fop(1): adds functions for error handling

src/fop.rs

@@ -18,8 +18,8 @@
 
 use std::{
 	env::args,
-	io::{ Read, stdin, stdout, Write },
+	io::{ Error, Read, Write, stdin, stdout },
-	process::{ Command, exit, Stdio },
+	process::{ Command, ExitCode, Stdio, exit },
 };
 
 extern crate getopt;
@@ -34,7 +34,16 @@ use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
 #[cfg(target_os="openbsd")] extern crate openbsd;
 #[cfg(target_os="openbsd")] use openbsd::{ Promises, pledge };
 
-fn main() {
+fn err(argv0: &String, e: Error) {
+	eprintln!("{}: {}", argv0, e.strerror());
+}
+
+fn usage(argv0: &String) -> i32 {
+	eprintln!("Usage: {} [-d delimiter] index command [args...]", argv0);
+	EX_USAGE
+}
+
+fn main() -> ExitCode {
 	let argv = args().collect::<Vec<String>>();
 	let mut d = '\u{1E}'.to_string(); /* ASCII record separator */
 	let mut optind = 1;
@@ -42,16 +51,11 @@ fn main() {
 	#[cfg(target_os="openbsd")] {
 		let promises = Promises::new("stdio proc exec");
 		if let Err(e) = pledge(Some(promises), None) {
-			eprintln!("{}: {}", argv[0], e.strerror());
+			err(&argv[0], e);
 			exit(EX_OSERR);
 		}
 	}
 
-	let usage = format!(
-		"Usage: {} [-d delimiter] index command [args...]",
-		argv[0],
-	);
-
 	while let Some(opt) = argv.getopt("d:") {
 		match opt.opt() {
 			Ok("d") => {
@@ -60,8 +64,7 @@ fn main() {
 				optind = opt.ind();
 			},
 			_ => {
-				eprintln!("{}", usage);
+				return ExitCode::from(usage(&argv[0]) as u8);
-				exit(EX_USAGE);
 			}
 		};
 	}
@@ -77,14 +80,13 @@ fn main() {
 
 	/* argv[0] of the operator command */
 	let operator = argv.get(command_arg).unwrap_or_else(|| {
-		eprintln!("{}", usage);
+		exit(usage(&argv[0]));
-		exit(EX_USAGE);
 	});
 
 	/* read entire standard input into memory */
 	let mut buf = String::new();
 	if let Err(e) = stdin().read_to_string(&mut buf) {
-		eprintln!("{}: {}", argv[0], e.strerror());
+		err(&argv[0], e);
 		exit(EX_IOERR);
 	};
 
@@ -105,17 +107,13 @@ fn main() {
 		.stdout(Stdio::piped()) /* piped stdout to handle output ourselves */
 		.spawn()
 		.unwrap_or_else( |e| {
-			eprintln!("{}: {}: {}", argv[0], argv[command_arg], e.strerror());
+			err(&argv[0], e);
 			exit(EX_UNAVAILABLE);
 		});
 
 	/* get field we want to pipe into spawned program */
 	let field = fields.get(index).unwrap_or_else(|| {
-		eprintln!(
+		eprintln!("{}: {}: no such index in input", argv[0], index);
-			"{}: {}: No such index in input",
-			argv[0],
-			index.to_string(),
-		);
 		exit(EX_DATAERR);
 	});
 
@@ -126,7 +124,7 @@ fn main() {
 	}
 
 	let output = spawned.wait_with_output().unwrap_or_else(|e| {
-		eprintln!("{}: {}: {}", argv[0], argv[command_arg], e.strerror());
+		err(&argv[0], e);
 		exit(EX_IOERR);
 	});
 
@@ -143,7 +141,7 @@ fn main() {
 
 	/* convert the output of the program to UTF-8 */
 	let new_field = String::from_utf8(replace).unwrap_or_else(|e| {
-		eprintln!("{}: {}: {}", argv[0], argv[command_arg], e);
+		eprintln!("{}: {}", argv[0], e);
 		exit(EX_IOERR);
 	});
 
@@ -154,7 +152,9 @@ fn main() {
 	stdout().write_all(
 		fields.join(&d.to_string()).as_bytes()
 	).unwrap_or_else(|e| {
-		eprintln!("{}: {}", argv[0], e.strerror());
+		err(&argv[0], e);
 		exit(EX_IOERR);
 	});
+
+	ExitCode::SUCCESS
 }