, such as a question mark or plus sign. You can escape any character with the lowercase delta ([[partialdiff]], Option-D), or use single or double quotes to escape strings. To find the string "wombat+", for instance, you'd need to escape the plus sign: /wombat[[partialdiff]]+/.

Finally, one of the most useful constructs consists of a tagged regular expression. This allows you to associate a number between 0 and 9 with a pattern that's matched, referring to it later with the "registered" symbol (reg., Option-R) followed by a digit. This is very handy when you're doing replacements. For instance, you can replace any angle-bracketed string with a parenthesized string with the following command, which would turn "<wombat>" into "(wombat)":

Replace /<([~<>]*)reg.1>/ (reg.1)
This searches for any number of characters (except angle brackets) that are between angle brackets, assigns them the number 1, and then replaces the angle brackets with parentheses. Note that the syntax of tagged patterns requires the pattern to be parenthesized.

SELECTION EXPRESSIONS

Many editing commands (such as Replace) can take selection expressions as well as regular expressions. Selection expressions provide more ways to select text than the string matching provided by regular expressions. Common selection expressions include the following:
  • The bullet symbol, meaning the start of a file.

  • The infinity symbol, meaning the end of a file.

  • The current selection, denoted by [[section]] (Option-6). This might have been selected with the mouse or by a Find command. [[section]] by itself indicates the selection in the target window (which I'll explain later), while pathname:[[section]] means the selection in the file indicated by the pathname.

  • A line number, specified simply as a number.

  • The name of a marker, specified by the Mark command.

  • A range between two selection expressions, separated by a colon (:).
The above expressions require no special delimiters (they're not directional like regular expressions). Regular expressions are actually a kind of selection expression and are delimited by slash or backslash characters as usual.

Some character-skipping variants of these options are also provided, such as the position that's one character after the selection, denoted by following a selection expression with an uppercase delta ([[Delta]], Option-J). These are useful in dealing with context; for instance, you may want to select a string when it's followed by another character, but not include the following character in the selection. (An example is given later in the Subword script.) Text emitted by a program like a table generator may be in a known format, such as a columnar arrangement, in which case skipping a certain number of characters will take you to the selection you need.

Again, the MPW Shell will give you a terse summary of selection expressions when you execute the command line "Help Selections". I'm not going to list all the minor variants here, but feel free to while away the hours in rapturous contemplation of their mysteries on your own.

EDITING COMMANDS

The most common editing commands are two that you probably use already: Find and Replace. Dialogs that stand in for these commands are built into the MPW Shell and accessible from the Find menu. You can give any selection expression as a search pattern in either of these dialogs by clicking the Selection Expression radio button instead of the default Literal button. The same commands are the basis of most editing scripts. As tools, Find and Replace take a selection expression as their primary argument. Don't confuse Find and Search! The Search command puts out its results as text, while Find actually changes the selection. In addition, Search takes a pattern -- that is, a regular expression -- while Find takes any selection expression. For example, to go to the start of a file in a script, you could give the command "Find *", but not "Search *".

Find is the basic navigation command in most editing scripts. For instance, you can simulate the Select All command in the Edit menu like so:

Find *:[[infinity]]  # select from start to end of target
The commands File and Open, along with the variables Target and Active, determine the files your scripts will work on. "File" is actually an alias for the real command name, Target. The File command opens a file and makes it the target window -- the window behind the frontmost window. The target window is an important notion in MPW. It exists so that you can use the Worksheet window to type commands that affect another window; since the Worksheet would be in front, the window being affected would need to be behind the Worksheet. During scripting, you may prefer to use the Open command, which opens a file and makes it the frontmost window. The target window is referred to as {Target} in scripts, while the frontmost window is called {Active}. Editing commands work on the target window if you don't specify a window explicitly.

The Line command may also be used for navigation: it selects the numbered line in the target window and then brings that window to the front. You probably know this command already if you use compilers in the MPW Shell, since they put out error messages in this form:

File "gwork.c"; Line 418 # Syntax error
Executing this command takes you to the line in your code where the error was detected.

The Position command returns the current position in the target window, as a line number, a character range, or both. The position could be saved to a variable for later use as follows, using the backquote mechanism to execute a command and insert its output inline:

Set SavedLineNumber `Position -l`
There are dozens of commands pertaining to text editing in the MPW scripting language. Help on all of them is available in the MPW Shell. The usual Macintosh text-editing menu commands are available in the MPW scripting language, including New, Open, Close, Save, Revert, Print, and the standard Edit menu commands.

StreamEdit is a standalone editing tool that's rich and strange enough to deserve its own co-->umn. It's a structured search and replacement language based on the UNIXreg. command sed.

Some simpler standalone editing tools are provided. Sort has a rich function set and can be used for many text-editing tasks. Canon takes a file of search and replace strings and applies them to a file. It's used to automate terminology changes, such as the work that was done to make the Mac OS API use fewer acronyms and abbreviations when the new Inside Macintosh books were written. Translate, like the UNIX command tr, maps characters onto other characters.

