Pipe qrexec-client(-vm) --help output to stdout

agent/qrexec-client-vm.c

@@ -112,19 +112,21 @@
 };
 
 _Noreturn static void usage(const char *argv0, int status) {
-    fprintf(stderr,
+    FILE *stream = status ? stderr : stdout;
+    fprintf(stream,
             "usage: %s [options] target_vmname program_ident [local_program [local program arguments]]\n",
             argv0);
-    fprintf(stderr, "Options:\n");
-    fprintf(stderr, "  -h, --help - print this message\n");
-    fprintf(stderr, "  --buffer-size=BUFFER_SIZE - minimum vchan buffer size (default: 64k)\n");
-    fprintf(stderr, "  -t, --filter-escape-chars-stdout - filter non-ASCII and control characters on stdout (default if stdout is a terminal)\n");
-    fprintf(stderr, "  -T, --filter-escape-chars-stderr - filter non-ASCII and control characters on stderr (default if stderr is a terminal)\n");
-    fprintf(stderr, "  --no-filter-escape-chars-stdout - opposite to --filter-escape-chars-stdout\n");
-    fprintf(stderr, "  --no-filter-escape-chars-stderr - opposite to --filter-escape-chars-stderr\n");
-    fprintf(stderr, "  --agent-socket=PATH - path to connect to, default: %s\n", QREXEC_AGENT_TRIGGER_PATH);
-    fprintf(stderr, "  -p PREFIX-DATA, --prefix-data=PREFIX-DATA - send the given data before the provided stdin (can only be used once)\n");
-    fprintf(stderr, "  --use-stdin-socket - use fd 0 (which must be socket) for both stdin and stdout\n");
+    fprintf(stream, "Options:\n");
+    fprintf(stream, "  -h, --help - print this message\n");
+    fprintf(stream, "  --buffer-size=BUFFER_SIZE - minimum vchan buffer size (default: 64k)\n");
+    fprintf(stream, "  -t, --filter-escape-chars-stdout - filter non-ASCII and control characters on stdout (default if stdout is a terminal)\n");
+    fprintf(stream, "  -T, --filter-escape-chars-stderr - filter non-ASCII and control characters on stderr (default if stderr is a terminal)\n");
+    fprintf(stream, "  --no-filter-escape-chars-stdout - opposite to --filter-escape-chars-stdout\n");
+    fprintf(stream, "  --no-filter-escape-chars-stderr - opposite to --filter-escape-chars-stderr\n");
+    fprintf(stream, "  --agent-socket=PATH - path to connect to, default: %s\n",
+            QREXEC_AGENT_TRIGGER_PATH);
+    fprintf(stream, "  -p PREFIX-DATA, --prefix-data=PREFIX-DATA - send the given data before the provided stdin (can only be used once)\n");
+    fprintf(stream, "  --use-stdin-socket - use fd 0 (which must be socket) for both stdin and stdout\n");
     exit(status);
 }
 

daemon/qrexec-client.c

@@ -85,9 +85,10 @@
     { NULL, 0, 0, 0 },
 };
 
-_Noreturn static void usage(const char *const name)
+_Noreturn static void usage(const char *const name, int status)
 {
-    fprintf(stderr,
+    FILE *stream = status ? stderr : stdout;
+    fprintf(stream,
             "usage: %s [options] -d domain_name ["
             "-l local_prog|"
             "-c request_id,src_domain_name,src_domain_id|"
@@ -104,7 +105,7 @@
             "  --socket-dir=PATH -  directory for qrexec socket, default: %s\n"
             "  --use-stdin-socket - use fd 0 (which must be socket) for both stdin and stdout\n",
             name ? name : "qrexec-client", QREXEC_DAEMON_SOCKET_DIR);
-    exit(1);
+    exit(status);
 }
 
 static int parse_int(const char *str, const char *msg) {
@@ -173,11 +174,6 @@
     bool exit_with_code = true;
     int rc = QREXEC_EXIT_PROBLEM;
 
-    if (argc < 3) {
-        // certainly too few arguments
-        usage(argv[0]);
-    }
-
     setup_logging("qrexec-client");
 
     while ((opt = getopt_long(argc, argv, "hd:l:eEc:tTw:Wk", longopts, NULL)) != -1) {
@@ -197,7 +193,7 @@
             case 'c':
                 if (request_id != NULL) {
                     warnx("ERROR: -c passed more than once");
-                    usage(argv[0]);
+                    usage(argv[0], 1);
                 }
                 parse_connect(optarg, &request_id, &src_domain_name, &src_domain_id);
                 break;
@@ -238,11 +234,11 @@
                 break;
             case 'h':
             default:
-                usage(argv[0]);
+                usage(argv[0], 0);
         }
     }
     if (optind >= argc || !domname)
-        usage(argv[0]);
+        usage(argv[0], 1);
     remote_cmdline = argv[optind];
 
     signal(SIGPIPE, SIG_IGN);
@@ -251,18 +247,18 @@
 
     if (just_exec + (request_id != NULL) + (local_cmdline != NULL) > 1) {
         fprintf(stderr, "ERROR: only one of -e, -l, -c can be specified\n");
-        usage(argv[0]);
+        usage(argv[0], 1);
     }
 
     if ((local_cmdline != NULL) && (local_stdin_fd != 1)) {
         fprintf(stderr, "ERROR: at most one of -l and --use-stdin-socket can be specified\n");
-        usage(argv[0]);
+        usage(argv[0], 1);
     }
 
     if (strcmp(domname, "dom0") == 0 || strcmp(domname, "@adminvm") == 0) {
         if (request_id == NULL) {
             fprintf(stderr, "ERROR: when target domain is 'dom0', -c must be specified\n");
-            usage(argv[0]);
+            usage(argv[0], 1);
         }
         strncpy(svc_params.ident, request_id, sizeof(svc_params.ident) - 1);
         svc_params.ident[sizeof(svc_params.ident) - 1] = '\0';