diff --git a/src/lib/common.sh b/src/lib/common.sh
new file mode 100644
index 0000000..89c4e87
--- /dev/null
+++ b/src/lib/common.sh
@@ -0,0 +1,50 @@
+#! /usr/bin/env bash
+
+# common.sh - common functions.
+# Copyright (c) 2022 ge <https://nixhacks.net/>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+log() {
+    # Logger. Write message to __log_file.
+    #
+    # Usage: log [-p] MESSAGE
+    #
+    # Can read from STDIN. Removes ANSI escape codes from log message.
+    # Echo message to STDOUT with '-p' option.
+
+    local message
+    local print
+    local log_file
+
+    log_file="$__log_file"
+
+    # If no arguments passed OR '0' descriptor is open, then read from descriptor.
+    # If no arguments AND '0' descriptor is closed, then 'message' will not be set.
+    [[ "$#" == 0 || -t 0 ]] || message="$(cat <&0)"
+
+    while (( "$#" )); do
+        case "$1" in
+            -p|--print) print=1; shift;;
+            -) message="$(cat <&0)"; shift "$#";;
+            *) message="$@"; shift "$#";;
+        esac
+    done
+
+    [[ "$print" == 1 ]] && echo "$message"
+
+    while read line; do
+        printf '[%s] [%s] %s\n' "$(date +'%d %b %Y %H:%M:%S %z')" "$0" "$line" >> "$log_file"
+    done <<< "$(sed -r 's/\x1B\[(([0-9]+)(;[0-9]+)*)?[m,K,H,f,J]//g' <<< "$message")"
+}