Breaking a loop from the keyboard.

stf92 · 01-29-2012, 12:28 PM

Hi: I have a program like this:

Code:

#!/bin/bash

while [ 1 ]; do
   LIST=$(ls *wav)
   for i in $LIST; do 
       play $i
       sleep 10
   done
done

OK. When this script is running, I want to stop it whenever I want, for example with ^C. But ^C wont do. I think maybe substituting something like a read bultin command in the while argument would be a solution. Does read wait for the Return key?

Cedrik · 01-29-2012, 12:59 PM

Maybe use signal handler:

Code:

#!/bin/bash

kill_script ()
{
    echo "SIGTERM received, exiting..."
    exit
}

trap kill_script SIGINT SIGTERM

while [ 1 ]; do
   LIST=$(ls *wav)
   for i in $LIST; do 
       play $i
       sleep 10
   done
done

stf92 · 01-29-2012, 01:47 PM

Thank you very much. Your script is running.

David the H. · 01-31-2012, 08:34 AM

Some suggestions:

Don't parse ls for filenames. The shell's built-in globbing will do the job just fine here.
Use arrays to store lists of items, rather than scalar variables (Or just use globbing patterns directly).
QUOTE ALL OF YOUR VARIABLE SUBSTITUTIONS.
You should never leave the quotes off a variable expansion unless you explicitly want the resulting string to be word-broken by the shell.
http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes
Environment variables are generally all upper-case. So while not absolutely necessary, it's good practice to keep your own user variables in lower-case or mixed-case, to help differentiate them.

Code:

#!/bin/bash

kill_script ()
{
    echo "SIGTERM received, exiting..."
    exit
}

trap kill_script SIGINT SIGTERM


while true; do
	list=( *.wav )			# If it's not necessary to regenerate the list
					# every time it loops, leave this step outside.
	for i in "${list[@]}"; do 	# or just use "for i in *.wav" here.
		play "$i"
		sleep 10
	done
done

catkin · 01-31-2012, 09:05 AM

Does Ctrl+C work if you put the sleep 10 in the background and wait for it? Like this sample from lm_sensors' fancontrol script (the "Sleep while still handling signals" comment has always intrigued):

Code:

while true
do
    UpdateFanSpeeds
    # Sleep while still handling signals
    sleep $INTERVAL &
    wait $!
done

kalleanka · 01-31-2012, 09:51 AM

David the H. thanks for the links and explanation.

jasmine555 · 01-31-2012, 11:53 AM

I'am using linux fedora and mandrake. So I must forget kbhit(), even if some DOS emulators can run it but I don't want that. I did some seaching about termios and it seem to be very complex to use.

stf92 · 01-31-2012, 05:31 PM

Quote:

Originally Posted by David the H.

Some suggestions:

Don't parse ls for filenames. The shell's built-in globbing will do the job just fine here.
Use arrays to store lists of items, rather than scalar variables (Or just use globbing patterns directly).
QUOTE ALL OF YOUR VARIABLE SUBSTITUTIONS.
You should never leave the quotes off a variable expansion unless you explicitly want the resulting string to be word-broken by the shell.
http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes
Environment variables are generally all upper-case. So while not absolutely necessary, it's good practice to keep your own user variables in lower-case or mixed-case, to help differentiate them.

Code:

#!/bin/bash

kill_script ()
{
    echo "SIGTERM received, exiting..."
    exit
}

trap kill_script SIGINT SIGTERM


while true; do
	list=( *.wav )			# If it's not necessary to regenerate the list
					# every time it loops, leave this step outside.
	for i in "${list[@]}"; do 	# or just use "for i in *.wav" here.
		play "$i"
		sleep 10
	done
done

Thank you very much for your tips. About variable substitution I've had long correspondence in the forum. It seems to be a golden rule.