swab(1): don't accept positional arguments

docs/swab.1

@@ -11,7 +11,6 @@ swab \(en swap bytes
 .SH SYNOPSIS
 
 swab
-.RB [ -f ]
 .RB [ -w\ word_size ]
 .\"
 .SH DESCRIPTION
@@ -20,8 +19,6 @@ Swap the latter and former halves of a block of bytes.
 .\"
 .SH OPTIONS
 
-.IP \fB-f\fP
-Ignore SIGINT signal.
 .IP \fB-w\fP\ \fIword_size\fP
 Configures the word size; that is, the size in bytes of the block size on which
 to operate. The default word size is 2. The word size must be cleanly divisible

src/swab.rs

@@ -18,7 +18,7 @@
 
 use std::{
 	env::args,
-	io::{ stdin, stdout, Error, ErrorKind, Read, Write },
+	io::{ stdin, stdout, Error, Read, Write },
 	process::ExitCode,
 	vec::Vec
 };
@@ -38,7 +38,7 @@ fn oserr(s: &str, e: Error) -> ExitCode {
 }
 
 fn usage(s: &str) -> ExitCode {
-	eprintln!("Usage: {} [-f] [-w word_size]", s);
+	eprintln!("Usage: {} [-w word_size]", s);
 	ExitCode::from(EX_USAGE as u8)
 }
 
@@ -48,12 +48,11 @@ fn main() -> ExitCode {
 	let mut input = stdin();
 	let mut output = stdout().lock();
 
-	let mut force = false;
+	let mut optind: usize = 1;   // argv[0]
-	let mut wordsize: usize = 2;
+	let mut wordsize: usize = 2; // Equivalent to dd(1p).
 
-	while let Some(opt) = argv.getopt("fw:") {
+	while let Some(opt) = argv.getopt(":w:") {
 		match opt.opt() {
-			Ok("f") => force = true,
 			Ok("w") => {
 				if let Some(arg) = opt.arg() {
 					match arg.parse::<usize>() {
@@ -61,11 +60,16 @@ fn main() -> ExitCode {
 						_ => { return usage(&argv[0]); },
 					}
 				}
+				optind = opt.ind();
 			},
 			_ => { return usage(&argv[0]); }
 		}
 	}
 
+	if optind < argv.len() {
+		return usage(&argv[0]);
+	}
+
 	buf.resize(wordsize, 0);
 
 	loop {
@@ -83,7 +87,6 @@ fn main() -> ExitCode {
 					break oserr(&argv[0], e)
 				}
 			},
-			Err(e) if e.kind() == ErrorKind::Interrupted && force => continue,
 			Err(e) => break oserr(&argv[0], e)
 		}
 	}