Perl Scripts

This page provides various Perl scripts that I have written over the years. Most of them were written and tested on Mac OS X, and some are specific for OS X, but most should run on any platform where Perl is installed.

File & Folder Management

• copy_without_xattr
  Files on OS X can have resource forks and other extended attributes and as of Tiger (10.4) the 'cp' command copies these extended attributes. This script copies files to a specified destination but suppresses the copying of extended attributes. This is useful when the destination is on a non-HFS volume in order to avoid the "._" files that would otherwise be produced. This Perl script can be conveniently invoked from an AppleScript droplet: copyWithoutXAttr.applescript
• findDupeFiles
  Attempts to identify which files (with a specified suffix) might be duplicates by looking at the MD5 digests. See this macosxhints article for further discussion.
• getFileInfo
  Displays the "creator code" and "type code" of Macintosh files. (See also 'setFileInfo' and 'show_app_creator_code')
• grepl
  Reproduces the functionality of 'grep -l'. (This is useful since there are some patterns that are difficult with 'grep'.) Illustrates how to go on to the next file when using the <> magic to iterate over all lines in all input files.
• listdir
  Lists the files in the specified directory. It gives the info from 'stat' (i.e. similar to 'ls -l')
• listdir_seq
  Lists the files in the specified directory but shows numerical sequences as one item. E.g. the files file1.txt, file2.txt, file3.txt would show as file[1-3].txt (See also 'nextFilename')
• nextFilename
  Displays the name to be used for the next file in a specified directory where the files are named in a numerical sequence. E.g. if the files file1.txt, file2.txt, file3.txt exist, the command 'nextFilename file1.txt' would output "file4.txt". (See also 'listdir_seq')
• peekFile
  Displays the values of the bytes at specified offsets in a specified file. (The name 'peekFile' is supposed to suggest the 'peek' command of BASIC)
• pokeFile
  Edits a binary file by replacing the bytes at specified offsets with the supplied values. (The name 'pokeFile' is supposed to suggest the 'poke' command of BASIC)
• rename_case_colliders
  Renames files where necessary so that the filenames are distinct on case-insensitive filesystems (like HFS+ on OS X)
• rename_for_windows
  Renames files where necessary so that the filenames are acceptable to MS Windows
• rename_without_endspace
  Renames files where necessary to remove leading or trailing whitespace in the filenames
• reportLongPaths
  Reports on files whose full paths are longer than a specified threshold. This is useful when long paths are causing trouble when copying files to some other device. This script illustrates a simple use of the File::Find module.
• resolveAlias
  Resolves a Finder alias.
• setFileInfo
  Sets the "creator code" and "type code" of Macintosh files. (See also 'getFileInfo' and 'show_app_creator_code')
• show_app_creator_code
  Displays the 4 character "creator code" for the specified application
• show_binary
  Displays the contents of files as base 2 numbers
• splitdir
  Splits a (presumably large) directory by moving its files into several sequentially named sub-directories.
• testFileCopy
  Tests the speed of file copying - reports on the read, write, and transfer speeds while copying a file from a specified source to a specified destination. (This is intended for use when troubleshooting slow copying of files from a networked drive for example.) Sample usages are explained in the comments at the top of the script.
• watchdir
  Displays info when a specified directory/folder changes
• watchfile
  Displays info when a specified file changes
• writeToTempFile
  Writes specified text to a temporary file and outputs the name of that file. This illustrates how to write to temp files in a secure way.

Generating Data

• randBytes
  Outputs (to STDOUT) a specified number of random bytes
• sequentialBytes
  Outputs (to STDOUT) a specified number of bytes that cycle from 0..255

