fuse_main(): extend support for printing help

There's now a way to inhibit the "usage" line (which actually got lost
in commit 225c12aebf2d), which makes it easier for simply file-systems
to generate good-looking --help output.

diff --git a/example/hello.c b/example/hello.c
index 3c24c8be3310c8dee80dd85f1f8b554b7070cc91..bf6ccf4a873a67adeb6f6d08b31a4c7b695a931e 100644 (file)
--- a/example/hello.c
+++ b/example/hello.c
@@ -42,9 +42,31 @@
 #include <string.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <stddef.h>
+#include <assert.h>
 
-static const char *hello_str = "Hello World!\n";
-static const char *hello_path = "/hello";
+/**
+ * Command line options
+ *
+ * We can't set default values for the char* fields here because
+ * fuse_opt_parse would attempt to free() them when the user specifies
+ * different values on the command line.
+ */
+static struct options {
+       const char *filename;
+       const char *contents;
+       int show_help;
+} options;
+
+#define OPTION(t, p)                           \
+    { t, offsetof(struct options, p), 1 }
+static const struct fuse_opt option_spec[] = {
+       OPTION("--name=%s", filename),
+       OPTION("--contents=%s", contents),
+       OPTION("-h", show_help),
+       OPTION("--help", show_help),
+       FUSE_OPT_END
+};
 
 static int hello_getattr(const char *path, struct stat *stbuf)
 {
@@ -54,10 +76,10 @@ static int hello_getattr(const char *path, struct stat *stbuf)
        if (strcmp(path, "/") == 0) {
                stbuf->st_mode = S_IFDIR | 0755;
                stbuf->st_nlink = 2;
-       } else if (strcmp(path, hello_path) == 0) {
+       } else if (strcmp(path+1, options.filename) == 0) {
                stbuf->st_mode = S_IFREG | 0444;
                stbuf->st_nlink = 1;
-               stbuf->st_size = strlen(hello_str);
+               stbuf->st_size = strlen(options.contents);
        } else
                res = -ENOENT;
 
@@ -77,14 +99,14 @@ static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
 
        filler(buf, ".", NULL, 0, 0);
        filler(buf, "..", NULL, 0, 0);
-       filler(buf, hello_path + 1, NULL, 0, 0);
+       filler(buf, options.filename, NULL, 0, 0);
 
        return 0;
 }
 
 static int hello_open(const char *path, struct fuse_file_info *fi)
 {
-       if (strcmp(path, hello_path) != 0)
+       if (strcmp(path+1, options.filename) != 0)
                return -ENOENT;
 
        if ((fi->flags & 3) != O_RDONLY)
@@ -98,14 +120,14 @@ static int hello_read(const char *path, char *buf, size_t size, off_t offset,
 {
        size_t len;
        (void) fi;
-       if(strcmp(path, hello_path) != 0)
+       if(strcmp(path+1, options.filename) != 0)
                return -ENOENT;
 
-       len = strlen(hello_str);
+       len = strlen(options.contents);
        if (offset < len) {
                if (offset + size > len)
                        size = len - offset;
-               memcpy(buf, hello_str + offset, size);
+               memcpy(buf, options.contents + offset, size);
        } else
                size = 0;
 
@@ -119,7 +141,41 @@ static struct fuse_operations hello_oper = {
        .read           = hello_read,
 };
 
+static void show_help(const char *progname)
+{
+       printf("usage: %s [options] <mountpoint>\n\n", progname);
+       printf("File-system specific options:\n"
+              "    --name=<s>          Name of the \"hello\" file\n"
+              "                        (default: \"hello\")\n"
+              "    --contents=<s>      Contents \"hello\" file\n"
+              "                        (default \"Hello, World!\\n\")\n"
+              "\n");
+}
+
 int main(int argc, char *argv[])
 {
-       return fuse_main(argc, argv, &hello_oper, NULL);
+       struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
+
+       /* Set defaults -- we have to use strdup so that
+          fuse_opt_parse can free the defaults if other
+          values are specified */
+       options.filename = strdup("hello");
+       options.contents = strdup("Hello World!\n");
+
+       /* Parse options */
+       if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
+               return 1;
+
+       /* When --help is specified, first print our own file-system
+          specific help text, then signal fuse_main to show
+          additional help (by adding `--help` to the options again)
+          without usage: line (by setting argv[0] to the empty
+          string) */
+       if (options.show_help) {
+               show_help(argv[0]);
+               assert(fuse_opt_add_arg(&args, "--help") == 0);
+               args.argv[0] = (char*) "";
+       }
+
+       return fuse_main(args.argc, args.argv, &hello_oper, NULL);
 }

diff --git a/include/fuse.h b/include/fuse.h
index 719623ab65978e73043928006549e8bb83cda306..894383570966b075123cc71fa29da50ca6c7ded2 100644 (file)
--- a/include/fuse.h
+++ b/include/fuse.h
@@ -608,13 +608,30 @@ struct fuse_context {
  * main() function.
  *
  * This function does the following:
- *   - parses command line options
+ *   - parses command line options, and handles --help and
+ *     --version
  *   - installs signal handlers for INT, HUP, TERM and PIPE
  *   - registers an exit handler to unmount the filesystem on program exit
  *   - creates a fuse handle
  *   - registers the operations
  *   - calls either the single-threaded or the multi-threaded event loop
  *
+ * Most file systems will have to parse some file-system specific
+ * arguments before calling this function. It is recommended to do
+ * this with fuse_opt_parse() and a processing function that passes
+ * through any unknown options (this can also be achieved by just
+ * passing NULL as the processing function). That way, the remaining
+ * options can be passed directly to fuse_main().
+ *
+ * To get a list of the options recognized by fuse_main(), look
+ * at the output when running with ``--help``.
+ *
+ * Normally, fuse_main() includes a basic ``usage: `` message in the
+ * --help output. However, if argv[0] is an empty string, the usage
+ * message is suppressed. This can be used by file systems to print
+ * their own usage line first. See hello.c for an example of how to do
+ * this.
+ *
  * Note: this is currently implemented as a macro.
  *
  * @param argc the argument counter passed to the main() function

diff --git a/lib/helper.c b/lib/helper.c
index c57edb1f66635c649c9476ae96a6451165acf574..cc5cefcdf2a29d4360e12f715e427d60259c6089 100644 (file)
--- a/lib/helper.c
+++ b/lib/helper.c
@@ -202,6 +202,9 @@ int fuse_main_real(int argc, char *argv[], const struct fuse_operations *op,
        /* Re-add --help for later processing by fuse_new()
           (that way we also get help for modules options) */
        if (opts.show_help) {
+               if(args.argv[0] != '\0')
+                       printf("usage: %s [options] <mountpoint>\n\n",
+                              args.argv[0]);
                fuse_cmdline_help();
                if (fuse_opt_add_arg(&args, "--help") == -1) {
                        res = 1;