From: Florent Monnier <blue_prawn () mageia.org>
Date: Tue, 24 Dec 2013 12:33:36 +0100
Subject: add --color option to md5sum and shaXsum

* add --color option to md5sum and shaXsum
  takes action only if stdout is a tty.
diff -Naur coreutils-8.22/src/md5sum.c coreutils-8.22-sum-color/src/md5sum.c
--- coreutils-8.22/src/md5sum.c	2013-12-04 15:48:30.000000000 +0100
+++ coreutils-8.22-sum-color/src/md5sum.c	2013-12-24 13:02:42.593519641 +0100
@@ -20,6 +20,8 @@
 
 #include <getopt.h>
 #include <sys/types.h>
+#include <stdio.h>
+#include <unistd.h>
 
 #include "system.h"
 
@@ -136,7 +138,8 @@
   STATUS_OPTION = CHAR_MAX + 1,
   QUIET_OPTION,
   STRICT_OPTION,
-  TAG_OPTION
+  TAG_OPTION,
+  COLOR_OPTION
 };
 
 static struct option const long_options[] =
@@ -146,6 +149,7 @@
   { "quiet", no_argument, NULL, QUIET_OPTION },
   { "status", no_argument, NULL, STATUS_OPTION },
   { "text", no_argument, NULL, 't' },
+  { "color", no_argument, NULL, COLOR_OPTION },
   { "warn", no_argument, NULL, 'w' },
   { "strict", no_argument, NULL, STRICT_OPTION },
   { "tag", no_argument, NULL, TAG_OPTION },
@@ -154,6 +158,35 @@
   { NULL, 0, NULL, 0 }
 };
 
+#define CODCOL_BRIGHT "0"
+
+struct color {
+  int r;
+  int g;
+  int b;
+  const char *code;
+};
+
+static struct color const colors[] =
+{
+  {255,   0,   0, "31"},
+  {  0, 255,   0, "32"},
+  {255, 255,   0, "33"},
+  {  0,   0, 255, "34"},
+  {255,   0, 255, "35"},
+  {  0, 255, 255, "36"},
+};
+
+unsigned int square_dist(
+    const struct color *c1,
+    const struct color *c2)
+{
+  int xd = c2->r - c1->r;
+  int yd = c2->g - c1->g;
+  int zd = c2->b - c1->b;
+  return (xd * xd + yd * yd + zd * zd);
+}
+
 void
 usage (int status)
 {
@@ -184,6 +217,9 @@
       fputs (_("\
       --tag            create a BSD-style checksum\n\
 "), stdout);
+      fputs (_("\
+      --color          print with colors\n\
+"), stdout);
       if (O_BINARY)
         fputs (_("\
   -t, --text           read in text mode (default if reading tty stdin)\n\
@@ -693,6 +729,7 @@
   /* Make sure bin_buffer is properly aligned. */
   unsigned char *bin_buffer = ptr_align (bin_buffer_unaligned, DIGEST_ALIGN);
   bool do_check = false;
+  bool do_color = false;
   int opt;
   bool ok = true;
   int binary = -1;
@@ -745,6 +782,9 @@
         prefix_tag = true;
         binary = 1;
         break;
+      case COLOR_OPTION:
+        do_color = true;
+        break;
       case_GETOPT_HELP_CHAR;
       case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
       default:
@@ -847,15 +887,34 @@
                   fputs (") = ", stdout);
                 }
 
-              size_t i;
+              size_t i, j, k;
 
               /* Output a leading backslash if the file name contains
                  a newline or backslash.  */
               if (!prefix_tag && needs_escape)
                 putchar ('\\');
 
-              for (i = 0; i < (digest_hex_bytes / 2); ++i)
-                printf ("%02x", bin_buffer[i]);
+              if (!do_color || !isatty (fileno(stdout))) {
+                for (i = 0; i < (digest_hex_bytes / 2); ++i)
+                  printf ("%02x", bin_buffer[i]);
+              } else {
+                for (i = 0, j = 0; i < (digest_hex_bytes / (2*3)); ++i) {
+                  struct color c;
+                  unsigned int m, n, col;
+                  c.r = bin_buffer[j++];
+                  c.g = bin_buffer[j++];
+                  c.b = bin_buffer[j++];
+                  for (k = 0, n = 0, m = 195076; k < 6; ++k) {
+                    unsigned int n = square_dist(&colors[k], &c);
+                    if (n < m) { m = n; col = k; }
+                  }
+                  printf ("\x1B[%s;1m%02x%02x%02x\x1B[0m",
+                          colors[col].code, c.r, c.g, c.b);
+                }
+                for (; j < (digest_hex_bytes / 2); ++j)
+                  printf ("\x1B[%s;1m%02x\x1B[0m",
+                          CODCOL_BRIGHT, bin_buffer[j]);
+              }
 
               if (!prefix_tag)
                 {