Find which library (.a or .so) exports a symbol

find-lib.rb

#!/usr/bin/env ruby

begin
    require "parallel"
    PARALLEL = true
rescue LoadError
    PARALLEL = false
end

def each collection, &block
    if PARALLEL
        Parallel.each collection, &block
    else
        collection.each &block
    end
end

def usage
    puts "find-lib.rb path symbol"
    puts "Example: find-lib.rb /usr/lib printf"
    exit 1
end

dir = ARGV[0] or usage
what = ARGV[1] or usage

# TODO: Make this configurable
what = what.downcase

Dir.chdir dir do
    each Dir["**/*.{a,so}"] do |lib|
        found = `nm --extern-only --demangle '#{lib}' 2>/dev/null`
            .split("\n")
            .map { |i| i[/^[0-9a-f]+ (. .*)/i, 1] }
            .compact
            .select { |i| i.downcase.include? what }

        if ! found.empty?
            puts lib
            puts found.map { |i| "  - #{i}" }
        end
    end
end