diff --git a/src/pg.c b/src/pg.c
index 4bcf0a0..dfa21f9 100644
--- a/src/pg.c
+++ b/src/pg.c
@@ -24,18 +24,14 @@
 #include <string.h> /* strchr(3), strcmp(3), strerror(3), strtok(3) */
 #include <unistd.h> /* getopt(3) */
 
-#if !defined EX_OK || !defined EX_SOFTWARE || !defined EX_USAGE 
-#	include <sysexits.h>
-#endif
+/* Commands start with cmd_. They take an argc and NULL-terminated argv, like
+ * main, and return a status from <sysexits.h>. Return values other than EX_OK
+ * and EX_USAGE cause pg(1) to exit with that value, except EX_UNAVAILABLE,
+ * which causes pg(1) to exit with the status EX_OK. */
+#include <sysexits.h>
 
 #define CMDLINE_MAX 99+1 /* Maximum length of command line. */
 
-/* Done while looking at plan9ports' src/cmd/p.c.
- * Taken from plan9 are the interface (minus p(1)'s shell escaping and the
- * ability to page multiple files) and the practice of reading /dev/tty to get
- * keyboard input without going through stdin. Also, a newline is now printed
- * before querying the keyboard. */
-
 static char *whitespace = " \n\r\t\v";
 
 static struct {
@@ -44,13 +40,8 @@ static struct {
 } default_page_unit = { 22, LINES } /* Plan 9 default */;
 static FILE *input;
 static char *prompt = ": ";
-
 static char *program_name = "pg";
 
-/* Commands start with cmd_. They take an argc and NULL-terminated argv, like
- * main, and return one of the following RET_ enums as a status. */
-enum{ RET_OK, RET_REQSHUTDOWN, RET_USAGE, RET_NOCMD, RET_SOFTWARE };
-
 /* Page at most l bytes from f without consideration of a buffer (print them to
  * stdout). */
 static int pg_b_u(FILE *f, size_t l){
@@ -75,21 +66,21 @@ static int pg_l_u(FILE *f, size_t l, char nl){
 	return c;
 }
 
-static int cmd_quit(int argc, char **argv){ return RET_REQSHUTDOWN; }
+static int cmd_quit(int argc, char **argv){ return EX_UNAVAILABLE; }
 static int cmd_default_page(int argc, char **argv){
 
 	if(argc > 1) /* This shouldn't be possible. */
-		return RET_USAGE;
+		return EX_USAGE;
 	if(default_page_unit.type == BYTES)
 		return pg_b_u(input, default_page_unit.quantity) == EOF
-			? RET_REQSHUTDOWN
-			: RET_OK;
+			? EX_UNAVAILABLE
+			: EX_OK;
 	else if(default_page_unit.type == LINES)
 		return pg_l_u(input, default_page_unit.quantity, '\n') == EOF
-			? RET_REQSHUTDOWN
-			: RET_OK;
+			? EX_UNAVAILABLE
+			: EX_OK;
 	else
-		return RET_SOFTWARE;
+		return EX_SOFTWARE;
 }
 static int cmd_page_down_lines(int argc, char **argv){
 
@@ -99,12 +90,12 @@ static int cmd_page_down_lines(int argc, char **argv){
 	case 2: /* not implemented */
 	default:
 		fprintf(stderr, "Usage: %s" /*" (lines)"*/ "\n", argv[0]);
-		return RET_USAGE;
+		return EX_USAGE;
 	}
 }
 
 /* A CmdMap must be NULL-terminated. */
-static struct CmdMap{ char *name; int (*fn)(int, char **); } cmd_map[] = {
+static struct CmdMap{ char *name; int (*fn)(int, char **); } builtins[] = {
 	{ "", cmd_default_page },
 	{ "+", cmd_page_down_lines },
 
@@ -140,7 +131,7 @@ static int cmdline_exec(struct CmdMap *map, char *cmdline){
 			return map->fn(argc, argv);
 
 	fprintf(stderr, "%s: %s: not found\n", program_name, argv[0]);
-	return RET_NOCMD;
+	return EX_USAGE;
 }
 
 int usage(char *s){
@@ -173,7 +164,7 @@ int main(int argc, char *argv[]){
 
 	if((t = fopen("/dev/tty", "rb")) == NULL){
 		fprintf(stderr, "%s: /dev/tty: %s\n", program_name, strerror(errno));
-		return EX_SOFTWARE;
+		return EX_OSERR;
 	}
 
 	for(;;){
@@ -190,14 +181,12 @@ int main(int argc, char *argv[]){
 		if(feof(t))
 			return EX_OK;
 
-		switch(cmdline_exec(cmd_map, (char *)cmd)){
-		case RET_USAGE: case RET_NOCMD: case RET_OK:
-			break;
-		case RET_SOFTWARE:
-			return EX_SOFTWARE;
-		case RET_REQSHUTDOWN: default:
-			return EX_OK;
-		}
+		{	int r;
+			switch((r = cmdline_exec(builtins, (char *)cmd))){
+			case EX_OK: case EX_USAGE: break;
+			case EX_UNAVAILABLE: return EX_OK;
+			default: return r;
+		}	}
 	}
 
 	/* UNREACHABLE */