Text Processing

• commonStart
  Determines the string that is the common start of a list of strings
• combineCSV
  Combines specified columns from several CSV files into one CSV file. (If you are interested in CSV utilities, see also: csvfix)
• enumerateOccurrences
  Reports on which out of a set of expected values occurred in the specified files
• enumsToPerl
  Creates a Perl module with the info from the 'enum's in a C/C++ header file. Illustrates how to create a module where all the variables are automatically exported.
• letters
  Shows the letters (in alphabetic order) that occur in specified strings.
• permutations
  Prints out all permutations of an array of strings
• report_bad_macros
  Checks on C pre-processor macros and reports macro definitions that are not properly parenthesized
• setOperation
  Performs a set operation (union, intersection, etc) on data from files.
• announceGremlins
  Checks text files for the presence of gremlins. (A "gremlin" is the BBEdit name for an unwanted character, often invisible, that has somehow gotten into your text file.)
• stripHtml
  Outputs the contents of an HTML file after stripping off the HTML tags. Illustrates how to use the HTML::TreeBuilder module.
• usConstitutionSearch
  Search the text of the US constitution (as provided by www.usconstitution.net) for a user-supplied search term and show the matching lines with a few lines of surrounding context. Could easily be modified to search any other text document.

Process Management

• getProcessRss
  Gets the "resident set size" of a specified process. This provides a rough measure of how much RAM that process is using.
• memhogs
  Reports on the top RAM-consuming processes, swap-file usage and pageouts.
• sudoTs
  Reports on the 'sudo' timestamp
• test_signals
  Illustrates the effect of various signals

Networking

• get_wan_ip
  Gets the "external IP address" by extracting it from the HTML returned from a publicly available web site that provides this service.

User Interaction

• ash (AppleScript shell)
  Allows interactive use of AppleScript (like a Unix shell)
• runScriptFromClipboard
  Runs the script (shell script or AppleScript) that is currently that is currently in the Clipboard - i.e. the script text that had previously been copied to the Clipboard. (see also 'runScriptFromWebPage')
• runScriptFromWebPage
  Runs the script (shell script or AppleScript) that is currently selected on the frontmost web page (see also 'runScriptFromClipboard')
• simple_shell
  An example of a very simple "shell" program - intended as an illustration of the basic concepts
• wait_for_keypress
  Illustrates how to wait for a keypress in Perl

Misc

• epochToIsoDate
  Converts epoch time (seconds since January 1, 1970) to a date in ISO 8601 format.
• fifimage
  An example of a named pipe or FIFO. Run this script and then read (e.g. with 'cat') from the fifo and it will read a random jpg file from the image directory. (See also 'logFifo')
• getConsoleUsername
  This script echos the name of the currently active user. (this is useful when using Fast User Switching) This script also serves as an illustration of using the 'scutil' command.
• getDarwinSource
  This script can be used to download the Darwin source code (i.e. the open-source part of OS X) assuming you have an APSL account. It illustrates the use of the Perl "LWP" module.
• ioregValues
  Reports the values of specified properties of an 'ioreg' object. (The 'ioreg' command on OS X displays values of the "I/O Kit registry" which includes a lot of information about the current state of the hardware on an Apple Mac machine.)
• logFifo
  An example of a named pipe or FIFO. Run this script and then write (e.g. with 'echo') to the fifo. Each message sent will be output to STDOUT tagged with the current time. (See also 'fifimage')
• lookieCookies
  Shows info about the cookies that are in a Cookies.plist file
• runEmbeddedScript
  Illustrates how to run an embedded Perl script (source embedded in the current script) as a separate process. The new process (running the embedded Perl script) is completely independent of the parent process. It will continue to run even after the parent dies.
• showLaunchdEnviron
  This script shows the the environment (variables, etc) that is used for scripts run via 'launchd'. It also serves as an illustration of how to run 'launchd' scripts.
• semaphoreMovie
  Text to semaphore converter that creates a QuickTime movie showing the semaphore flag sequence for a given text string. The flag images are derived from those on the above Wikipedia page. Uses the QuickTime command-line tools "qt_tools" to turn a sequence of images into a movie. If you want to run this, get the zip file with semaphoreMovie script and images.
• speakPhonetic
  Speaks text using the NATO Phonetic Alphabet
• test_stderr
  Illustrates how text output can be sent to STDERR as well as STDOUT. This script can be used to test output redirection in shell scripts
• virusChecker
  Purports to check for viruses - but in fact doesn't do anything other than traverse the filesystem while reporting its progress
• writingToFile
  Illustrates how to read and write to files in Perl.
• zero_separated
  Outputs specified strings to STDOUT separated by zeros. This is useful, for example, to generate a spelling dictionary in the format apparently used by OS X's built-in spell checker. (E.g. ~/Library/Spelling/en)

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