2 files changed, 19 insertions, 0 deletions
diff --git a/deps.mk b/deps.mk
index 1db7bc5..7dd2086 100644
--- a/deps.mk
+++ b/deps.mk
@@ -4,6 +4,7 @@ sources.sh = \
 	src/mkdtemp \
 	src/mkstemp \
 	src/now \
+	src/pre \
 	src/tempname \
 	src/timestamp \
 	src/uuid \
diff --git a/src/pre b/src/pre
new file mode 100755
index 0000000..7ba0c47
--- /dev/null
+++ b/src/pre
@@ -0,0 +1,18 @@
+#!/bin/sh
+set -eu
+
+usage() {
+	cat <<-'EOF'
+		Usage:
+		  pre PREFIX < STDIN
+	EOF
+}
+
+
+PREFIX="${1:-}"
+eval "$(assert-arg -- "$PREFIX" 'PREFIX')"
+
+# FIXME: using "while" so we avoid GNU sed's buffering
+while read -r line; do
+	printf '%s: %s\n' "$PREFIX" "$line"
+done