Stop using O_EXCL by default when opening the device for writing.

gpt.c

 /*-
  * Copyright (c) 2002 Marcel Moolenaar
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 42 matching lines @@
 #include "gpt.h"
 
 char    device_path[MAXPATHLEN];
 char    *device_name;
 
 off_t   mediasz;
 
 u_int   parts;
 u_int   secsz;
 
-int     readonly, verbose;
+int     readonly, exclusive = O_EXCL, verbose;
 
 static uint32_t crc32_tab[] = {
         0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
         0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
         0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
         0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
         0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
         0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
         0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
         0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
@@ skipping 476 matching lines @@
         free(hdr);
         return (0);
 }
 
 int
 gpt_open(const char *dev)
 {
         struct stat sb;
         int fd, mode;
 
-        mode = readonly ? O_RDONLY : O_RDWR|O_EXCL;
+        mode = readonly ? O_RDONLY : O_RDWR|exclusive;
 
         strlcpy(device_path, dev, sizeof(device_path));
         device_name = device_path;
 
         if ((fd = open(device_path, mode)) != -1)
                 goto found;
 
         snprintf(device_path, sizeof(device_path), "%s%s", _PATH_DEV, dev);
         device_name = device_path + strlen(_PATH_DEV);
         if ((fd = open(device_path, mode)) != -1)
@@ skipping 88 matching lines @@
         { cmd_show, "show" },
         { NULL, "verify" },
         { NULL, NULL }
 };
 
 static void
 usage(void)
 {
 
         fprintf(stderr,
-            "usage: %s [-rv] [-p nparts] command [options] device ...\n",
+            "usage: %s [-rSv] [-p nparts] command [options] device ...\n",
             getprogname());
         exit(1);
 }
 
 static void
 prefix(const char *cmd)
 {
         char *pfx;
         const char *prg;
 
         prg = getprogname();
         pfx = malloc(strlen(prg) + strlen(cmd) + 2);
         /* Don't bother failing. It's not important */
         if (pfx == NULL)
                 return;
 
         sprintf(pfx, "%s %s", prg, cmd);
         setprogname(pfx);
 }
 
 int
 main(int argc, char *argv[])
 {
         char *cmd, *p;
         int ch, i;
 
         /* Get the generic options */
-        while ((ch = getopt(argc, argv, "+p:rv")) != -1) {
+        while ((ch = getopt(argc, argv, "+p:rSv")) != -1) {
                 switch(ch) {
                 case 'p':
                         if (parts > 0)
                                 usage();
                         parts = strtol(optarg, &p, 10);
                         if (*p != 0 || parts < 1)
                                 usage();
                         break;
                 case 'r':
                         readonly = 1;
                         break;
+                case 'S':
+                        exclusive = 0;
+                        break;
                 case 'v':
                         verbose++;
                         break;
                 default:
                         usage();
                 }
         }
         if (!parts)
                 parts = 128;
 
         if (argc == optind)
                 usage();
 
         cmd = argv[optind++];
         for (i = 0; cmdsw[i].name != NULL && strcmp(cmd, cmdsw[i].name); i++);
 
         if (cmdsw[i].fptr == NULL)
                 errx(1, "unknown command: %s", cmd);
 
         prefix(cmd);
         return ((*cmdsw[i].fptr)(argc, argv));
 }