如何从PHP写入命名的Linux管道？

Question

I have the following bash script:

server_control_pipe="/var/custom_pipe_file_name"
init_script="/usr/sbin/service [somedaemon]"

mkfifo -m 666 "$server_control_pipe"

while read line <"$server_control_pipe"
 do
  echo "Received $line"
  if [[ "$line" == 'stop' ]]; then
    $init_script stop
  elif [[ "$line" == 'start' ]]; then
    $init_script start
  elif [[ "$line" == 'stoppipe' ]]; then
    break
  fi
  echo "Waiting..."
done

echo "END"

...and the following PHP script:

<?php
define('SERVER_CONTROL_PIPE', "/var/custom_pipe_file_name");

if(false === file_put_contents(SERVER_CONTROL_PIPE, "start\n", FILE_APPEND))
    throw new Exception("Could not write to server control pipe");

When running the PHP script, the loop in the bash script seems to terminate and the bash script simply outputs END.

To try to find out why it does that, I replaced my PHP script with this code:

<?php
define('SERVER_CONTROL_PIPE', "/var/custom_pipe_file_name");

$f = fopen(SERVER_CONTROL_PIPE, 'w');
if(false === $f)
    throw new Exception("Could not open server control pipe");

$ret = fwrite($f, 'start\n');
if(false === $ret)
    throw new Exception("Could not write to server control pipe");

fclose($f);

I found out that the bash script loop terminates whenever fopen is called.

So my question boils down to: How do I have to open the pipe in PHP in order to not break the bash script loop?

Answer 1

If you want the script to run all the time then you should have while true instead of while read line, eg:

while :
do
    echo "Press [CTRL+C] to stop.."
    sleep 1
done

If you do read line you will read file contents of the file at that state and finish execution.