sleep(1): initial implementation

Makefile

@@ -103,6 +103,13 @@ 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
+	$(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

src/dj.c

@@ -203,28 +203,28 @@ Io_fdseek(struct Io *io){
 	
 	if(!fdisstd(io->fd) && lseek(io->fd, io->seek, SEEK_SET) != -1)
 		return -1;
-	else if(io->fl == write_flags){
-		memset(io->buf, '\0', io->bs);
-		/* This is a dirty trick; rather than testing conditions and operating
-		 * likewise, because the parameters to read or write are going to be
-		 * the same either way, just use a function pointer to keep track of
-		 * the intended operation. */
-		op = (int (*)(int, void *, size_t))&write;
-		/* Function pointer casts are risky; this works because the difference
-		 * is in the second parameter and only that write(2) makes the buffer
-		 * const whereas read(2) does not. To avoid even the slightest
-		 * undefined behavior comment out the cast, just be ready for a
-		 * -Wincompatible-function-pointer-types if your compiler notices it.
-		 */
-	}else
-		op = &read;
 
-	/* We're going to cheat and use bufuse as the retval for write(2), which is
-	 * fine because it'll be zeroed as this function returns anyway. */
-	do{	if(	(io->bufuse = (*op)(io->fd, io->buf, MIN(io->bs, io->seek))) == 0)
-			/* second chance */
-			io->bufuse = (*op)(io->fd, io->buf, MIN(io->bs, io->seek));
-	}while((io->seek -= io->bufuse) > 0 && io->bufuse != 0);
+	/* repeated code to get the condition out of the loop */
+	if(io->fl == write_flags){
+		memset(io->buf, '\0', io->bs);
+		/* We're going to cheat and use bufuse as the retval for write(2),
+		 * which is fine because it'll be zeroed as this function returns
+		 * anyway. */
+		do{
+			if((io->bufuse = write(io->fd, io->buf, MIN(io->bs, io->seek)))
+					== 0)
+				/* second chance */
+				io->bufuse = write(io->fd, io->buf, MIN(io->bs, io->seek));
+		}while((io->seek -= io->bufuse) > 0 && io->bufuse != 0);
+	}else if(io->fl == read_flags){
+		do{
+			if((io->bufuse = read(io->fd, io->buf, MIN(io->bs, io->seek)))
+					== 0)
+				/* second chance */
+				io->bufuse = read(io->fd, io->buf, MIN(io->bs, io->seek));
+		}while((io->seek -= io->bufuse) > 0 && io->bufuse != 0);
+	}else
+		return EX_SOFTWARE;
 
 	io->bufuse = 0;
 

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_OK, 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::from(EX_OK as u8)
+		} else {
+			usage(&argv[0])
+		}
+	} else {
+		usage(&argv[0])
+	}
+}