NSH: Add readlink command.

nshlib/Kconfig

@@ -1,4 +1,5 @@
 #
+#
 # For a description of the syntax of this configuration file,
 # see the file kconfig-language.txt in the NuttX tools repository.
 #
@@ -318,7 +319,8 @@ config NSH_DISABLE_LOSMART
 
 config NSH_DISABLE_LN
 	bool "Disable ln"
-	default n
+	default y if DEFAULT_SMALL
+	default n if !DEFAULT_SMALL
 	depends on PSEUDOFS_SOFTLINKS
 
 config NSH_DISABLE_LS
@@ -434,6 +436,12 @@ config NSH_DISABLE_PWD
 	bool "Disable pwd"
 	default n
 
+config NSH_DISABLE_READLINK
+	bool "Disable readlink"
+	default y if DEFAULT_SMALL
+	default n if !DEFAULT_SMALL
+	depends on PSEUDOFS_SOFTLINKS
+
 config NSH_DISABLE_REBOOT
 	bool "Disable reboot"
 	default n if !DEFAULT_SMALL && !BOARDCTL_POWEROFF

nshlib/README.txt

@@ -947,6 +947,10 @@ o pwd
     /dev
     nsh>
 
+o readlink <link>
+
+  Show target of a soft link.
+
 o reboot
 
   Reset and reboot the system immediately.  This command depends on hardware
@@ -1228,6 +1232,7 @@ Command Dependencies on Configuration Settings
   ps         CONFIG_FS_PROCFS && !CONFIG_FS_PROCFS_EXCLUDE_PROC
   put        CONFIG_NET && CONFIG_NET_UDP && CONFIG_NFILE_DESCRIPTORS > 0 && MTU >= 558 (see note 1,2)
   pwd        !CONFIG_DISABLE_ENVIRON && CONFIG_NFILE_DESCRIPTORS > 0
+  readlink   CONFIG_NFILE_DESCRIPTORS > 0 && CONFIG_PSEUDOFS_SOFTLINK
   reboot     CONFIG_BOARDCTL_RESET
   rm         (((!CONFIG_DISABLE_MOUNTPOINT && CONFIG_FS_WRITABLE) || !CONFIG_DISABLE_PSEUDOFS_OPERATIONS) && CONFIG_NFILE_DESCRIPTORS > 0)
   rmdir      (((!CONFIG_DISABLE_MOUNTPOINT && CONFIG_FS_WRITABLE) || !CONFIG_DISABLE_PSEUDOFS_OPERATIONS) && CONFIG_NFILE_DESCRIPTORS > 0)
@@ -1278,13 +1283,13 @@ also allow it to squeeze into very small memory footprints.
   CONFIG_NSH_DISABLE_MW,        CONFIG_NSH_DISABLE_MV,        CONFIG_NSH_DISABLE_NFSMOUNT,
   CONFIG_NSH_DISABLE_NSLOOKUP,  CONFIG_NSH_DISABLE_PASSWD,    CONFIG_NSH_DISABLE_PING,
   CONFIG_NSH_DISABLE_PING6,     CONFIG_NSH_DISABLE_POWEROFF,  CONFIG_NSH_DISABLE_PS,
-  CONFIG_NSH_DISABLE_PUT,       CONFIG_NSH_DISABLE_PWD,       CONFIG_NSH_DISABLE_REBOOT,
+  CONFIG_NSH_DISABLE_PUT,       CONFIG_NSH_DISABLE_PWD,       CONFIG_NSH_DISABLE_READLINK,
-  CONFIG_NSH_DISABLE_RM,        CONFIG_NSH_DISABLE_RMDIR,     CONFIG_NSH_DISABLE_SET,
+  CONFIG_NSH_DISABLE_REBOOT,    CONFIG_NSH_DISABLE_RM,        CONFIG_NSH_DISABLE_RMDIR,
-  CONFIG_NSH_DISABLE_SH,        CONFIG_NSH_DISABLE_SHUTDOWN,  CONFIG_NSH_DISABLE_SLEEP,
+  CONFIG_NSH_DISABLE_SET,       CONFIG_NSH_DISABLE_SH,        CONFIG_NSH_DISABLE_SHUTDOWN,
-  CONFIG_NSH_DISABLE_TEST,      CONFIG_NSH_DIABLE_TIME,       CONFIG_NSH_DISABLE_UMOUNT,
+  CONFIG_NSH_DISABLE_SLEEP,     CONFIG_NSH_DISABLE_TEST,      CONFIG_NSH_DIABLE_TIME,
-  CONFIG_NSH_DISABLE_UNSET,     CONFIG_NSH_DISABLE_URLDECODE, CONFIG_NSH_DISABLE_URLENCODE,
+  CONFIG_NSH_DISABLE_UMOUNT,    CONFIG_NSH_DISABLE_UNSET,     CONFIG_NSH_DISABLE_URLDECODE,
-  CONFIG_NSH_DISABLE_USERADD,   CONFIG_NSH_DISABLE_USERDEL,   CONFIG_NSH_DISABLE_USLEEP,
+  CONFIG_NSH_DISABLE_URLENCODE, CONFIG_NSH_DISABLE_USERADD,   CONFIG_NSH_DISABLE_USERDEL,
-  CONFIG_NSH_DISABLE_WGET,      CONFIG_NSH_DISABLE_XD
+  CONFIG_NSH_DISABLE_USLEEP,    CONFIG_NSH_DISABLE_WGET,      CONFIG_NSH_DISABLE_XD
 
