diff --git a/txt2printr.sh b/txt2printr.sh
index d16956c..99f6a45 100755
--- a/txt2printr.sh
+++ b/txt2printr.sh
@@ -1 +1,26 @@
 #/bin/bash
+#
+# Sends an ascii-art text file to a parallel port needle/dot-matrix printer.
+#
+# Usage: ./txt2printr.sh [ascii-art.txt]
+# Env:   PRINTER_DEV - printer device node (default: /dev/lp0)
+
+infile="${1:-ascii-img.txt}"
+dev="${PRINTER_DEV:-/dev/lp0}"
+
+if [ ! -f "$infile" ]; then
+    echo "txt2printr: file not found: $infile" >&2
+    exit 1
+fi
+
+if [ ! -w "$dev" ]; then
+    echo "txt2printr: cannot write to printer device: $dev" >&2
+    echo "txt2printr: set PRINTER_DEV to override, or check permissions/parport module" >&2
+    exit 1
+fi
+
+{
+    printf '\x1b\x40'        # ESC @ - reset printer (ESC/P and IBM Proprinter compatible)
+    sed 's/$/\r/' "$infile"  # CRLF line endings, needed for raw writes to avoid staircasing
+    printf '\x0c'            # form feed - eject the page
+} > "$dev"