Programatically determine if an script is being executed on laptop or desktop?

Question

Is there any reliable way to determine (programmatically) from within a bash script if it is being executed on a laptop or a desktop computer?

I could obviously just prompt the user to ask them, but that is pretty clunky.

Answer 1

Looking at whether or not the system has a battery is not reliable - a UPS connected to the system (not just for power, but over USB as well for automatic shutdown and battery monitoring) may show up as a battery.

There is a nice reliable way however:

dmidecode --string chassis-type

On a laptop, this will return one of "Laptop", "Notebook" "Portable", or "Sub Notebook" (depending on what the manufacturer coded into the BIOS). There is a full list of possible values at "Identifying the Chassis Type of a Computer" in the Windows 2000 Scripting Guide - don't worry about it being a Microsoft TechNet page, this is not OS specific.

dmidecode can also get information about the hardware manufacturer, system serial number (sometimes), etc.

Answer 2

To avoid using sudo, you can read the contents of /sys/class/dmi/id/chassis_type. It appears conform to the following table:

• 1 Other
• 2 Unknown
• 3 Desktop
• 4 Low Profile Desktop
• 5 Pizza Box
• 6 Mini Tower
• 7 Tower
• 8 Portable
• 9 Laptop
• 10 Notebook
• 11 Hand Held
• 12 Docking Station
• 13 All in One
• 14 Sub Notebook
• 15 Space-Saving
• 16 Lunch Box
• 17 Main System Chassis
• 18 Expansion Chassis
• 19 SubChassis
• 20 Bus Expansion Chassis
• 21 Peripheral Chassis
• 22 Storage Chassis
• 23 Rack Mount Chassis
• 24 Sealed-Case PC

Answer 3

Debian Solution:

To find whether a machine running Debian is a laptop, try:

[ -d /sys/module/battery ] && echo "Yes it's a laptop"

This approach does not require root privileges.

On other distributions, however, this directory seems to exist, at least in skeleton form, regardless of whether or not there is a battery. From the comments (below), these distributions include CentOS, Ubuntu, and the Ubuntu-derived distribution of Linux Mint.

More General Solution

Although it does not work on my Debian systems, the solution proposed by Alex reportedly works on Ubuntu & CentOS. Thus suggests, for greater generality, a possible combined solution:

[ -f /sys/module/battery/initstate ] || [ -d /proc/acpi/battery/BAT0 ] && echo "Yes it's a laptop"

This approach does not require root privileges.

More Details

On a Debian system with an actual battery, the /sys/module/battery directory contains many files. One such file is /sys/module/battery/initstate which contains the text live. On Ubuntu, however, these files do not exist even on actual laptops. Thus, it appears that the presence of the file /sys/module/battery/initstate can be used to test for a laptop running Debian.

On Debian systems that I tested, by contrast, the /proc/acpi/battery directory did not exist.

Answer 4

I'd check if the computer has a battery installed. And the following is one way to test:

if [ -d /proc/acpi/battery/BAT* ]; then
  echo has a battery
fi

Answer 5

If checking for battery existence is good enough, you can use this shell function:

# Checks whether system is a laptop.
#
# @returns {bool}   true if system is a laptop.
function is_laptop() {
    local d
    for d in /sys/class/power_supply /proc/acpi/battery; do
        [[ -d "$d" ]] && find $d -mindepth 1 -maxdepth 1 -name 'BAT*' -print0 -quit 2>/dev/null | grep -q . && return 0
    done

    # note we're checking /sys/class/power_supply/battery/status for WSL
    for d in /sys/class/power_supply/battery/status /sys/module/battery/initstate; do
        [[ -f "$d" ]] && return 0
    done

    return 1
}

Have been using this on Debian for years. Note this works also for Debian running in WSL or virtualbox.

Edit: generalized from other answers in this thread to catch more cases.