 Verbose help output can be suppressed by defining CONFIG_NSH_HELP_TERSE.  In that
 case, the help command is still available but will be slightly smaller.

nshlib/nsh.h

@@ -1017,6 +1017,9 @@ int cmd_lsmod(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv);
 #  if defined(CONFIG_RAMLOG_SYSLOG) && !defined(CONFIG_NSH_DISABLE_DMESG)
       int cmd_dmesg(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv);
 #  endif
+#  if !defined(CONFIG_NSH_DISABLE_READLINK) && defined(CONFIG_PSEUDOFS_SOFTLINKS)
+      int cmd_readlink(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv);
+#  endif
 #  if CONFIG_NFILE_STREAMS > 0 && !defined(CONFIG_NSH_DISABLESCRIPT)
 #     ifndef CONFIG_NSH_DISABLE_SH
        int cmd_sh(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv);

nshlib/nsh_command.c

@@ -410,6 +410,12 @@ static const struct cmdmap_s g_cmdmap[] =
 # endif
 #endif
 
+#if CONFIG_NFILE_DESCRIPTORS > 0
+#  if !defined(CONFIG_NSH_DISABLE_READLINK) && defined(CONFIG_PSEUDOFS_SOFTLINKS)
+  { "readlink", cmd_readlink, 2, 2, "<link>" },
+# endif
+#endif
+
 #if defined(CONFIG_BOARDCTL_RESET) && !defined(CONFIG_NSH_DISABLE_REBOOT)
   { "reboot",   cmd_reboot,   1, 1, NULL },
 #endif

nshlib/nsh_fscmds.c

@@ -1542,6 +1542,41 @@ errout_with_oldpath:
 #endif
 #endif
 
+/****************************************************************************
+ * Name: cmd_readlink
+ ****************************************************************************/
+
+#if CONFIG_NFILE_DESCRIPTORS > 0
+#  if !defined(CONFIG_NSH_DISABLE_READLINK) && defined(CONFIG_PSEUDOFS_SOFTLINKS)
+int cmd_readlink(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
+{
+  FAR char *fullpath;
+  ssize_t len;
+
+  /* readlink <link> */
+  /* Get the fullpath to the directory */
+
+  fullpath = nsh_getfullpath(vtbl, argv[1]);
+  if (!fullpath)
+    {
+      return ERROR;
+    }
+
+  len = readlink(fullpath, vtbl->iobuffer, IOBUFFERSIZE);
+  nsh_freefullpath(fullpath);
+
+  if (len < 0)
+    {
+      nsh_output(vtbl, g_fmtcmdfailed, "ls", "readlink", NSH_ERRNO);
+      return ERROR;
+    }
+
+  nsh_output(vtbl, "%s\n", vtbl->iobuffer);
+  return OK;
+}
+#endif
+#endif
+
 /****************************************************************************
  * Name: cmd_rm
  ****************************************************************************/