sleep.1: add copyright header

Makefile

@@ -28,7 +28,7 @@ RUSTLIBS = --extern getopt=build/o/libgetopt.rlib \
 CFLAGS += -I$(SYSEXITS)
 
 .PHONY: all
-all: dj false fop hru intcmp mm npc rpn scrut str strcmp swab true
+all: dj false fop hru intcmp mm npc rpn scrut sleep str strcmp swab true
 
 build:
 	# keep build/include until bindgen(1) has stdin support
@@ -118,6 +118,13 @@ scrut: build/bin/scrut
 build/bin/scrut: src/scrut.c build
 	$(CC) $(CFLAGS) -o $@ src/scrut.c
 
+.PHONY: sleep
+sleep: build/bin/sleep
+build/bin/sleep: src/sleep.rs build rustlibs
+	$(RUSTC) $(RUSTFLAGS) \
+		--extern sysexits=build/o/libsysexits.rlib \
+		-o $@ src/sleep.rs
+
 .PHONY: str
 str: build/bin/str
 build/bin/str: src/str.c build

docs/sleep.1

@@ -0,0 +1,53 @@
+.\" Copyright (c) 2024 DTB <trinity@trinity.moe>
+.\"
+.\" This work is licensed under CC BY-SA 4.0. To see a copy of this license,
+.\" visit <http://creativecommons.org/licenses/by-sa/4.0/>.
+
+.TH SLEEP 1
+
+.SH NAME
+
+sleep \(en wait a moment
+
+.SH SYNOPSIS
+
+sleep
+.RB [ seconds ]
+
+.SH DESCRIPTION
+
+Sleep waits the given amount of seconds before exiting.
+
+.SH DIAGNOSTICS
+
+Sleep exits successfully when the time specified has elapsed, or unsuccessfully
+if the time fails to elapse or if invoked incorrectly. In the latter scenario
+sleep will also print a usage synopsis.
+
+.SH BUGS
+
+User may still be tired after invoking sleep.
+
+.SH EXAMPLES
+
+The following invocation sleeps for five seconds.
+
+.RS
+.R sleep 5
+.RE
+
+The following sh(1p) command line sleeps for five minutes, or for sixty
+seconds, five times, using rpn(1) and xargs(1p).
+
+.RS
+.R $ rpn 60 5 '*' | xargs sleep
+.RE
+
+.SH COPYRIGHT
+
+Copyright (c) 2024 DTB. License AGPLv3+: GNU AGPL version 3 or later
+<https://gnu.org/licenses/gpl.html>.
+
+.SH SEE ALSO
+
+sleep(3)

src/sleep.rs

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2024 DTB <trinity@trinity.moe>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU Affero General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see https://www.gnu.org/licenses/.
+ */
+
+use std::{
+	env::args,
+	process::ExitCode,
+	thread::sleep,
+	time::Duration
+};
+
+extern crate sysexits;
+use sysexits::EX_USAGE;
+
+fn usage(s: &str) -> ExitCode {
+	eprintln!("Usage: {} [seconds]", s);
+	ExitCode::from(EX_USAGE as u8)
+}
+
+fn main() -> ExitCode {
+	let argv = args().collect::<Vec<String>>();
+
+	if argv.len() == 2 {
+		if let Ok(s) = argv[1].parse::<u64>() {
+			sleep(Duration::from_secs(s));
+			ExitCode::SUCCESS
+		} else {
+			usage(&argv[0])
+		}
+	} else {
+		usage(&argv[0])
+	}
+}