diff --git a/GNUmakefile b/GNUmakefile
index 64b433f..b357cd4 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -20,8 +20,9 @@ CC=cc
 CFLAGS=-O3 -Lbuild/lib -idirafter include
 
 RUSTC=rustc +nightly
-RUSTCFLAGS=-Zlocation-detail=none -Copt-level=z -Ccodegen-units=1 -Cpanic=abort 
-	-Clto=y -Cstrip=symbols -Ctarget-cpu=native
+RUSTCFLAGS=-Zlocation-detail=none -Copt-level=z -Ccodegen-units=1 \
+	-Cpanic=abort -Clto=y -Cstrip=symbols -Ctarget-cpu=native \
+	--extern sysexits=build/o/libsysexits.rlib
 
 ifeq ($(CC), gcc)
 	CFLAGS=-O3 -s -Wl,-z,noseparate-code,-z,nosectionheader -flto -Lbuild/lib \
@@ -39,7 +40,7 @@ endif
 build: build_dir false intcmp scrut str strcmp true
 
 build_dir:
-	mkdir -p build/o build/lib build/bin
+	mkdir -p build/bin build/lib build/o
 
 clean:
 	rm -rf build/
@@ -56,10 +57,16 @@ test: build
 	tests/cc-compat.sh
 	tests/posix-compat.sh
 
+sysexits: build_dir
+	bindgen --default-macro-constant-type signed \
+		"$$(printf '#include <sysexits.h>\n' | cpp -M -idirafter include - \
+		| sed 's/ /\n/g' | grep sysexits.h)" \
+		| $(RUSTC) $(RUSTCFLAGS) --crate-type lib -o build/o/libsysexits.rlib -
+
 false: src/false.rs build_dir
 	$(RUSTC) $(RUSTCFLAGS) -o build/bin/false src/false.rs
 
-fop: src/fop.rs build_dir
+fop: src/fop.rs build_dir sysexits
 	$(RUSTC) $(RUSTCFLAGS) -o build/bin/fop src/fop.rs
 
 intcmp: src/intcmp.c build_dir
@@ -76,4 +83,3 @@ strcmp: src/strcmp.c build_dir
 
 true: src/true.rs build_dir
 	$(RUSTC) $(RUSTCFLAGS) -o build/bin/true src/true.rs
-
diff --git a/src/fop.rs b/src/fop.rs
index 9c25463..287660c 100644
--- a/src/fop.rs
+++ b/src/fop.rs
@@ -18,13 +18,18 @@
 
 use std::{
 	env::args,
-	io::{ Read, stdin, Write },
+	io::{ stdin, Write },
 	process::{ Command, exit, Stdio },
 };
 
+extern crate sysexits;
+use sysexits::EX_USAGE;
+
 fn main() {
 	let argv = args().collect::<Vec<String>>();
 
+	let usage = format!("Usage: {} index command [args...]", argv[0]);
+
 	let index = match argv.get(1) {
 		Some(i) => {
 			i.parse::<usize>().unwrap_or_else(|_| {
@@ -33,18 +38,18 @@ fn main() {
 			})
 		},
 		None => {
-			eprintln!("Usage: {} index command args...", argv[0]);
-			exit(1);
+			eprintln!("{}", usage);
+			exit(EX_USAGE);
 		},
 	};
 
 	let mut buf = String::new();
-	stdin().read_to_string(&mut buf).unwrap();
+	stdin().read_line(&mut buf).unwrap();
 	let mut fields = buf.split('␞').collect::<Vec<&str>>();
 
 	argv.get(2).unwrap_or_else(|| {
-		eprintln!("Usage: {} index command args...", argv[0]);
-		exit(1);
+		eprintln!("{}", usage);
+		exit(EX_USAGE);
 	});
 
 	let opts = argv.iter().clone().skip(3).collect::<Vec<&String>>();
@@ -57,7 +62,11 @@ fn main() {
 		.unwrap();
 
 	let field = fields.get(index).unwrap_or_else(|| {
-		eprintln!("{}: {}: No such index in input.", argv[0], index.to_string());
+		eprintln!(
+			"{}: {}: No such index in input.",
+			argv[0],
+			index.to_string()
+		);
 		exit(1);
 	});