10.12.2020

Regex For Mac Os X

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Regex for Mac OS X is a powerful regular expressions editor that dynamically highlight matches. Available for: macOS Sierra 10.12.4, OS X El Capitan 10.11.6, and OS X Yosemite 10.10.5. Impact: An application may be able to escape its sandbox. Description: A memory corruption issue was addressed with improved memory handling. CVE-2017-2512: Federico Bento of Faculty of Sciences, University of Porto.

First off, regex is shorthand for a regular expression. And what, exactly, is a regular expression? According to the linked Wikipedia page, a regular expression is…

…in theoretical computer science and formal language theory, a sequence of characters that define a search pattern. Usually this pattern is then used by string searching algorithms for 'find' or 'find and replace' operations on strings.

That's a mouthful, but what it means is that you can write some really bizarre looking code that will transform text from one form to another form. And if you know just a bit of regex, and where to go to look up what you don't know, then you can use regex to do many useful things.

For example, consider this filename on a scanned-to-PDF receipt:

The Party Place [party supplies] - 02-06-2017

Perhaps you'd prefer it if the date came first, in year-month-day order, so that your receipts were ordered by date, like this:

2017-02-06 - The Party Place [party supplies]

Sure, you could manually rename this one file, but what if you have 500 receipts that you need to rename? Enter regular expressions—they'll let you do this text manipulation, and many more. What follows is a very brief summary of my knowledge of regex, along with pointers to sites where I go when (very often) the problem I need to solve is beyond my regex skill level.

First off, where can you use regex? In many places; in my case, my need to learn some regex came from our own app Name Mangler, which supports it in renaming operations. I also use regex in BBEdit (and the free TextWrangler), where it's available via a 'grep' checkbox in the Find dialog.

In addition, you can use regex with any numer of Terminal programs, including sed, awk, perl, and ruby.

While the syntax may be somewhat…OK, incredibly…obtuse, there's no doubt that knowing some regex can help you manipulate text in ways that would otherwise be really time consuming. Consider the filename example from above; you can rearrange the filename into the preferred order with these regex structures:

Find: (.*) - ([d]{2})-([d]{2})-([d]{4})
Replace: $4-$2-$3 - $1

Just how exactly does all that gibberish work to transform a filename? Follow me now as I attempt to break it down into plain language; regex pros, please note that I'm sure I'll get some of this wrong, so feel free to correct me.

A regex generally proceeds through the text from left to right (there are ways to find relative to the end), so let's look at each piece of the find structure in that order.

(.*)

First, about those parentheses. A set of parentheses in regex means 'put whatever matches the regex inside the parentheses into a variable for future use (typically in the 'replace' step).' The variables are assigned in order, with the first set of parentheses becoming $1, the next $2, etc.

The .* says to match any character (the dot) zero or more times (the star). This literally means 'match anything, and put it in $1.' You might think you'd wind up with the entire filename in $1, and you'd be right…except there's more regex that limits what it matches…

-

This bit finds the 'space hyphen space' (I've colored the spaces gray so you can see them) that separates the name from the date in the original filename. This also limits the first bit of the regex's 'match anything' structure: It will match anything up to the 'space hyphen space.' So we wind up with the text of the filename in $1, not the entire string.

There are no parentheses around this part because I don't need to keep it; I just need to find it so I can then move on to the next part of the filename.

Note: To get ultra-geeky for a sec, this bit is written in Name Mangler's syntax, which is based on PCRE in free-spacing mode, which requires spaces to be escaped—hence the backslashes around the two spaces in the string. Other forms of regex don't require the spaces to be escaped.

([d]{2})-

Another set of parentheses, so these results will become $2. The [d] is a shorthand character class which means 'a digit between 0 and 9.' The {2} says 'find two of the previous thing in a row,' that is, two digits. Finally, the trailing - is the hyphen that separates the month from the day—it's not in the parentheses because I don't need to keep it. The net result of this step is that the month is stored in $2.

([d]{2})-

Identical to the previous bit, except that this will be stored in $3, as it's the third set of parentheses. This pulls the day out and stores it, again dropping the hyphen.

([d]{4})

This is very similar to the previous two steps, but now, we find four digits—the year—and it gets stored in $4.

So after executing this find, we have four variables with these values:

$1 - The Party Place [party supplies]
$2 - 02
$3 - 06
$4 - 2017

With those values in the variables, the replace bit is now relatively self-explanatory:

$4-$2-$3 - $1

Year first, then month, day, and filename, with hyphens and spaces inserted where needed. As you can see, regex can do some powerful manipulation on strings, whether those strings are in a file or are a series of filenames. I've only scratched the surface here, because honestly, that's about how deep my knowledge goes.

When I reach my regex knowledge limits, here are the sites where I go for more help.

Regular-Expressions.info

This is the 'big one,' a massive site with tons of detail on everything regex. There are examples, definitions, rules, exceptiopns, and so much more. It's not a light read, but when I'm stuck, I can almost always find what I'm looking for here.

The Wikipedia regex page

There's not as much detail here, but there are some nice tables showing syntax for various regex constructs. There's also a brief history of regex, if such things interest you

Online regex tester

I use this site—therearemanyothers—to test my regex builds against the text I want them to act on. As a relative regex neophyte, I spend a lot of time on this site, checking my expressions before putting them to use.

