fop(1): adds more comments

src/fop.rs

@@ -32,8 +32,8 @@ use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
 
 fn main() {
 	let argv = args().collect::<Vec<String>>();
-	let mut d = '\u{1E}'.to_string();
+	let mut d = '\u{1E}'.to_string(); /* ASCII record separator */
-	let mut index_arg = 0;
+	let mut optind = 0;
 
 	let usage = format!(
 		"Usage: {} [-d delimiter] index command [args...]",
@@ -43,10 +43,9 @@ fn main() {
 	while let Some(opt) = argv.getopt("d:") {
 		match opt.opt() {
 			Ok(_) => {
-				/* unwrap because Err(OptError::MissingArg) will be returned if
+				/* delimiter */
-				 * opt.arg() is None */
 				d = opt.arg().unwrap();
-				index_arg = opt.ind();
+				optind = opt.ind();
 			},
 			Err(_) => {
 				eprintln!("{}", usage);
@@ -55,38 +54,46 @@ fn main() {
 		};
 	}
 
-	let command_arg = index_arg as usize + 1;
+	/* index of the argv[0] for the operator command */
+	let command_arg = optind as usize + 1;
 
-	argv.get(command_arg).unwrap_or_else(|| {
+	/* argv[0] of the operator command */
+	let operator = argv.get(command_arg).unwrap_or_else(|| {
 		eprintln!("{}", usage);
 		exit(EX_USAGE);
 	});
 
-	let index = argv[index_arg].parse::<usize>().unwrap_or_else(|e| {
+	/* parse the specified index as a number we can use */
+	let index = argv[optind].parse::<usize>().unwrap_or_else(|e| {
 		eprintln!("{}: {}: {}", argv[0], argv[1], e);
 		exit(EX_DATAERR);
 	});
 
 	let mut buf = String::new();
 	let _ = stdin().read_to_string(&mut buf);
+
+	/* split the buffer by the delimiter (by default, '\u{1E}') */
 	let mut fields = buf.split(&d).collect::<Vec<&str>>();
 
+	/* collect arguments for the operator command */
 	let opts = argv
 		.iter()
 		.clone()
-		.skip(command_arg + 1)
+		.skip(command_arg + 1) /* skip the command name */
 		.collect::<Vec<&String>>();
 
-	let mut spawned = Command::new(argv.get(command_arg).unwrap())
+	/* spawn the command to operate on the field */
-		.args(opts)
+	let mut spawned = Command::new(operator)
+		.args(opts) /* spawn with the specified arguments */
 		.stdin(Stdio::piped())
-		.stdout(Stdio::piped())
+		.stdout(Stdio::piped()) /* piped stdout to handle output ourselves */
 		.spawn()
 		.unwrap_or_else( |e| {
 			eprintln!("{}: {}: {}", argv[0], argv[command_arg], e.strerror());
 			exit(EX_UNAVAILABLE);
 		});
 
+	/* get field we want to pipe into spawned program */
 	let field = fields.get(index).unwrap_or_else(|| {
 		eprintln!(
 			"{}: {}: No such index in input",
@@ -96,9 +103,10 @@ fn main() {
 		exit(EX_DATAERR);
 	});
 
+	/* get the stdin of the newly spawned program and feed it the field val */
 	if let Some(mut child_stdin) = spawned.stdin.take() {
 		let _ = child_stdin.write_all(field.as_bytes());
-		drop(child_stdin);
+		drop(child_stdin); /* stay safe! drop your children! */
 	}
 
 	let output = spawned.wait_with_output().unwrap_or_else(|e| {
@@ -106,17 +114,22 @@ fn main() {
 		exit(EX_IOERR);
 	});
 
+	/* get the output with which the original field will be replaced */
 	let mut replace = output.stdout.clone();
 
+	/* as long as it’s not a newline, set the replacement to the output */
 	if replace.pop() != Some(b'\n') { replace = output.stdout; }
 
+	/* 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);
 		exit(EX_IOERR);
 	});
 
+	/* store the new field in the old fields vector */
 	fields[index] = &new_field;
 
+	/* fop it */ 
 	stdout().write_all(
 		fields.join(&d.to_string()).as_bytes()
 	).unwrap_or_else(|e| {