"env grep" - add options to grep in name, value, or both.

Add options to "env grep" command:

-n : search only the envrironment variable names
-v : search only their values
-b : search both names and values (= default)

An option "--" will stop parsing options, so to print variables that
contain the striing "- " please use:

	env grep -- "- "

Or to print all environment varioables which have a '-' in their name,
use:

	env grep -n -- -

Signed-off-by: Wolfgang Denk <wd@denx.de>

common/cmd_nvedit.c

@@ -165,13 +165,39 @@ static int do_env_grep(cmd_tbl_t *cmdtp, int flag,
 		       int argc, char * const argv[])
 {
 	char *res = NULL;
-	int len;
+	int len, grep_flags;
 
 	if (argc < 2)
 		return CMD_RET_USAGE;
 
+	grep_flags = H_MATCH_BOTH;
+
+	while (argc > 1 && **(argv + 1) == '-') {
+		char *arg = *++argv;
+
+		--argc;
+		while (*++arg) {
+			switch (*arg) {
+			case 'n':		/* grep for name */
+				grep_flags = H_MATCH_KEY;
+				break;
+			case 'v':		/* grep for value */
+				grep_flags = H_MATCH_DATA;
+				break;
+			case 'b':		/* grep for both */
+				grep_flags = H_MATCH_BOTH;
+				break;
+			case '-':
+				goto DONE;
+			default:
+				return CMD_RET_USAGE;
+			}
+		}
+	}
+
+DONE:
 	len = hexport_r(&env_htab, '\n',
-			flag | H_MATCH_BOTH | H_MATCH_SUBSTR,
+			flag | grep_flags | H_MATCH_SUBSTR,
 			&res, 0, argc, argv);
 
 	if (len > 0) {
@@ -1127,7 +1153,7 @@ static char env_help_text[] =
 	"env flags - print variables that have non-default flags\n"
 #endif
 #if defined(CONFIG_CMD_GREPENV)
-	"env grep string [...] - search environment\n"
+	"env grep [-n | -v | -b] string [...] - search environment\n"
 #endif
 #if defined(CONFIG_CMD_IMPORTENV)
 	"env import [-d] [-t | -b | -c] addr [size] - import environment\n"
@@ -1174,8 +1200,10 @@ U_BOOT_CMD_COMPLETE(
 U_BOOT_CMD_COMPLETE(
 	grepenv, CONFIG_SYS_MAXARGS, 0,  do_env_grep,
 	"search environment variables",
-	"string ...\n"
-	"    - list environment name=value pairs matching 'string'",
+	"[-n | -v | -b] string ...\n"
+	"    - list environment name=value pairs matching 'string'\n"
+	"      \"-n\": search variable names; \"-v\": search values;\n"
+	"      \"-b\": search both names and values (default)",
 	var_complete
 );
 #endif