to overwrite the line in many files with awk

linerewritten.awk

#!/usr/bin/awk -f
# GNU Awk 4.1.4, API: 1.1
# GNU bash, версия 4.4.12(1)-release (i586-suse-linux-gnu)
#
# copy linerewriter.awk to $HOME/bin/
# added   chmod +x $HOME/bin/linerewriter
# run linerewriter
#
# linerewriter target_dir_with_files Foo Bar
# Foo will be rewritten as Bar

function blue(s) { return "\033[1;37;1m" s "\033[0m" }

function listdir(   path) {
  cmd = "realpath " path "/*"
  while (cmd | getline filepath) {
    ARGV[ARGC++] = filepath
  }
  close(cmd)
}

BEGIN {
  length_argv = length(ARGV)
  "pwd" | getline basepath
#  files it's filepath array

  if (length_argv != 4) { exit 0 }

  path = ARGV[1]
  to = ARGV[2]
  replace = ARGV[3]

  for (i=0; i<length(ARGV); i++) {
    delete ARGV[i]
  }
  ARGC=0
  listdir(path)
}
{
  gsub(to, replace, $0)
  files[FILENAME] = files[FILENAME] $0 "\n"
}
END {
  for (file_path in files) {
    print files[file_path] > file_path
    sub(basepath "/", "", file_path)
    print "replaced in: " blue(" " file_path " ")
  }
}

https://asciinema.org/a/rjbw2J2Rg9o9PD7vU2kS20OtW
this version of the script is not stable