A Weird Imagination

Useful global keyboard shortcuts

Most desktop environments provide options for customizing keyboard shortcuts. In XFCE, there's settings panels for both for window manager shortcuts and application shortcuts. While the term "application shortcuts" suggests using them for launching applications, and many keyboards do have special keys for launching a music player or a calculator that I do have set up, I don't find myself using those much. I have buttons on my panel for applications that I launch often; if I'm going to be clicking away into a new application, I don't find clicking on the panel to be an additional inconvenience.

On the other hand, "application shortcuts" can be used for launching arbitrary scripts, including ones don't involve switching contexts.

Keys to use

Many keyboards have extra keys intended for global commands labeled with various symbols. If you have them, you can be creative about what you want them to mean and even combine them with modifiers (Shift, Ctrl, etc.) to get more inputs. On the other hand, if you have a more traditional keyboard layout (which is likely the case on a laptop), your choices are more limited. To avoid confusion, it's generally best to use the Windows key (usually called the Super key in Linux) for global shortcuts as it is not usually used for anything else.

Shortcut ideas

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Limit processor usage of multiple processes

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The problem

In last week's post, I discussed using cpulimit on multiple processes in the special case of web browsers, but I wanted a more general solution.

The solution

cpulimit-all.sh is a wrapper around cpulimit which will call cpulimit many times to cover multiple processes of the same name and subprocesses.

Using that script, the follow is the equivalent of the script from last week to limit all browser processes to 10% CPU:

cpulimit-all.sh --limit=10 --max-depth=1 \
    -e firefox -e firefox-esr -e chromium -e chrome

But also, we can add a couple options to include any grandchild processes and check for new processes to limit every minute:

cpulimit-all.sh --limit=10 --max-depth=2 \
    -e firefox -e firefox-esr -e chromium -e chrome \
    --watch-interval=1m

The details

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Limit web browser processor usage

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The problem

cpulimit is a useful utility for stopping a program from wasting CPU, but it only limits a single process. As all modern web browsers use process isolation, limiting just a single process doesn't do very much, we actually want to limit all of the browser processes.

The solution

The following script will limit the CPU usage of all browser processes to $LIMIT percent CPU. Note that the limit is per process not total over all processes, so you may want to set it quite low to actually have an effect.

LIMIT=10 # Hard-code a limit of 10% CPU as an example.

# Kill child processes (stop limiting CPU) on script exit.
for sig in INT QUIT HUP TERM; do
  trap "
    pkill -P $$
    trap - $sig EXIT
    kill -s $sig "'"$$"' "$sig"
done
trap cleanup EXIT

# Find and limit all child processes of all browsers.
for name in firefox firefox-esr chromium chrome
do
    for ppid in $(pgrep "$name")
    do
        cpulimit --pid="$ppid" --limit="$LIMIT" &
        for pid in "$ppid" $(pgrep --parent "$ppid")
        do
            cpulimit --pid="$pid" --limit="$LIMIT" &
        done
    done
done

The details

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