Waiting for a signal - mine not working

Thanks a lot John, it is working now. I dont think I will forget this one too soon.

mariusl wrote:

Hi
I am using this piece of code to read a signal and then wait for it to change:

M100

#!/bin/sh
halcmd sets ladder_in 1
~/linuxcnc/nc_files/waitfor ladder_out 1
halcmd sets ladder_in	0

waitfor

#!/bin/bash

if [ $# != 2 ]; then
    echo usage: $0 SignalName DesiredValue
    exit 1
fi

signal=$1
value=$2

while :; do
    set -- $(halcmd -s show sig $signal)
    if [ x"$2" == x"$value" ]; then
        exit 0
    fi
    sleep 1
done

It looks like the code never enters the loop but I have no way of telling. It will exit and turn the signal of right away.

Maybe it is me but I don't see how this could ever work! My BASH is rusty but it looks like you are comparing $2 to itself thus always exiting.

The HAL command actually returns a string of which the second value is compared to the second passed parameter. I hope it makes sense. anyway, the code works as per the above posts