Windows – Utility to search and replace text in files including subdirectories in Windows

Figured it out myself. Because Powershell works with .net objects rather than text, you need to use get-content to expose the contents of the text files. So to perform what I was trying to do in the question, use:

compare-object (get-content one.txt) (get-content two.txt)

I'd use Python for this. Put all this code into a file called mass_replace and "chmod +x mass_replace":

#!/usr/bin/python

import os
import re
import sys

def file_replace(fname, s_before, s_after):
    out_fname = fname + ".tmp"
    out = open(out_fname, "w")
    for line in open(fname):
        out.write(re.sub(s_before, s_after, line))
    out.close()
    os.rename(out_fname, fname)


def mass_replace(dir_name, s_before, s_after):
    for dirpath, dirnames, filenames in os.walk(dir_name):
        for fname in filenames:
            f = fname.lower()
            # example: limit replace to .txt, .c, and .h files
            if f.endswith(".txt") or f.endswith(".c") or f.endswith(".h"):
                f = os.path.join(dirpath, fname)
                file_replace(f, s_before, s_after)

if len(sys.argv) != 4:
    u = "Usage: mass_replace <dir_name> <string_before> <string_after>\n"
    sys.stderr.write(u)
    sys.exit(1)

mass_replace(sys.argv[1], sys.argv[2], sys.argv[3])

For a single search and replace of one string in one type of file, the solution with find and sed isn't bad. But if you want to do a lot of processing in one pass, you can edit this program to extend it, and it will be easy (and likely to be correct the first time).