Re: Cooless with feh

[Todd Gruhn <tgruhn2%gmail.com@localhost>]

I tweeked it.

feh --bg-fill   -g +0+"$y"
/usr/local/share/wallpapers/MATRIX-screen-1920x1080.jpg || exit


I cant see *.jpg moving up. It looks like the 'feh --bg-fill' that I
use in .xinitrc (doing this on/in the root-window)


On Mon, Sep 14, 2026 at 3:37 PM Todd Gruhn <tgruhn2%gmail.com@localhost> wrote:
>
> What does "  sh -ec '  " mean?
> I am assuming "/bin/sh -ec ' "
>
> I rarely do shell -- usual perl
>
> On Mon, Sep 14, 2026 at 12:36 PM Robert Elz <kre%munnari.oz.au@localhost> wrote:
> >
> >     Date:        Sun, 13 Sep 2026 17:49:57 -0600
> >     From:        "DTB" <trinity@tebibyte.media>
> >     Message-ID:  <DLELAOTJGZH1.3D0Z8QIIQ9UNX@tebibyte.media>
> >
> >   | # I have not tried this! You may have to debug.
> >
> > Yes.
> >
> >   | sh -ec '
> >   | while :; do
> >   |     pkill feh || true
> >   |     feh --class wallpaper -g +0+$y /path/to/wallpaper.tif
> >   |
> >   |     y=$(echo $y 1 + p | dc) # +1 per round
> >   |     test $y -gt 100 && y=0  # 0-100
> >   |     sleep 5                 # 5s
> >   | done'
> >
> > I know nothing about feh, or moving wallpapers (can't even imagine
> > wanting that) or how smooth a technique like that would be, but as
> > a sh script that's just painful to look at.
> >
> > Instead try:
> >
> > sh -c ' y=0
> >         while :
> >         do
> >                 pkill feh 2>/dev/null
> >                 feh --class wallpaper -g +0+"$y" /path/to/wallpaper.tif || exit
> >                 y=$(( y + 1 > 100 ? 0 : y + 1 ))
> >                 sleep 5 || exit
> >         done'
> >
> > No evil -e, and because of that, no need for the || true after the pkill
> > (but redirecting stderr, if there is no feh running, no need to be told
> > about it), the next line might (probably does, but as I don't know feh
> > I'm not sure)
> >
> >                 feh --class wallpaper -g +0+"$y" /path/to/wallpaper.tif &
> >
> > instead of what I put there - depends whether feh just loads the wallpaper
> > and exits (in which case you want the first version with "|| true")
> > or if it remains running, in which case you need the version with '&'
> > instead, and in that case, between the pkill and the feh you also
> > need to add "wait" (just that as command), or perhaps "wait $! || :"
> > with the $! unquoted, so the first time it will just be "wait" which
> > should do nothing, and later times it will wait for the previous "feh"
> > to have exited before starting a new one - but starting async ('&' processes)
> > and never waiting for them to exit isn't a good idea (it won't make
> > zombie processes, the shell cleans up, but it is also remembering all
> > the exit status values for no reason).
> >
> > The "sleep 5 || exit" as I expect that most of the time, that "sleep"
> > will be what is running, and if interrupted or killed in some other way,
> > you want the whole script to exit, not just iterate one more time.  That's
> > the place where the -e might have automated that, but it really is better
> > to decide when the script should exit because of an error, and code that
> > explicitly, rather than hoping -e will work as desired (it often doesn't).
> >
> > And to answer the on-list question, 'y' would be the y coordinate of the
> > image on the screen, the original script didn't initialise it, hence you
> > probably would get an error from "-g +0+" as the opion to feh the first
> > time, and the y=$(echo $y 1 + p | dc) wouldn't have worked either.
> > This version will gradually move the top of the wallpaper down the
> > screen.   To move up, init y to 100, and change the "y=" line in the
> > loop to be:
> >         y=$(( y - 1 < 0 ? 100 : y - 1 ))
> >
> > It is quite likely that "100" is wrong, in both versions, and needs to
> > be the vertical size of your screen, but again, I don't know feh, nor
> > how it interprets its args, that might be a percentage of the screen size,
> > rather than a pixel count, for all I know.
> >
> > kre
> >
> > ps: the script as a whole (moving down) using async feh might be ...
> >
> > sh -c ' y=0
> >         while :
> >         do
> >                 pkill feh 2>/dev/null
> >                 wait $! || :
> >                 feh --class wallpaper -g +0+"$y" /path/to/wallpaper.tif &
> >                 y=$(( y + 1 > 100 ? 0 : y + 1 ))
> >                 sleep 5 || exit
> >         done'
> >
> >