Implementing infinite wait in shell scripting

Question

This may sound trivial, but I\'m pretty sure this question hasn\'t been asked, or at least I can\'t find it.

I\'m looking for a way to construct an infinite wait

Answer 1

Why do not you use sleep forever? This is designed to forever block.

Answer 2

you can use a named pipe for your read:

mkfifo /tmp/mypipe
#or mknode /tmp/mypipe p

if you later want to send different arbitrary "signals" to the pipe, the read can be use in combination with a case statement to take appropriate actions (even useful ones)

while read SIGNAL; do
    case "$SIGNAL" in
        *EXIT*)break;;
        *)echo "signal  $SIGNAL  is unsupported" >/dev/stderr;;
    esac
done < /tmp/mypipe

Answer 3

#!/bin/sh
at_term() {
  echo 'Terminated.'
  exit 0
}
trap at_term TERM
echo $$
while true; do
  sleep 20 &
  wait $!
done

Answer 4

What's wrong with your 2nd option but forcing it to read from stdin ? (Requires bash)

while true; do
  read
done < /dev/stdin

From man bash

Bash handles several filenames specially when they are used in redirections, as described in the following table:

          /dev/stdin
                 File descriptor 0 is duplicated.

Answer 5

SIGTERM sent to a process is delivered by the kernel to the process whether it is sleeping or not.

Try experimenting, maybe like this (bash example)

sleep 20 &
kill $! && fg

Answer 6

Here's a solution without a loop:

#!/usr/local/bin/dash

echo $$

# -$$: kill process group (parent and children)
#trap 'trap - TERM; kill 0' TERM
#trap 'trap - INT TERM; kill 0' INT TERM

trap 'trap - TERM; kill -s TERM -- -$$' TERM

tail -f /dev/null & wait

exit 0