Very simple script to display a specified line in a file, plus the line immediately preceding and following it. I whipped this up as a quick solution to manually following a particularly vague stack trace from Jax (github.com/sinisterchipmunk/jax).

line

#!/usr/bin/env ruby

def fail(msg)
  puts msg
  puts
  exit
end

fail "Usage: line [filename] [lineno]" if !ARGV[0] || !ARGV[1] || !File.file?(ARGV[0])

lines = File.read(ARGV[0]).lines.to_a
lineno = ARGV[1].to_i - 1

fail "There are only #{lines.length} lines in the file" if lineno >= lines.length

print "  "
puts(lineno <= 0 ? "<bof>" : lines[lineno-1])

print "> "
puts lines[lineno]

print "  "
puts(lineno >= lines.length-1 ? "<eof>" : lines[lineno+1])