+# Return a space-separated string of online CPU IDs, based on
+# /sys/devices/system/cpu/online, or from 0 to nproc - 1 otherwise.
+function get_online_cpus()
+{
+ local cpus=()
+ local range_re
+ if [ -f /sys/devices/system/cpu/online ]; then
+ range_re='([0-9]+)-([0-9]+)'
+ while read -r range ; do
+ if [[ "${range}" =~ ${range_re} ]] ; then
+ mapfile -t -O "${#cpus[*]}" cpus <<< $(seq "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}")
+ else
+ cpus+=("${range}")
+ fi
+ done < <(tr ',' $'\n' < /sys/devices/system/cpu/online)
+ else
+ read -r -a cpus <<< $(seq 0 $(( $(conf_proc_count) - 1 )) )
+ fi
+ echo "${cpus[*]}"
+}
+
+# Helpers for get_possible_cpus.
+function get_possible_cpus_count_from_sysfs_possible_mask()
+{
+ local max_possible_cpu_id
+
+ # The Awk script extracts the highest CPU id from the possible CPU
+ # mask. Assuming a numerical order, a field separator '-' and a record
+ # separator ','. The last value parsed is the highest id.
+ if [ -f /sys/devices/system/cpu/possible ]; then
+ max_possible_cpu_id=$(awk -F '-' 'BEGIN { RS = ","} { last = $NF } END { printf("%d\n", last) }' \
+ /sys/devices/system/cpu/possible)
+ echo "$((max_possible_cpu_id+1))"
+ else
+ echo "0"
+ fi
+}
+
+# This is a fallback if the possible CPU mask is not available. This will not
+# take into account unplugged CPUs.
+function get_max_cpus_count_from_sysfs_cpu_directories()
+{
+ local max_possible_cpu_id=0
+ local current_cpu_id
+
+ for i in /sys/devices/system/cpu/cpu[0-9]*; do
+ current_cpu_id="${i#/sys/devices/system/cpu/cpu}"
+ if [ "$current_cpu_id" -gt "$max_possible_cpu_id" ]; then
+ max_possible_cpu_id="$current_cpu_id"
+ fi
+ done
+
+ echo "$((max_possible_cpu_id+1))"
+}
+
+# Return the number of possible CPUs.
+function get_possible_cpus_count()
+{
+ local possible_cpus_count
+ possible_cpus_count=$(get_possible_cpus_count_from_sysfs_possible_mask)
+
+ if [ "$possible_cpus_count" -eq "0" ]; then
+ local configured_cpus_count
+ configured_cpus_count=$(getconf _NPROCESSORS_CONF)
+ possible_cpus_count=$(get_max_cpus_count_from_sysfs_cpu_directories)
+ possible_cpus_count=$((configured_cpus_count > possible_cpus_count \
+ ? configured_cpus_count \
+ : possible_cpus_count))
+ fi
+
+ echo "$possible_cpus_count"
+}
+
+# Return the list of exposed CPU.
+#
+# NOTE! Use it like so:
+#
+# IFS=" " read -r -a VARIABLE <<< "$(get_exposed_cpus_list)"
+function get_exposed_cpus_list()
+{
+ local list=()
+
+ for i in /sys/devices/system/cpu/cpu[0-9]*; do
+ list+=("${i#/sys/devices/system/cpu/cpu}")
+ done
+
+ echo "${list[@]}"
+}
+
+# Return any available CPU found. Do not make assumption about the returned
+# value, e.g. that it could be 0.
+function get_any_available_cpu()
+{
+ for cpu in $(get_online_cpus); do
+ echo "${cpu}"
+ break;
+ done
+}
+