--- coreutils/sum.c
+++ coreutils/sum.c
@@ -23,22 +23,23 @@
 //kbuild:lib-$(CONFIG_SUM) += sum.o
 
 //usage:#define sum_trivial_usage
-//usage:       "[-rs] [FILE]..."
+//usage:       "[-rsp] [FILE]..."
 //usage:#define sum_full_usage "\n\n"
 //usage:       "Checksum and count the blocks in a file\n"
 //usage:     "\n	-r	Use BSD sum algorithm (1K blocks)"
 //usage:     "\n	-s	Use System V sum algorithm (512byte blocks)"
+//usage:     "\n	-p	Print pure sum of all bytes of the file"
 
 #include "libbb.h"
 #include "common_bufsiz.h"
 
-enum { SUM_BSD, PRINT_NAME, SUM_SYSV };
+enum { SUM_BSD, SUM_SYSV, SUM_PURE };
 
 /* BSD: calculate and print the rotated checksum and the size in 1K blocks
    The checksum varies depending on sizeof (int). */
 /* SYSV: calculate and print the checksum and the size in 512-byte blocks */
 /* Return 1 if successful.  */
-static unsigned sum_file(const char *file, unsigned type)
+static unsigned sum_file(const char *file, unsigned type, unsigned print_name)
 {
 	unsigned long long total_bytes = 0;
 	int fd, r;
@@ -77,11 +78,15 @@
 		}
 	}
 
-	if (type < PRINT_NAME)
+	if (!print_name)
 		file = "";
 	if (type >= SUM_SYSV) {
-		r = (s & 0xffff) + ((s & 0xffffffff) >> 16);
-		s = (r & 0xffff) + (r >> 16);
+		if (type == SUM_PURE) {
+			s = s & 0xffffffff;
+		} else {
+			r = (s & 0xffff) + ((s & 0xffffffff) >> 16);
+			s = (r & 0xffff) + (r >> 16);
+		}
 		printf("%u %llu %s\n", s, (total_bytes + 511) / 512, file);
 	} else
 		printf("%05u %5llu %s\n", s, (total_bytes + 1023) / 1024, file);
@@ -95,23 +100,24 @@
 	unsigned n;
 	unsigned type = SUM_BSD;
 
-	n = getopt32(argv, "sr");
+	n = getopt32(argv, "srp");
 	argv += optind;
+	if (n & 4) type = SUM_PURE;
 	if (n & 1) type = SUM_SYSV;
 	/* give the bsd priority over sysv func */
 	if (n & 2) type = SUM_BSD;
 
 	if (!argv[0]) {
 		/* Do not print the name */
-		n = sum_file("-", type);
+		n = sum_file("-", type, 0);
 	} else {
 		/* Need to print the name if either
 		 * - more than one file given
-		 * - doing sysv */
-		type += (argv[1] || type == SUM_SYSV);
+		 * - doing sysv or pure sum */
+		unsigned print_name = (argv[1] || type >= SUM_SYSV);
 		n = 1;
 		do {
-			n &= sum_file(*argv, type);
+			n &= sum_file(*argv, type, print_name);
 		} while (*++argv);
 	}
 	return !n;