src/ifnew: Add working utility

2 files changed, 34 insertions, 0 deletions

diff --git a/deps.mk b/deps.mk
index dec3a78..0a6adda 100644
--- a/deps.mk
+++ b/deps.mk
@@ -2,6 +2,7 @@ sources.sh = \
 	src/assert-arg \
 	src/clock \
 	src/color \
+	src/ifnew \
 	src/minutes \
 	src/mkdtemp \
 	src/mkstemp \
diff --git a/src/ifnew b/src/ifnew
new file mode 100755
index 0000000..c293f63
--- /dev/null
+++ b/src/ifnew
@@ -0,0 +1,33 @@
+#!/bin/sh
+set -eu
+
+usage() {
+	cat <<-'EOF'
+		Usage:
+		  ifnew [-v] FILE
+	EOF
+}
+
+MV_ARGS=''
+while getopts 'v' flag; do
+	case "$flag" in
+		(v)
+			MV_ARGS='-v'
+			;;
+		(*)
+			usage >&2
+			exit 2
+			;;
+	esac
+done
+shift $((OPTIND - 1))
+
+FILE="${1:-}"
+eval "$(assert-arg -- "$FILE" 'FILE')"
+
+
+STDIN="$FILE.$(uuid).tmp"
+trap 'rm -f "$STDIN"' EXIT
+
+cat - > "$STDIN"
+cmp -s "$STDIN" "$FILE" || mv $MV_ARGS "$STDIN" "$FILE"