LineCache - A module to read and cache file information of a Ruby program.


The LineCache module allows one to get any line from any file, caching the lines and file information on first access to the file. Although the file may be any file, the common use is when the file is a Ruby script since parsing of the file is done to figure out where the statement boundaries are.

The routines here may be is useful when a small random sets of lines are read from a single file, in particular in a debugger to show source lines.


require 'linecache'
lines = LineCache::getlines('/tmp/myruby.rb')
# The following lines have same effect as the above.
$: << '/tmp'
Dir.chdir('/tmp') {lines = LineCache::getlines('myruby.rb')

line = LineCache::getline('/tmp/myruby.rb', 6)
# Note lines[6] == line (if /tmp/myruby.rb has 6 lines)

LineCache::update_cache   # Check for modifications of all cached files.


This is a port of the module of the same name from the Python distribution.

The idea for how TraceLineNumbers works, and some code was taken
from ParseTree by Ryan Davis.

Other stuff


Rocky Bernstein <>


Copyright © 2007, 2008 Rocky Bernstein Released under the GNU GPL 2 license


This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

$Id: README 169 2009-02-08 17:19:33Z rockyb $