diff options
Diffstat (limited to 'lib/irb/pager.rb')
-rw-r--r-- | lib/irb/pager.rb | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/lib/irb/pager.rb b/lib/irb/pager.rb new file mode 100644 index 0000000000..16066cf273 --- /dev/null +++ b/lib/irb/pager.rb @@ -0,0 +1,61 @@ +# frozen_string_literal: true + +module IRB + # The implementation of this class is borrowed from RDoc's lib/rdoc/ri/driver.rb. + # Please do NOT use this class directly outside of IRB. + class Pager + PAGE_COMMANDS = [ENV['RI_PAGER'], ENV['PAGER'], 'less', 'more'].compact.uniq + + class << self + def page + if STDIN.tty? && pager = setup_pager + begin + pid = pager.pid + yield pager + ensure + pager.close + end + else + yield $stdout + end + # When user presses Ctrl-C, IRB would raise `IRB::Abort` + # But since Pager is implemented by running paging commands like `less` in another process with `IO.popen`, + # the `IRB::Abort` exception only interrupts IRB's execution but doesn't affect the pager + # So to properly terminate the pager with Ctrl-C, we need to catch `IRB::Abort` and kill the pager process + rescue IRB::Abort + Process.kill("TERM", pid) if pid + nil + rescue Errno::EPIPE + end + + private + + def setup_pager + require 'shellwords' + + PAGE_COMMANDS.each do |pager| + pager = Shellwords.split(pager) + next if pager.empty? + + if pager.first == 'less' || pager.first == 'more' + pager << '-R' unless pager.include?('-R') + end + + begin + io = IO.popen(pager, 'w') + rescue + next + end + + if $? && $?.pid == io.pid && $?.exited? # pager didn't work + next + end + + return io + end + + nil + end + end + end +end |