From 5926594690f03cf282b856cc53facbea8a42d88c Mon Sep 17 00:00:00 2001
From: Aaron LI <aly@aaronly.me>
Date: Thu, 25 Apr 2019 08:49:30 +0800
Subject: Add unix/gen-pass.sh: generate random passwords

---
 unix/gen-pass.sh | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100755 unix/gen-pass.sh

diff --git a/unix/gen-pass.sh b/unix/gen-pass.sh
new file mode 100755
index 0000000..4718b0c
--- /dev/null
+++ b/unix/gen-pass.sh
@@ -0,0 +1,81 @@
+#!/bin/sh
+#
+# Copyright (c) 2019 Aaron LI
+# MIT License
+#
+# Generate random passwords.
+#
+# Credit:
+# * How to generate a random string?
+#   https://unix.stackexchange.com/a/230676
+# * password-store:
+#   http://www.passwordstore.org/
+#
+
+# usage: generate ${characters} ${length}
+generate() {
+    local characters="$1"
+    local length="$2"
+    env LC_ALL=C tr -dc "${characters}" </dev/urandom |
+        head -c ${length}
+}
+
+usage() {
+    cat << _EOF_
+Generate random passwords.
+
+usage:
+    ${0##*/} [-n] [-l length] [count]
+
+options:
+    -n : no symbols, i.e., only alphabets and numbers
+    -l length : password length (default: 16)
+    count : number of passwords to generate (default: 1)
+_EOF_
+
+    exit 1
+}
+
+main() {
+    local characters="[:graph:]"
+    local length=16
+    local count=1
+
+    while getopts :hl:n opt; do
+        case ${opt} in
+        h)
+            usage
+            ;;
+        l)
+            length="${OPTARG}"
+            ;;
+        n)
+            characters="[:alnum:]"
+            ;;
+        \?)
+            echo "Invalid option -${OPTARG}"
+            usage
+            ;;
+        :)
+            echo "Option -${OPTARG} requires an argument"
+            usage
+            ;;
+        esac
+    done
+
+    shift $((${OPTIND} - 1))
+    if [ $# -eq 0 ]; then
+        :
+    elif [ $# -eq 1 ]; then
+        count="$1"
+    else
+        usage
+    fi
+
+    for i in $(seq ${count}); do
+        generate "${characters}" ${length}
+        echo
+    done
+}
+
+main "$@"
-- 
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