add cmp, thanks stateless

Makefile

@@ -14,6 +14,7 @@ SRC = \
 	cat.c      \
 	chmod.c    \
 	chown.c    \
+	cmp.c      \
 	date.c     \
 	dirname.c  \
 	echo.c     \

cmp.1

@@ -0,0 +1,25 @@
+.TH CMP 1 sbase\-VERSION
+.SH NAME
+CMP \- compare two files
+.SH SYNOPSIS
+.B cmp
+.RB [ \-ls ]
+.RI file1
+.RI file2
+.SH DESCRIPTION
+.B cmp
+compares two files byte by byte. If the files differ, cmp prints the byte and
+line number at which the difference occurred.
+.P
+The status code is 0 if the files are identical, and 1 if not.  If an error
+occurred the status code is 2.
+.SH OPTIONS
+.TP
+.B \-l
+prints the byte number, and the differing bytes (in octal), for each difference.
+.TP
+.B \-s
+prints nothing, only returns status.
+.SH SEE ALSO
+.IR comm (1),
+.IR diff (1)

cmp.c

@@ -0,0 +1,63 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include "util.h"
+
+static bool lflag = false;
+static bool sflag = false;
+
+int
+main(int argc, char *argv[])
+{
+	bool same = true;
+	char c;
+	int b[2], i;
+	long line = 1, n = 1;
+	FILE *fp[2];
+
+	if((c = getopt(argc, argv, "ls")) != -1)
+		switch(c) {
+		case 'l':
+			lflag = true;
+			break;
+		case 's':
+			sflag = true;
+			break;
+		default:
+			exit(2);
+		}
+	if(optind != argc-2) {
+		eprintf("usage: %s [-ls] file1 file2\n", argv[0]);
+		exit(2);
+	}
+	for(i = 0; i < 2; i++)
+		if(!(fp[i] = fopen(argv[optind+i], "r"))) {
+			eprintf("fopen %s:", argv[optind+i]);
+			exit(2);
+		}
+	for(n = 1; ((b[0] = getc(fp[0])) != EOF) | ((b[1] = getc(fp[1])) != EOF); n++) {
+		if(b[0] == '\n')
+			line++;
+		if(b[0] == b[1])
+			continue;
+		for(i = 0; i < 2; i++)
+			if(b[i] == EOF) {
+				fprintf(stderr, "cmp: EOF on %s\n", argv[optind+i]);
+				return 1;
+			}
+		if(!lflag) {
+			if(!sflag)
+				printf("%s %s differ: char %ld, line %ld\n",
+				       argv[optind], argv[optind+1], n, line);
+			return 1;
+		}
+		else {
+			printf("%4ld %3o %3o\n", n, b[0], b[1]);
+			same = false;
+		}
+	}
+	return same ? 0 : 1;
+}