fop(1): fix minor optind bug, add some comments

src/fop.rs

@@ -33,7 +33,7 @@ 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(); /* ASCII record separator */
-	let mut optind = 0;
+	let mut optind = 1;
 
 	let usage = format!(
 		"Usage: {} [-d delimiter] index command [args...]",
@@ -54,6 +54,12 @@ fn main() {
 		};
 	}
 
+	/* 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);
+	});
+
 	/* index of the argv[0] for the operator command */
 	let command_arg = optind as usize + 1;
 
@@ -63,12 +69,7 @@ fn main() {
 		exit(EX_USAGE);
 	});
 
-	/* 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);
-	});
-
+	/* 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());