nshlib: Support "-f" option for command "rm"

In below two cases "rm" command with "-f" option will return 0:
  a. Bad arguments
  b. File not exists

Following "rm" of GNU coreutils 8.32

GNU coreutils
  $ rm --version
  rm (GNU coreutils) 8.32
  Copyright (C) 2020 Free Software Foundation, Inc.
  License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
  This is free software: you are free to change and redistribute it.
  There is NO WARRANTY, to the extent permitted by law.

  Written by Paul Rubin, David MacKenzie, Richard M. Stallman,
  and Jim Meyering.

  $ rm /FILE_NOT_EXISTS
  rm: cannot remove '/FILE_NOT_EXISTS': No such file or directory
  $ echo $?
  1

  $ rm -f
  $ echo $?
  0

  $ rm -f /FILE_NOT_EXISTS
  $ echo $?
  0

Without this patch
  nsh> rm
  nsh: rm: missing required argument(s)

  nsh> rm /FILE_NOT_EXISTS
  nsh: rm: unlink failed: 2
  nsh> echo $?
  1

With this patch
  nsh> rm -f
  nsh> echo $?
  0

  nsh> rm -f /FILE_NOT_EXISTS
  nsh> echo $?
  0

Signed-off-by: wangjianyu3 <[email protected]>

Author: JianyuWang0623

nshlib/nsh_command.c

@@ -505,7 +505,7 @@ static const struct cmdmap_s g_cmdmap[] =
 
 #ifdef NSH_HAVE_DIROPTS
 #  ifndef CONFIG_NSH_DISABLE_RM
-  CMD_MAP("rm",       cmd_rm,       2, 3, "[-r] <file-path>"),
+  CMD_MAP("rm",       cmd_rm,       2, 3, "[-rf] <file-path>"),
 #  endif
 #endif
 

nshlib/nsh_fscmds.c

@@ -2178,20 +2178,48 @@ static int unlink_recursive(FAR char *path, FAR struct stat *stat)
 
 int cmd_rm(FAR struct nsh_vtbl_s *vtbl, int argc, FAR char **argv)
 {
-  bool recursive = (strcmp(argv[1], "-r") == 0);
+  bool recursive = false;
+  bool force = false;
   FAR char *fullpath;
   char buf[PATH_MAX];
   struct stat stat;
   int ret = ERROR;
+  int c;
 
-  if (recursive && argc == 2)
+  while ((c = getopt(argc, argv, "rf")) != ERROR)
     {
-      nsh_error(vtbl, g_fmtargrequired, argv[0]);
-      return ret;
+      switch (c)
+        {
+          case 'r':
+            recursive = true;
+            break;
+          case 'f':
+            force = true;
+            break;
+          case '?':
+            nsh_output(vtbl, "Unknown option 0x%x\n", optopt);
+            return ret;
+          default:
+            nsh_error(vtbl, g_fmtargrequired, argv[0]);
+            return ret;
+        }
     }
 
-  fullpath = nsh_getfullpath(vtbl, recursive ? argv[2] : argv[1]);
+  if (optind >= argc)
+    {
+      if (force)
+        {
+          ret = OK;
+        }
+      else
+        {
+          nsh_error(vtbl, g_fmtargrequired, argv[0]);
+        }
 
+      return ret;
+    }
+
+  fullpath = nsh_getfullpath(vtbl, argv[optind]);
   if (fullpath != NULL)
     {
       if (recursive)
@@ -2204,6 +2232,11 @@ int cmd_rm(FAR struct nsh_vtbl_s *vtbl, int argc, FAR char **argv)
           ret = unlink(fullpath);
         }
 
+      if (force && errno == ENOENT)
+        {
+          ret = 0;
+        }
+
       if (ret < 0)
         {
           nsh_error(vtbl, g_fmtcmdfailed, argv[0], "unlink", NSH_ERRNO);