Run Ruby, Run!

There is a one-liner on the internet that will start a local web server, for serving all the static files in your current directory:

$ python -m SimpleHTTPServer 8080

Or with Python 3:

$ python3 -m http.server

Rubyists generally do not want to rely on Python, so there is a Ruby equivalent:

$ ruby -run -e httpd . -p 8080

This will fire up a very simple server, written in Ruby, using WEBrick under the hood!

It also takes some more options, see at bottom of this post for a listing of available ones.

Please note: WEBrick was removed from Ruby in version 3.0

How does this work and what does it do exactly? First of all, what does ruby -run mean? The answer might be surprising: It could be rewritten as:

$ ruby -require "un" -e "httpd" . -p 8080

The -e option directly executes the ruby code given, and -r is the short version of --require. So it requires "un", which happens to be included in Ruby's standard library¹. It was written by Hirofumi WATANABE (eban), a long-time Ruby contributor and code golf star. un.rbs goal is to provide:

# Utilities to replace common UNIX commands in Makefiles etc

¹ The same is possible for requiring rubygems

Let's see, what else is included:

#   ruby -run -e cp             -- [OPTION] SOURCE DEST
#   ruby -run -e ln             -- [OPTION] TARGET LINK_NAME
#   ruby -run -e mv             -- [OPTION] SOURCE DEST
#   ruby -run -e rm             -- [OPTION] FILE
#   ruby -run -e mkdir          -- [OPTION] DIRS
#   ruby -run -e rmdir          -- [OPTION] DIRS
#   ruby -run -e install        -- [OPTION] SOURCE DEST
#   ruby -run -e chmod          -- [OPTION] OCTAL-MODE FILE
#   ruby -run -e touch          -- [OPTION] FILE
#   ruby -run -e wait_writable  -- [OPTION] FILE
#   ruby -run -e mkmf           -- [OPTION] EXTNAME [OPTION]
#   ruby -run -e httpd          -- [OPTION] DocumentRoot
#   ruby -run -e help [COMMAND]

Besides httpd, you mostly get FileUtils based implementations of common unix tools,: cp, ln, mv, rm, mkdir, rmdir, install, chmod, and touch.

There are two more commands included, which don't fit into this unix category: mkmf, which you can use to create the Makefile for a Ruby C extension and wait_writable, which allows you to continuously try to open a file in writable mode.

-run Reference

What follows is a reference of all un commands. Also checkout the integrated help with:

$ ruby -run -e help COMMAND

Copy Files

$ ruby -run -e cp SOURCE DEST [OPTIONS]
Argument Description
SOURCE File to copy
DEST Where to copy the file
Option Description
-p Preserve file attributes if possible
-r Copy directories recursively
-v Verbose mode (print executed shell command) 
$ ruby -run -e ln TARGET LINK_NAME [OPTIONS]
Argument Description
TARGET File to create symlink from
LINK_NAME Where to create the symlink
Option Description
-s Make symbolic links instead of hard links
-f Overwrite files, which already exists at destination
-v Verbose mode (print executed shell command)

Move File

$ ruby -run -e mv SOURCE DEST [OPTIONS]
Argument Description
SOURCE File to move
DEST Where to move the file
Option Description
-v Verbose mode (print executed shell command)

Remove File

$ ruby -run -e rm FILE [OPTIONS]
Argument Description
FILE File(s) to remove
Option Description
-f Do nothing if file does not exist
-r Remove the contents of directories recursively
-v Verbose mode (print executed shell command)

Create Directory

$ ruby -run -e mkdir DIRS [OPTIONS]
Argument Description
DIRS Director(y/ies) to create
Option Description
-p Don't fail if directory already exists
Create all directories necessary
-v Verbose mode (print executed shell command)

Remove Directory

$ ruby -run -e rmdir DIRS [OPTIONS]
Argument Description
DIRS Director(y/ies) to remove
Option Description
-p Also remove directory's ancestors
-v Verbose mode (print executed shell command)

Copy Files and Set Attributes

$ ruby -run -e install SOURCE DEST [OPTIONS]
Argument Description
SOURCE File to copy
DEST Where to copy the file
Option Description
-p Apply access/modification times of SOURCE files to
  corresponding destination files
-m Set permission mode (as in chmod), instead of 0755
-v Verbose mode (print executed shell command)

Change File Mode

$ ruby -run -e chmod OCTAL-MODE FILE [OPTIONS]
Argument Description
OCTAL-MODE File mode to set as octal number
FILE File(s) to operate on
Option Description
-v Verbose mode (print executed shell command)

Update File Timestamp or Create Empty File

$ ruby -run -e touch FILE [OPTIONS]
Argument Description
FILE File(s) to touch
Option Description
-v Verbose mode (print executed shell command)

Wait until File gets Writable

$ ruby -run -e wait_writable FILE [OPTIONS]
Argument Description
FILE File(s) to wait for
Option Description
-n RETRY Count how often to retry
-w SEC Time to wait between retries (in seconds)
-v Verbose mode (print access errors)

Make Makefile

$ ruby -run -e mkmf EXTNAME [OPTIONS]
Argument Description
EXTNAME Extension name
Option Description
-d ARGS Run dir_config
-h ARGS Run have_header
-l ARGS Run have_library
-f ARGS Run have_func
-v ARGS Run have_var
-t ARGS Run have_type
-m ARGS Run have_macro
-c ARGS Run have_const
–vendor Install to vendor_ruby

Serve Static Files via HTTP

$ ruby -run -e httpd DOCUMENT_ROOT [OPTIONS]
Argument Description
DOCUMENT_ROOT Directory to serve
Option Short Description Example
–bind-address=ADDR -b IP address to bind to -b 127.0.0.1
–port=NUM -p Port number to listen on -p 8080
–max-clients=MAX -m Max number of simultaneous clients -m 2
–temp-dir=DIR -t Temporary directory to use -t /tmp
–do-not-reverse-lookup -d Disable reverse lookup -d
–request-timeout=SECOND -r Request timeout (in seconds) -r 2
–http-version=VERSION   HTTP version --http-version=1.0
  -v Start WEBrick in verbose mode -v

Further Reading

More Idiosyncratic Ruby