diff --git a/rainfallwrangler/src/lib/record/records_recompress.mjs b/rainfallwrangler/src/lib/record/records_recompress.mjs
index 2a9f5e4..9ae2419 100644
--- a/rainfallwrangler/src/lib/record/records_recompress.mjs
+++ b/rainfallwrangler/src/lib/record/records_recompress.mjs
@@ -11,7 +11,9 @@ import gunzip from 'gunzip-maybe';
 import RecordsWriter from './RecordsWriter.mjs';
 
 async function records_recompress(dirpath_source, dirpath_target, items_per_file) {
-	const files = (await fs.promises.readdir(dirpath_source)).map(filename => path.join(dirpath_source, filename));
+	const files = (await fs.promises.readdir(dirpath_source))
+		.filter(filename => filename.endsWith(`.jsonl.gz`))
+		.map(filename => path.join(dirpath_source, filename));
 	
 	const reader = nexline({
 		input: files.map(filepath => new Readable().wrap(fs.createReadStream(filepath).pipe(gunzip())))
@@ -39,7 +41,7 @@ async function records_recompress(dirpath_source, dirpath_target, items_per_file
 		
 		if(new Date() - time_display > 500) {
 			const elapsed = new Date() - time_start;
-			process.stdout.write(`${pretty_ms(elapsed, { keepDecimalsOnWholeSeconds: true })} elapsed | ${i_file}/${i_this_file}/${i} files/thisfile/total |  ${(1000 / (elapsed / i)).toFixed(2)} lines/sec | ${items_per_file - i_this_file} left for this file    \r`);
+			process.stderr.write(`${pretty_ms(elapsed, { keepDecimalsOnWholeSeconds: true })} elapsed | ${i_file}/${i_this_file}/${i} files/thisfile/total |  ${(1000 / (elapsed / i)).toFixed(2)} lines/sec | ${items_per_file - i_this_file} left for this file    \r`);
 			time_display = new Date();
 		}
 	}
diff --git a/rainfallwrangler/src/subcommands/recompress/meta.mjs b/rainfallwrangler/src/subcommands/recompress/meta.mjs
new file mode 100644
index 0000000..4a6aca8
--- /dev/null
+++ b/rainfallwrangler/src/subcommands/recompress/meta.mjs
@@ -0,0 +1,8 @@
+"use strict";
+
+export default function(cli) {
+	cli.subcommand("recompress", "Recompress a source to a target directory with a given number of records per file.")
+		.argument("source", "Path to the source directory.", null, "string")
+		.argument("target", "Path to the target directory.", null, "string")
+		.argument("count-file", "The number of records to store in each record file. See the documentation for the optimal value of this number (default: 4096).", 64*64, "integer");
+}
diff --git a/rainfallwrangler/src/subcommands/recompress/recompress.mjs b/rainfallwrangler/src/subcommands/recompress/recompress.mjs
new file mode 100644
index 0000000..34333cb
--- /dev/null
+++ b/rainfallwrangler/src/subcommands/recompress/recompress.mjs
@@ -0,0 +1,21 @@
+"use strict";
+
+import fs from 'fs';
+
+import settings from "../../settings.mjs";
+
+import records_recompress from '../../lib/record/records_recompress.mjs';
+
+export default async function() {
+	if(typeof settings.source !== "string")
+		throw new Error(`Error: No source directory specified (see the --source CLI argument)`);
+	if(typeof settings.target !== "string")
+		throw new Error(`Error: No target directory specified (see the --target CLI argument)`);
+	
+	if(!fs.existsSync(settings.source))
+		throw new Error(`Error: The source directory at '${settings.source}' doesn't exist or you haven't got permission to access it.`);
+	if(!fs.existsSync(settings.target))
+		await fs.promises.mkdir(settings.target);
+	
+	await records_recompress(settings.source, settings.target);
+}
\ No newline at end of file
diff --git a/rainfallwrangler/src/subcommands/recordify/meta.mjs b/rainfallwrangler/src/subcommands/recordify/meta.mjs
index 8d428ed..ea39200 100644
--- a/rainfallwrangler/src/subcommands/recordify/meta.mjs
+++ b/rainfallwrangler/src/subcommands/recordify/meta.mjs
@@ -4,7 +4,7 @@ export default function(cli) {
 	cli.subcommand("recordify", "Converts rainfall radar and water depth data to a directory of .jsonl.gz files.")
 		.argument("water", "Path to the water depths file, formatted as a stream of terrain50 objects. May or may not be gzipped.", null, "string")
 		.argument("rainfall", "Path to the rainfall radar data, formatted as jsonl. May or may not be gzipped.",  null, "string")
-		.argument("count-file", "The number of records to store in each record file. See the documentation for the optimal value of this number (default: 4096).", 64*64)
+		.argument("count-file", "The number of records to store in each record file. See the documentation for the optimal value of this number (default: 4096).", 64*64, "integer")
 		.argument("rainfall-pattern", "The pattern of the number of time steps to average, as a comma-separated list of numbers. Given a point in time, each successive number specified works BACKWARDS from that point. For example, 1,4,10 would be 3 channels: 1 time step on it's own, then average the next 4 time steps, then average the next 10 steps (default: 1,3,3,5,12,24,48).", [1,3,3,5,12,24,48].reverse(), function(value) {
 			return value.split(",")
 				.map(el => parseInt(el))
diff --git a/rainfallwrangler/src/subcommands/uniq/meta.mjs b/rainfallwrangler/src/subcommands/uniq/meta.mjs
index 3468203..00a8c70 100644
--- a/rainfallwrangler/src/subcommands/uniq/meta.mjs
+++ b/rainfallwrangler/src/subcommands/uniq/meta.mjs
@@ -4,5 +4,5 @@ export default function(cli) {
 	cli.subcommand("uniq", "Deduplicates the entries in a directory of recordified files.")
 		.argument("source", "Path to the source directory.", null, "string")
 		.argument("target", "Path to the target directory.", null, "string")
-		.argument("count-file", "The number of records to store in each record file. See the documentation for the optimal value of this number (default: 4096).", 64*64);
+		.argument("count-file", "The number of records to store in each record file. See the documentation for the optimal value of this number (default: 4096).", 64*64, "integer");
 }
diff --git a/rainfallwrangler/src/subcommands/uniq/uniq.mjs b/rainfallwrangler/src/subcommands/uniq/uniq.mjs
index 27cbac7..2b842b7 100644
--- a/rainfallwrangler/src/subcommands/uniq/uniq.mjs
+++ b/rainfallwrangler/src/subcommands/uniq/uniq.mjs
@@ -15,5 +15,5 @@ export default async function() {
 	
 	const uniq_manager = new RecordUniqManager(settings.count_file);
 	await uniq_manager.deduplicate(settings.source, settings.target);
-	uniq_manager.close(); // Terminate the workerpool nowt hat we're done
+	uniq_manager.close(); // Terminate the workerpool now that we're done
 }
\ No newline at end of file