Update

src/examples/cmp.c

+/* cat.c
+
+   Compares two files. */
+
+#include <stdio.h>
+#include <syscall.h>
+
+int
+main (int argc, char *argv[])
+{
+  int fd[2];
+
+  if (argc != 3)
+    {
+      printf ("usage: cmp A B\n");
+      return EXIT_FAILURE;
+    }
+
+  /* Open files. */
+  fd[0] = open (argv[1]);
+  if (fd[0] < 0)
+    {
+      printf ("%s: open failed\n", argv[1]);
+      return EXIT_FAILURE;
+    }
+  fd[1] = open (argv[2]);
+  if (fd[1] < 0)
+    {
+      printf ("%s: open failed\n", argv[1]);
+      return EXIT_FAILURE;
+    }
+
+  /* Compare data. */
+  for (;;)
+    {
+      int pos;
+      char buffer[2][1024];
+      int bytes_read[2];
+      int min_read;
+      int i;
+
+      pos = tell (fd[0]);
+      bytes_read[0] = read (fd[0], buffer[0], sizeof buffer[0]);
+      bytes_read[1] = read (fd[1], buffer[1], sizeof buffer[1]);
+      min_read = bytes_read[0] < bytes_read[1] ? bytes_read[0] : bytes_read[1];
+      if (min_read == 0)
+        break;
+
+      for (i = 0; i < min_read; i++)
+        if (buffer[0][i] != buffer[1][i])
+          {
+            printf ("Byte %d is %02hhx ('%c') in %s but %02hhx ('%c') in %s\n",
+                    pos + i,
+                    buffer[0][i], buffer[0][i], argv[1],
+                    buffer[1][i], buffer[1][i], argv[2]);
+            return EXIT_FAILURE;
+          }
+
+      if (min_read < bytes_read[1])
+        printf ("%s is shorter than %s\n", argv[1], argv[2]);
+      else if (min_read < bytes_read[0])
+        printf ("%s is shorter than %s\n", argv[2], argv[1]);
+    }
+
+  printf ("%s and %s are identical\n", argv[1], argv[2]);
+
+  return EXIT_SUCCESS;
+}