Python script to search for a symbol in libraries loaded by the dynamic linker (ld.so)

findsym.py

#!/usr/bin/env python

# Python script to search for a given symbol in libraries that are loaded by
# the dynamic linker (ld.so) in Linux.
#
# For example: to use the function `cabs` (absolute value of a complex number)
# you need to include the header <complex.h>, but the function itself is
# defined in libm.so.
#
# To find that out, you'd run:
#   sudo findsym cabs
#
# Obs: sudo is needed to run ldconfig without errors.
#
# Command-line equivalent:
#   $ ldconfig -v
#   $ nm -D <path-to-so-file> | grep -i <symbol>
#
# Based on:
#   http://stackoverflow.com/questions/9922949/how-to-print-the-ldlinker-search-path
#   http://stackoverflow.com/questions/1237575/how-do-i-find-out-what-all-symbols-are-exported-from-a-shared-object

import re
import sh
import sys

# Terminal ANSI colors.
class tcolors:
  RED   = '\033[31m'
  GREEN = '\033[32m'
  BLUE  = '\033[34m'
  ENDC  = '\033[0m'

current_user = sh.whoami().strip()

if current_user != "root":
  print(tcolors.RED + "You must be root to use this script. Please re-run with sudo." + tcolors.ENDC)
  exit(1)

if len(sys.argv) < 2:
  print(tcolors.RED + "Missing search term." + tcolors.ENDC)
  print(tcolors.RED + "Usage: %s <search-term>" % sys.argv[0] + tcolors.ENDC)
  exit(1)

ldconfig_out = sh.ldconfig("-v")

# Store current library directory we're inspecting
basepath = None

# Store absolute path to .so files.
files = []

search_term = sys.argv[1]
print(tcolors.BLUE + "Looking for term: " + search_term + tcolors.ENDC)

for line in ldconfig_out.splitlines():
  if line.startswith("\t"):
    if basepath is None:
      print("[error] Unexpected library name without a basepath.")
      exit(1)

    md = re.match('\t([^ ]+)', line)

    if md is not None:
      libname = md.group(1)
      files.append(basepath + "/" + libname)

  else:
    basepath = line[0:-1]

# Search all files found in ldconfig output for the given symbol.
for filename in files:
  nm_out = sh.nm("-D", filename)

  try:
    grep_out = sh.grep("-i", search_term, _in=nm_out)
    print(tcolors.GREEN + "\nFound match in file: " + filename + tcolors.ENDC)
    print(grep_out)
  except sh.ErrorReturnCode_1:
    # No match, but it's not an error.
    pass