How to get the width of terminal window in Ruby

Question

Have you ever noticed that if you run rake -T in rails the list of rake descriptions are truncated by the width of the terminal window. So there should be a way to get it in Ruby and Use it.

I'm printing some Ascii-art on the screen and I don't want it to be broken. therefore I need to find out the width of terminal at run time some how.

Any Idea how to do that?

Solution 1

I've found that on Ubuntu, none of the other methods specified here (ENV['COLUMNS'], tput columns or hirb) give the correct result if the terminal is resized while the Ruby application is running. This is not an issue for scripts, but it is an issue for interactive consoles, such as irb.

The ruby-terminfo gem is the best solution I've find so far to give the correct dimensions after a resize, but it requires that you install an additional gem, and is unix-specific.

The gem's usage is simple:

require 'terminfo'
p TermInfo.screen_size        # [lines, columns]

TermInfo internally uses TIOCGWINSZ ioctl for the screen size.

Alternatively, as mentioned by user83510, highline's system_extensions also works:

require 'highline'
HighLine::SystemExtensions.terminal_size # [columns, lines]

Interally, highline uses stty size on Unix, and other implementations for ncurses and Windows.

To listen for changes to the terminal size (instead of polling), we can trap the SIGWINCH signal:

require 'terminfo'
Signal.trap('SIGWINCH', proc { puts TermInfo.screen_size.inspect })

This is specifically useful for applications using Readline, such as irb:

Signal.trap('SIGWINCH', proc { Readline.set_screen_size(TermInfo.screen_size[0], TermInfo.screen_size[1]) })

Solution 2

There is a common unix command:

tput cols

This returns the width of the terminal.

Solution 3

def winsize
 #Ruby 1.9.3 added 'io/console' to the standard library.
 require 'io/console'
 IO.console.winsize
 rescue LoadError
 # This works with older Ruby, but only with systems
 # that have a tput(1) command, such as Unix clones.
[Integer(`tput li`), Integer(`tput co`)]
end

rows, cols = winsize
printf "%d rows by %d columns\n", rows, cols

Link

Solution 4

If you want your code to work across platforms, here's what I use: http://github.com/cldwalker/hirb/blob/master/lib/hirb/util.rb#L61-71

Also check out the system_extensions file in highline

Solution 5

Ruby actually comes with a built-in class called "Curses", which lets you do all kinds of things with the terminal window.

For example, you can do this:

require 'curses'

Curses.init_screen()

puts Curses.lines # Gives you the height of terminal window
puts Curses.cols # Gives you the width of terminal window

For more info: http://ruby-doc.org/stdlib-1.9.3/libdoc/curses/rdoc/Curses/Window.html

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