[cmdline] Add "isset" command

The "isset" command can be used to determine whether or not a setting
is present.  For example:

  isset ${net0/ip} || dhcp net0   # If we have no IP address, try DHCP

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/core/exec.c b/src/core/exec.c
index 60d8cb975c70a2f9c21bae1c98c8a4ade181b731..f65a4647c588602b7c28b56e1304743375243e09 100644 (file)
--- a/src/core/exec.c
+++ b/src/core/exec.c
@@ -381,3 +381,38 @@ struct command exit_command __command = {
        .exec = exit_exec,
 };
 
+/** "isset" options */
+struct isset_options {};
+
+/** "isset" option list */
+static struct option_descriptor isset_opts[] = {};
+
+/** "isset" command descriptor */
+static struct command_descriptor isset_cmd =
+       COMMAND_DESC ( struct isset_options, isset_opts, 0, MAX_ARGUMENTS,
+                      "[...]", "" );
+
+/**
+ * "isset" command
+ *
+ * @v argc             Argument count
+ * @v argv             Argument list
+ * @ret rc             Return status code
+ */
+static int isset_exec ( int argc, char **argv ) {
+       struct isset_options opts;
+       int rc;
+
+       /* Parse options */
+       if ( ( rc = parse_options ( argc, argv, &isset_cmd, &opts ) ) != 0 )
+               return rc;
+
+       /* Return success iff any arguments exist */
+       return ( ( optind == argc ) ? -ENOENT : 0 );
+}
+
+/** "isset" command */
+struct command isset_command __command = {
+       .name = "isset",
+       .exec = isset_exec,
+};