feat(user/bkdatediff):Add script to calculate timestamp differences

- Note: Uses GNU date

diff --git a/user/bkdatediff b/user/bkdatediff
new file mode 100644 (file)
index 0000000..8a669ab
--- /dev/null
+++ b/user/bkdatediff
@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Desc: Get time difference two between date-parsable strings in seconds
+# Usage: bkdatediff [STRING] [STRING]
+# Example: bkdatediff "2023-01-10T08:36:42+00" "2023-01-10T12:30:13+00"
+# Version 0.0.1
+
+yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
+die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
+must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
+check_depends() {
+    if ! command -v date 1>/dev/random 2>&1; then die "FATAL:Missing:date"; fi;
+    return 0;
+}; # check dependencies
+show_usage() {
+    cat <<'EOF'
+  USAGE:
+    bkdatediff [STRING1] [STRING2]
+
+  STRING1, STRING2
+    `date` parsable strings. (i.e. variable STR in `date --date='$STR'`)
+
+  EXAMPLE:
+    bkdatediff "2023-01-10T08:36:42+00" "2023-01-10T12:30:13+00"
+EOF
+};
+main() {
+    local t1 t2;
+    check_depends;
+    # check args
+    if [[ ! $# -eq 2 ]]; then show_usage; die "FATAL:Wrong number of args:$#"; fi;
+
+    # get unix epoch
+    t1="$(must date --date="$1" +%s)";
+    t2="$(must date --date="$2" +%s)";
+
+    # print diff in seconds
+    printf "%s\n" "$((t2 - t1))";
+}; # main program
+
+main "$@";