1 files changed, 51 insertions, 0 deletions

diff --git a/suspend-below-battery-capacity b/suspend-below-battery-capacity
new file mode 100755
index 0000000..114cf9b
--- /dev/null
+++ b/suspend-below-battery-capacity
@@ -0,0 +1,51 @@
+#!/bin/bash
+default_capacity_threshold=50
+
+if [ -e /usr/lib/bash/sleep ]
+then
+    enable -f /usr/lib/bash/sleep sleep
+else
+    echo 'Warning: not found: /usr/lib/bash/sleep (try: "sudo apt install bash-builtins")' >&2
+fi
+
+main()
+{
+    capacity_threshold=${1:-$default_capacity_threshold}
+    while true
+    do
+        check_batteries /sys/class/power_supply/BAT*
+        sleep 1
+    done
+}
+
+check_batteries()
+{
+    for dir in "$@"
+    do
+        [ -d "$dir" ] || continue
+        check_battery "$dir"
+    done
+}
+
+check_battery()
+{
+    battery_dir=$1
+
+    read status < "$battery_dir"/status || return
+    [ "$status" = Discharging ] || return 0
+
+    read capacity < "$battery_dir"/capacity || return
+    case "$capacity" in
+        '' | *[^0-9]*)
+            echo "Error: unexpected value for battery capacity: $capacity" >&2
+            return 1
+            ;;
+    esac
+
+    if [ "$capacity" -lt "$capacity_threshold" ]
+    then
+        systemctl suspend
+    fi
+}
+
+main "$@"