Script for yad (zenity,xdialog) Audio volume slider

[shep]

Another script that works but likely could be improved. I output to x11/yad but x11/xenity
or x11/xdialog could likely be used.
Quick background:
sndio volume range: 0.000 -> 1.000 sndioctl(1)

yad_sndioctl.sh

#!/bin/sh
# Modified from rufwoof on Puppy Linux forum
# retrieve sndioctl volume level
SNDIO_VALUE=`sndioctl | grep output.level | cut -d "=" -f 2`
SNDIO_VALUE=`printf "%.2f\n" $SNDIO_VALUE`
# adjust VALUE to 0 to 100 with rounded values
YAD_VALUE=`echo $SNDIO_VALUE*100 | bc`
YAD_VALUE=`printf "%.2f\n" "$YAD_VALUE"`
# Feed YAD_VALUE to yad scale and output to sndioctl
yad --scale --page=2 --window-icon=audio-volume-medium --title="Volume" \
--vertical --on-top --width=32 --height=200 --posx=-134 \
--posy=39 --value=$YAD_VALUE \
--no-buttons --close-on-unfocus --undecorated \
--print-partial | while read x ; \
do x=`echo "scale=2 ; $x/100" | bc`
sndioctl output.level=$x 1>/dev/null ; \
done

I tried using awk but the invocation started with a "0" (zero) value when the script ran and I wondered if the awk value was not an integer? Considered declaring SNDIO_VALUE/YAD_VALUE as integers (int) and using expr rather than echo'ing to bc. Anyone have a online reference for ksh posix compliance? Comments/tweaks appreciated.

[Head_on_a_Stick]

What was the awk command that you tried?

As in the last thread a search isn't needed if the sndioctl variable is specified so

sndio_value=$(sndioctl output.level | awk -F'=' '{print $2}')

But using awk in this way should be functionally equivalent to the cut command in your script so you could try that instead if you prefer.

I'm not really familiar with YAD so I can't comment on that.

[shep]

Thanks. When I stepped through it last night, awk would pull the value but I'm not sure the numeric manipulations were working fully. x11/yad would display a volume level and the slider would be set to "0" even though music was audible. Using the slider would adjust volume.

#!/bin/sh
sndio_value=$(sndioctl output.level | awk -F'=' '{print $2}')
sndio_value=`printf "%.2f\n" $sndio_value`
# adjust VALUE to 0 to 100 with rounded values
yad_value=$(echo $sndio_value*100 | bc)
yad_value=$(printf "%.2f\n" "$yad_value")
# Feed yad_value to yad scale and output to sndioctl
yad --scale --page=2 --window-icon=audio-volume-medium --title="Volume" \
--vertical --on-top --width=32 --height=200 --posx=-174 \
--posy=49 --value=$yad_value \
--no-buttons --close-on-unfocus --undecorated \
--print-partial | while read x ; \
do x=$(echo "scale=2 ; $x/100" | bc)
sndioctl output.level=$x 1>/dev/null ; \
done

The above works. Would using expr(1) in lieu of "| bc" be cleaner?

[Head_on_a_Stick]

Originally Posted by shep

TWould using expr(1) in lieu of "| bc" be cleaner?

What do you mean by "cleaner"? I don't think there's anything wrong with either tool in this situation. Did you know awk can do floating point maths? As can shells/ksh93. I suppose expr(1) is part of POSIX, if that matters to you.

And I forgot to answer this:

Originally Posted by shep

Anyone have a online reference for ksh posix compliance?

OpenBSD's KornShell implementation can be run with the POSIXLY_CORRECT variable set. See the POSIX mode section of ksh(1) for more on this.

For an overview of the POSIX shell specification see https://pubs.opengroup.org/onlinepub...V3_chap02.html

More generally, I like to use https://shellcheck.net to pick up problems in shell scripts. It will detect any deviations from POSIX compliance in /bin/sh scripts.

[shep]

Thanks. My shell scripting has largely been searching for a specific function and then adapting it. I'm also about 200 pages into a book on shell scripting which is pretty generic and is more bash than ksh.