1 files changed, 86 insertions, 0 deletions
diff --git a/bin/ifnew b/bin/ifnew
new file mode 100755
index 0000000..8d5c434
--- /dev/null
+++ b/bin/ifnew
@@ -0,0 +1,86 @@
+#!/bin/sh
+set -eu
+
+usage() {
+	cat <<-'EOF'
+		Usage:
+		  ifnew FILE
+		  ifnew -h
+	EOF
+}
+
+help() {
+	cat <<-'EOF'
+
+
+		Options:
+		  -h, --help    show this message
+
+		  FILE          the target to compared against
+
+
+		Compare STDIN to FILE, and only write to FILE if STDIN content
+		differs from FILE content.
+
+
+		Examples:
+
+		  Create a new file, don't update it afterwards, and update it
+		  as the content changes:
+
+		    $ echo aaa | ifnew  new-file
+		    $ stat --print='%y' new-file
+		    # timestamp 1
+
+		    $ echo aaa | ifnew  new-file
+		    $ stat --print='%y' new-file
+		    # timestamp 1
+
+		    $ echo bbb | ifnew  new-file
+		    $ stat --print='%y' new-file
+		    # timestamp 2
+	EOF
+}
+
+
+for flag in "$@"; do
+	case "$flag" in
+		--)
+			break
+			;;
+		--help)
+			usage
+			help
+			exit
+			;;
+		*)
+			;;
+	esac
+done
+
+while getopts 'h' flag; do
+	case "$flag" in
+		h)
+			usage
+			help
+			exit
+			;;
+		*)
+			usage >&2
+			exit 2
+			;;
+	esac
+done
+shift $((OPTIND - 1))
+
+FILE="${1:-}"
+eval "$(assert-arg -- "$FILE" 'FILE')"
+
+
+STDIN="$(mkstemp)"
+trap 'rm -f "$STDIN"' EXIT
+
+cat - > "$STDIN"
+if ! cmp -s "$STDIN" "$FILE"; then
+	mv "$STDIN" "$FILE"
+fi