Text indentation can be handled with four tools: Adjust, Align, Entab, and Format. Adjust shifts a line to the right or left by a specified number of spaces. Align sets the margin of a range of selected lines to the margin of the first selected line. Entab converts runs of spaces to tabs, and Format sets the column width used for tabs in a text document, as well as other settings like font and size. (These settings are saved in a resource in the file, which many ASCII text editors can recognize.)

Text-editing scripts often create temporary files, split single files into multiple files, and perform other file-related tasks. MPW provides commands to help you manage files. It has commands corresponding to almost all Finder operations, such as Duplicate, Move, Delete, and NewFolder. There are also some specialized file commands: FileDiv splits a file into multiple files based on a byte or line count or on embedded form feed characters inserted during a previous editing pass; Catenate does the opposite, joining files together.

A text-editing script often takes search and substitution text as parameters on the command line. A few commands related to parameters are worth a quick mention here. Echo is handy for concatenating parameters with other text. Quote is similar to Echo but adds quote marks as needed to preserve the word breaks in its parameters. MPW scripting requires quotes around any string that is meant to be a single parameter but contains spaces (which would break the string into multiple parameters). Echo puts out its arguments in a way that allows them to be broken up, while Quote preserves the original word breaks by inserting quotes.

Echo "Richard Loves Pat"
Richard Loves Pat
Quote "Bill Loves Everyone"
'Bill Loves Everyone'

AN EXAMPLE SCRIPT

Here's a script I've found useful for some years. It's called Subword and it replaces a word by another string everywhere it occurs in the target window.
Set Sep "[~a-zA-Z_0-9]"  # word separators
Find * "{Target}"  # start at top of file
Replace -c [[infinity]] [[partialdiff]]
   "[[Delta]]/{Sep}{1}{Sep}/!1:[[Delta]]/{Sep}/" [[partialdiff]]
   "{2}" "{Target}"
The selection in this Replace command is probably about as clear as the U.S. tax code, so allow me to explain. The [[Delta]] means one character before the selection. The !1 means one character past the selection. The colon denotes everything between the selections (inclusively). So this pattern says, in a nutshell, select the pattern in the first parameter ({1}) when it's bracketed by separators, but exclude the separators.

Normally I don't use this script directly. I incorporate it into other scripts as a utility. The bulk of the work of converting between similar languages like Pascal and C can be done by an editing script, for example. Subword can be used to convert keywords, as could Canon. I use another script which is essentially Subword without the separators for changing symbols like equality operators.

Scripts to preconvert between Pascal and C can be found on this issue's CD. They don't generate compiler-ready text, but I've found that they facilitate a manual conversion at the rate of hundreds of lines per hour, allowing source bases in the thousands of lines to be accurately translated in a day or three. So the next time you're faced with a dull text-processing task, look over the tools MPW gives you, and see whether you can save yourself a few days of tedious manual labor!

TIM MARONEY recently changed his Apple badge color from green to white: he's gone from contract programming to a technical leadership role developing user interface software. Tim entertains himself in a variety of ways, such as straining his surgically altered eyeballs on the small print of obscure footnotes and collectible trading card games, and contorting his limbs in yogic asanas. He designed the iron crystal that now resides at the core of the earth and contributed significant ideas to the original (now obsolete) implementation of Planck-scale gravitational phenomena in the universe.*

Thanks to Dave Evans, Scott Fraser, Arno Gourdol, and Alex McKale for reviewing this column.*

 
AAPL
$117.60
Apple Inc.
-1.03
MSFT
$47.47
Microsoft Corpora
-0.12
GOOG
$541.08
Google Inc.
+1.81

MacTech Search:
Community Search:

Software Updates via MacUpdate

MacUpdate Desktop 6.0.3 - Discover and i...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more
SteerMouse 4.2.2 - Powerful third-party...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
iMazing 1.1 - Complete iOS device manage...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
PopChar X 7.0 - Floating window shows av...
PopChar X helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to access any font's special characters. Expanded... Read more
Carbon Copy Cloner 4.0.3 - Easy-to-use b...
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
ForeverSave 2.1.3 - Universal auto-save...
ForeverSave auto-saves all documents you're working on while simultaneously doing backup versioning in the background. Lost data can be quickly restored at any time. Losing data, caused by... Read more
Voila 3.8.1 - Capture, annotate, organiz...
Voila is a screen-capture, recording, and annotation tool that is a full-featured replacement for Mac's screen-capture and screen-recording capabilities. It has a large and robust set of editing,... Read more
SyncTwoFolders 2.0.6 - Syncs two user-sp...
SyncTwoFolders simply synchronizes two folders. It supports synchronization across mounted network drives and it is a possibility to run a simulation showing in a log what will be done. Please visit... Read more
Duplicate Annihilator 5.1.1 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator detects... Read more
HandBrake 0.10.0 - Versatile video encod...
HandBrake is a tool for converting video from nearly any format to a selection of modern, widely supported codecs. Supported Sources: VIDEO_TS folder, DVD image or real DVD (unencrypted -- CSS is... Read more

