setting a timeout in an interactive bash shell script

steven.c.banks · 01-23-2009, 02:55 PM

I have a bash shell script that interacts with users, asking questions using echo and getting their replies using read. I need a way to exit the script if the user has not replied in some fixed period, e.g. five minutes.
If possible, I would like this to be global - i.e. set the timeout value once at the beginning of the script, instead of with each echo that asks for a response.
Any ideas? Thanks in advance...

colucix · 01-23-2009, 03:17 PM

The easy way is to use the -t option of read to specify a timeout in seconds for each input statement. The more complex way is one suggested by the Advanced Bash Scripting Guide, which defines a functions that can be used further through the script and its childs:

Code:

timedout_read() {
  timeout=$1
  varname=$2
  old_tty_settings=`stty -g`
  stty -icanon min 0 time ${timeout}0
  eval read $varname      # or just  read $varname
  stty "$old_tty_settings"
}

but as you can see its usage is quite the same as read -t. This function shows the correct global settings, anyway. Reference: http://www.tldp.org/LDP/abs/html/int...s.html#TIMEOUT

steven.c.banks · 01-23-2009, 04:07 PM

Thanks!! The read -t works perfectly. After the timeout, I can check the value of the read variable, and exit the script if it is null.