How do I use Ruby for shell scripting

Question

I have some simple shell scripting tasks that I want to do     For example  Selecting a file in the working directory from a list of the files matching some regular expression   I know that I can do this sort of thing using standard bash and grep but I would be nice to be able to hack quick scripts that will work in windows and linux without me having to memorize a heap of command line programs and flags etc   I tried to get this going but ended up getting confused about where I should be getting information such as a reference to the current directory  So the question is what parts of the Ruby libraries do I need to know to write ruby shell scripts

User · Accepted Answer

By default  you already have access to Dir and File  which are pretty useful by themselves   Dir    rb    basic globs Dir       rb          any depth of directory  including current dir     gt  array of relative names  File expand path    file txt      gt    User mat file txt  File dirname  dir file txt      gt   dir  File basename  dir file txt      gt   file txt  File join  a    bunch    of    strings      gt   a bunch of strings     FILE      gt  the name of the current file   Also useful from the stdlib is FileUtils  require  fileutils   I know  no underscore is not ruby-like include FileUtils   Gives you access  without prepending by  FileUtils    to cd dir  options  cd dir  options    dir         pwd   mkdir dir  options  mkdir list  options  mkdir p dir  options  mkdir p list  options  rmdir dir  options  rmdir list  options  ln old  new  options  ln list  destdir  options  ln s old  new  options  ln s list  destdir  options  ln sf src  dest  options  cp src  dest  options  cp list  dir  options  cp r src  dest  options  cp r list  dir  options  mv src  dest  options  mv list  dir  options  rm list  options  rm r list  options  rm rf list  options  install src  dest  mode    lt src s gt   options  chmod mode  list  options  chmod R mode  list  options  chown user  group  list  options  chown R user  group  list  options  touch list  options    Which is pretty nice

User · Answer

How do I write ruby  is a little beyond the scope of SO   But to turn these ruby scripts into executable scripts  put this as the first line of your ruby script      path to ruby   Then make the file executable   chmod a x myscript rb   and away you go

User · Answer

As the others have said already  your first line should be     usr bin env ruby   And you also have to make it executable   in the shell   chmod  x test rb   Then follows the ruby code  If you open a file  File open  file    r   do  io        do something with io end   the file is opened in the current directory you d get with pwd in the shell   The path to your script is also simple to get  With  0 you get the first argument of the shell  which is the relative path to your script  The absolute path can be determined like that      usr bin env ruby require  pathname  p Pathname new  0  realpath     For file system operations I almost always use Pathname  This is a wrapper for many of the other file system related classes  Also useful  Dir  File

User · Answer

This might also be helpful  http   rush heroku com   I haven t used it much  but looks pretty cool  From the site      rush is a replacement for the unix shell  bash  zsh  etc  which uses pure Ruby syntax  Grep through files  find and kill processes  copy files - everything you do in the shell  now in Ruby

User · Answer

This might also be helpful  http   rush heroku com   I haven t used it much  but looks pretty cool  From the site      rush is a replacement for the unix shell  bash  zsh  etc  which uses pure Ruby syntax  Grep through files  find and kill processes  copy files - everything you do in the shell  now in Ruby

User · Answer

Here s something important that s missing from the other answers  the command-line parameters are exposed to your Ruby shell script through the ARGV  global  array   So  if you had a script called my shell script      usr bin env ruby puts  I was passed    ARGV each do  value    puts value end      make it executable  as others have mentioned    chmod u x my shell script   And call it like so      gt    my shell script one two three four five   You d get this   I was passed   one two three four five   The arguments work nicely with filename expansion     my shell script    I was passed   a file in the current directory another file     my shell script the last file   Most of this only works on UNIX  Linux  Mac OS X   but you can do similar  though less convenient  things in Windows

User · Answer

Go get yourself a copy of Everyday Scripting with Ruby   It has plenty of useful tips on how to do the types of things your are wanting to do

User · Answer

Place this at the beginning of your script rb     usr bin env ruby   Then mark it as executable   chmod  x script rb

User · Answer

The answer by webmat is perfect  I just want to point you to a addition  If you have to deal a lot with command line parameters for your scripts  you should use optparse  It is simple and helps you tremendously

User · Answer

In ruby  the constant   FILE   will always give you the path of the script you re running   On Linux   usr bin env is your friend       usr bin env ruby   Extension of this script does not matter as long   as it is executable  chmod  x  puts File expand path   FILE      On Windows it depends whether or not  rb files are associated with ruby  If they are     This script filename must end with  rb puts File expand path   FILE      If they are not  you have to explicitly invoke ruby on them  I use a intermediate  cmd file   my script cmd    ruby   dp0 my script rb   my script rb   puts File expand path   FILE

User · Answer

There s a lot of good advice here  so I wanted to add a tiny bit more    Backticks  or back-ticks  let you do some scripting stuff a lot easier  Consider  puts  find     grep -i lib   If you run into problems with getting the output of backticks  the stuff is going to standard err instead of standard out  Use this advice  out    git status 2 gt  amp 1   Backticks do string interpolation   blah    lib   touch   blah    You can pipe inside Ruby  too  It s a link to my blog  but it links back here so it s okay    There are probably more advanced things out there on this topic  As other people noted  if you want to get serious there is Rush  not just as a shell replacement  which is a bit too zany for me  but also as a library for your use in shell scripts and programs      On Mac  Use Applescript inside Ruby for more power  Here s my shell here script      usr bin env ruby  env   pbcopy   cmd     Q tell app  Terminal  to do script    paste env    puts cmd   osascript -e    cmd

User · Answer

The above answer are interesting and very helpful when using Ruby as shell script  For me  I does not use Ruby as my daily language and I prefer to use ruby as flow control only and still use bash to do the tasks   Some helper function can be used for testing execution result     usr bin env ruby module ShellHelper   def test command         command  2 gt   dev null         success    end    def execute command  raise on error   true      result      command       raise  execute command failed n  if  not    success   and raise on error     return    success    end    def print exit message      print    message  n      exit   end    module function  execute   print exit   test end   With helper  the ruby script could be bash alike      usr bin env ruby require    shell helper  include ShellHelper  print exit  config already exists  if test  ls config   things each do  thing    next if not test  ls   thing  config    execute  cp -fr   thing  config template config   thing   end

User · Answer

let s say you write your script rb script  put      usr bin env ruby   as the first line and do a chmod  x script rb

User · Answer

When you want to write more complex ruby scripts  these tools may help   For example     thor a scripting framework  gli git like interface  methadone for creating simple tools    They give you a quick start to write your own scripts  especially  command line app

[ruby] How do I use Ruby for shell scripting?

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