Latest Forum Discussions

See All

Tilt to Live Bundle Set to Arrive This T...
Tilt to Live Bundle Set to Arrive This Thanksgiving Posted by Ellis Spice on November 25th, 2014 [ permalink ] One Man Left has unveiled an upcoming Tilt to Live bundle, allowing players to get the series for a di | Read more »
BattleLore: Command (Entertainment)
BattleLore: Command 1.0 Device: iOS Universal Category: Entertainment Price: $9.99, Version: 1.0 (iTunes) Description: ***NOTE: Compatible with iPad 2/iPad mini, iPod touch 5 and up and iPhone 4S and up – WILL NOT RUN ON EARLIER... | Read more »
Weather Or Not Review
Weather Or Not Review By Jennifer Allen on November 25th, 2014 Our Rating: :: STYLISH WEATHER REPORTINGiPhone App - Designed for the iPhone, compatible with the iPad Check the weather quickly and conveniently with Weather or Not... | Read more »
The All-New Football Manager Handheld 20...
The All-New Football Manager Handheld 2015 is Available Now Posted by Jessica Fisher on November 25th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Six iOS Games to Get You Ready for Thank...
Image Source: Friends Wiki At this point in the month, you or at least a few people you know are probably getting ready to scramble around (or are already scrambling around) for Thanksgiving Dinner. It’s a hectic day of precise oven utilization, but... | Read more »
Call of Duty: Heroes: Tips, Tricks, and...
Hello Heroes: What’d we think of Call of Duty‘s take on Clash of Clans? Check out our Call of Duty: Heroes review to find out! Just downloaded Call of Duty: Heroes and need some handy tips and tricks on how to get ahead of the rest? As we often do,... | Read more »
Call of Duty: Heroes Review
Call of Duty: Heroes Review By Jennifer Allen on November 25th, 2014 Our Rating: :: CLASH OF FRANCHISESUniversal App - Designed for iPhone and iPad Mix Clash of Clans with Call of Duty, and this is what you get.   | Read more »
Slider Review
Slider Review By Jordan Minor on November 25th, 2014 Our Rating: :: SLIDE TO PLAYUniversal App - Designed for iPhone and iPad Slider has all the excitement of unlocking your phone screen.   | Read more »
oh my giraffe (Games)
oh my giraffe 1.0.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.0 (iTunes) Description: Eat fruits while being chased by lions. Cut the vines to send fruit plummeting onto the lions. Don't worry, your flexible... | Read more »
One of 2000’s Most Loves Adventure Games...
One of 2000’s Most Loves Adventure Games, The Longest Journey, has Come to iOS Posted by Jessica Fisher on November 25th, 2014 [ permalink ] | Read more »

Price Scanner via MacPrices.net

Early Black Friday MacBook Pro sale: 15-inch...
 Best Buy has posted early Black Friday prices on 15″ Retina MacBook Pros, with models on sale for $300 off MSRP on their online store for a limited time. Choose free local store pickup (if available... Read more
A9 Chips Already?
It’s barely more than a couple of months since Apple got the first A8 systems-on-chip into consumer hands, but rumor and news focus is already turning to the next-generation A9 SoC. Apple Daily... Read more
NewerTech Announces NuGuard KXs Impact X-Orbi...
NewerTech has announced updates to its family of Impact X-Orbing Screen Armor bringing military grade, triple layer protection to Apple’s new iPhone 6 and 6 Plus. Like all models in the NuGuard KXs... Read more
13-inch 1.4GHz MacBook Air on sale for $889,...
 B&H Photo has the 13″ 1.4GHz/128GB MacBook Air on sale for $889 including free shipping plus NY tax only. Their price is $110 off MSRP. B&H will also include free copies of Parallels Desktop... Read more
Save up to $300 on Macs and iPads with your A...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
Apple refurbished Mac Pros available for up t...
The Apple Store is offering Apple Certified Refurbished Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
Jumptuit Launches One-Tap Windows 8.1 iTunes...
Jumptuit has launched Windows 8.1 support for One-Tap iTunes Sync. with which Windows 8.1 users can now easily sync their iTunes libraries with Microsoft OneDrive. Jumptuit provides easy access from... Read more
Apple restocks refurbished 13-inch 2014 Retin...
The Apple Store has restocked Apple Certified Refurbished 2014 13″ 2.6GHz Retina MacBook Pros for up to $230 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
CEA Study Finds More People Recycling Electro...
A new study by the Consumer Electronics Association (CEA) finds that electronics recycling receives the continued and growing support of consumers. According to the CEA,s Recycling and Reuse Study,... Read more
15″ 2.2GHz Retina MacBook Pro on sale for $17...
 B&H Photo has the 2014 15″ 2.2GHz Retina MacBook Pro on sale today for $1749. Shipping is free, and B&H charges NY sales tax only. B&H will also include free copies of Parallels Desktop... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC)- Retail S...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.