It has a couple nice features that I really find useful. First, if you hover over your regex, pop-ups explain what each little section does (this also works when hovering over the replacement regex):

Second, if you hover over the test string, a pop-up shows exactly what your regex has captured:

There may be other sites that do this, too, but this is the first one I found, and I stopped looking at that point.

MSDN regex quick reference

Microsoft's developer site has a nice regex reference, with lots of easy-to-read tables explaining various regex constructs.

4.1. Getting and Installing MacPython¶

Mac OS X 10.8 comes with Python 2.7 pre-installed by Apple. If you wish, youare invited to install the most recent version of Python 3 from the Pythonwebsite (https://www.python.org). A current “universal binary” build of Python,which runs natively on the Mac’s new Intel and legacy PPC CPU’s, is availablethere.

What you get after installing is a number of things:

A Python3.8 folder in your Applications folder. In hereyou find IDLE, the development environment that is a standard part of officialPython distributions; and PythonLauncher, which handles double-clicking Pythonscripts from the Finder.
A framework /Library/Frameworks/Python.framework, which includes thePython executable and libraries. The installer adds this location to your shellpath. To uninstall MacPython, you can simply remove these three things. Asymlink to the Python executable is placed in /usr/local/bin/.

The Apple-provided build of Python is installed in/System/Library/Frameworks/Python.framework and /usr/bin/python,respectively. You should never modify or delete these, as they areApple-controlled and are used by Apple- or third-party software. Remember thatif you choose to install a newer Python version from python.org, you will havetwo different but functional Python installations on your computer, so it willbe important that your paths and usages are consistent with what you want to do.

IDLE includes a help menu that allows you to access Python documentation. If youare completely new to Python you should start reading the tutorial introductionin that document.

If you are familiar with Python on other Unix platforms you should read thesection on running Python scripts from the Unix shell.

4.1.1. How to run a Python script¶

Your best way to get started with Python on Mac OS X is through the IDLEintegrated development environment, see section The IDE and use the Help menuwhen the IDE is running.

If you want to run Python scripts from the Terminal window command line or fromthe Finder you first need an editor to create your script. Mac OS X comes with anumber of standard Unix command line editors, vim andemacs among them. If you want a more Mac-like editor,BBEdit or TextWrangler from Bare Bones Software (seehttp://www.barebones.com/products/bbedit/index.html) are good choices, as isTextMate (see https://macromates.com/). Other editors includeGvim (http://macvim-dev.github.io/macvim/) and Aquamacs(http://aquamacs.org/).

To run your script from the Terminal window you must make sure that/usr/local/bin is in your shell search path.

To run your script from the Finder you have two options:

Drag it to PythonLauncher
Select PythonLauncher as the default application to open yourscript (or any .py script) through the finder Info window and double-click it.PythonLauncher has various preferences to control how your script islaunched. Option-dragging allows you to change these for one invocation, or useits Preferences menu to change things globally.

4.1.2. Running scripts with a GUI¶

With older versions of Python, there is one Mac OS X quirk that you need to beaware of: programs that talk to the Aqua window manager (in other words,anything that has a GUI) need to be run in a special way. Use pythonwinstead of python to start such scripts.

With Python 3.8, you can use either python or pythonw.

4.1.3. Configuration¶

Python on OS X honors all standard Unix environment variables such asPYTHONPATH, but setting these variables for programs started from theFinder is non-standard as the Finder does not read your .profile or.cshrc at startup. You need to create a file~/.MacOSX/environment.plist. See Apple’s Technical Document QA1067 fordetails.

For more information on installation Python packages in MacPython, see sectionInstalling Additional Python Packages.

4.2. The IDE¶

MacPython ships with the standard IDLE development environment. A goodintroduction to using IDLE can be found athttp://www.hashcollision.org/hkn/python/idle_intro/index.html.

4.3. Installing Additional Python Packages¶

There are several methods to install additional Python packages:

Packages can be installed via the standard Python distutils mode (pythonsetup.pyinstall).
Many packages can also be installed via the setuptools extensionor pip wrapper, see https://pip.pypa.io/.

4.4. GUI Programming on the Mac¶

There are several options for building GUI applications on the Mac with Python.

Regular Expression Mac Os X

PyObjC is a Python binding to Apple’s Objective-C/Cocoa framework, which isthe foundation of most modern Mac development. Information on PyObjC isavailable from https://pypi.org/project/pyobjc/.

The standard Python GUI toolkit is tkinter, based on the cross-platformTk toolkit (https://www.tcl.tk). An Aqua-native version of Tk is bundled with OSX by Apple, and the latest version can be downloaded and installed fromhttps://www.activestate.com; it can also be built from source.

wxPython is another popular cross-platform GUI toolkit that runs natively onMac OS X. Packages and documentation are available from https://www.wxpython.org.

PyQt is another popular cross-platform GUI toolkit that runs natively on MacOS X. More information can be found athttps://riverbankcomputing.com/software/pyqt/intro.

4.5. Distributing Python Applications on the Mac¶

The standard tool for deploying standalone Python applications on the Mac ispy2app. More information on installing and using py2app can be foundat http://undefined.org/python/#py2app.

Regex For Mac Os X 10 13 Download

4.6. Other Resources¶

The MacPython mailing list is an excellent support resource for Python users anddevelopers on the Mac:

Mac Os X 10.11 Download Free

Another useful resource is the MacPython wiki:

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