Ruby is part of the default install of OS X.
Working with Ruby gems
Gems are Ruby packages that can be installed to extend the language or provide additional functions. Gems are managed using the
gem command. To find all Ruby gems (packages) currently installed:
To install a new gem:
gem install package
To update the gems package manager:
For untrusted scripts, add -T flag to ruby at the start of the script:
One liner to edit a file in place
This command edits a file in place, performing a global text search/replace. The -p switch tells ruby to place your code in the loop
while gets; ...; print; end. The -i tells ruby to edit files in place, and -e indicates that a one line program follows.
ruby -p -i -e '$_.gsub!(/248/,"949")' file.txt
One liner to remove DOS line endings from a file
A Unix or Mac text file uses a single line feed character to mark the end of a line (hex 0A). Files created on DOS or Windows use two characters, carriage return and line feed (hex 0D 0A). This command edits a file in place, removing the carriage returns.
ruby -p -i -e '$_.gsub!(/\x0D/,"")' file.txt
One liner to edit files in place and backup each one to *.old
ruby -p -i.old -e '$_.gsub!(/248/,"949")' *.txt