Bash – How to Wait for All Subprocesses of a Script

You can use sudo -nv 2> /dev/null to get an exit value of 0 when the credentials were there without being prompted for the password.

I have something like that for running fdisk and dropping the credentials if the were not there to begin with. Combined with catching Ctrl+C you would get something like (I am not a good bash programmer!):

#! /bin/bash
# this only removes credentials if logging in at the start was necessary

reset_sudo()
{
if [ $SUDOCREDCACHED != 0 ] ; then 
  # drop credentials if acquired in script
  sudo -k
fi
}

Ctrl_C()
{
  reset_sudo
  exit 0
}

sudo -nv 2> /dev/null
SUDOCREDCACHED=$?
if [ $SUDOCREDCACHED != 0 ] ; then 
  # acquire credentials
  sudo -v 
  if [ $? != 0 ] ; then 
    exit 1
  fi
fi

trap Ctrl_C SIGINT
### your stuff here ###
reset_sudo

I can't imagine any reason to write this code, and I'm not quite sure what the person who wrote this code was trying to achieve. wait here does nothing -- from its perspective, there are no child processes, so it will just exit immediately and basically act as a noop (wait itself executes in a child process due to command substitution, but that's unrelated).

As an aside, parsing the output of ls is quite fragile. Instead, consider just doing this:

for file in *.txt; do
    ...
done