1.0 Overview
	1.1 Console/NSH Front End
	1.2 Command Overview
	1.3 Conditional Command Execution
	1.4 Looping
	1.5 Built-In Variables
	1.6 Current Working Directory
	1.7 Environment Variables
	1.8 NSH Start-Up Script
	2.0 Commands.
	2.1 Evaluate Expression (test)
	2.2 Add a Routing Table Entry (addroute)
	2.3 Access the ARP table (arp)
	2.4 Base64 Decode (base64dec)
	2.5 Base64 Encode (base64enc)
	2.6 Extract Base File/Directory Name (basename)
	2.7 Terminate a Loop (break)
	2.8 Concatenate Files (cat)
	2.9 Change Current Working Directory (cd)
	2.10 Compare Files (cmp)
	2.11 Copy Files (cp)
	2.12 Show or set the date and time (date)
	2.13 Copy and Convert Files (dd)
	2.14 Delete a Routing Table Entry (delroute)
	2.15 Show volume status (df)
	2.16 Extract Path to a File/Directory (dirname)
	2.17 Echo Strings and Variables (echo)
	2.18 Show Environment Variables (env)
	2.19 Execute User Code (exec)
	2.20 Exit NSH (exit)
	2.21 Set an Environment Variable (export)
	2.22 Show Memory Manager Status (free)
	2.23 Get File Via TFTP (get)
	2.24 Show Usage Command Usage (help)
	2.25 Hexadecimal Dump of File or Device (hexdump)
	2.26 Manage Network Configuration (ifconfig)
	2.27 Take a network down (ifdown)
	2.28 Bring a network up (ifup)
	2.29 Install an OS module (insmod)
	2.30 Show Interrupt Status (irqinfo)
	2.31 Send a signal to a task (kill)
	2.32 Setup/teardown the Loop Device (losetup)
	2.33 List to a File or Directory (ln)
	2.34 List Directory Contents (ls)
	2.35 Show information about installed OS modules (lsmod)
	2.36 Calculate MD5 (md5)
	2.37 Access Memory (mb, mh, and mw)
	2.38 Show Current Tasks and Threads (ps)
	2.39 Create a Directory (mkdir)
	2.40 Create a FAT File System (mkfatfs)
	2.41 Create a FIFO (mkfifo)
	2.42 Create a RAMDISK (mkrd)
	2.43 Mount a File System (mount)
	2.44 Rename a File (mv)
	2.45 Mount an NFS File System (nfsmount)
	2.46 Lookup a network address (nslookup)
	2.47 Change a User's Password (passwd)
	2.48 Shut the system down (poweroff)
	2.49 Send File Via TFTP (put)
	2.50 Show Current Working Directory (pwd)
	2.51 Show target of a link (readlink)
	2.52 Reset and reboot the system (reboot)
	2.53 Remove a File (rm)
	2.54 Remove a Directory (rmdir)
	2.55 Remove on OS Module (rmmod)
	2.56 Show routing table (route)
	2.57 Set a Variable (set)
	2.58 Execute an NSH Script (sh)
	2.59 Shut the system down (shutdown)
	2.60 Wait for Seconds (sleep)
	2.61 Start the Telnet Daemon (telnetd)
	2.62 Time execution of another command (time)
	2.63 Set the Size of a File (truncate)
	2.64 Unmount a File System (umount)
	2.65 Print system information (uname)
	2.66 Unset an Environment Variable (unset)
	2.67 URL Decode (urldecode)
	2.68 URL Encode (urlencode)
	2.69 Add a New User (useradd)
	2.70 Delete a user (userdel)
	2.71 Wait for Microseconds (usleep)
	2.72 Get File Via HTTP (wget)
	2.73 Hexadecimal Dump of Memory (xd)
	3.0 Built-In Commands
	3.1 Check Network Peer (ping/pin6)
	4.0 Configuration Settings
	4.1 Command Dependencies on Configuration Settings
	4.2 Built-In Command Dependencies on Configuration Settings
	4.3 NSH-Specific Configuration Settings
	5.0 Customizing the NuttShell
	5.1 The NSH Library and NSH Initialization
	5.2 NSH Commands
	5.3 NSH "Built-In" Applications
	5.4 Customizing NSH Initialization
	6.0 Shell Login
	6.1 Enabling Shell Logins
	6.2 Verification of Credentials
	6.3 Password Files
	6.4 Creating a Password File for a ROMFS File System
	Index

The NSH Library. The apps/nshlib sub-directory contains the NuttShell (NSH) library. This library can easily to linked to produce a NSH application (See as an example apps/examples/nsh). The NSH Library provides a simple shell application for NuttX.

NSH Consoles. Using settings in the configuration file, NSH may be configured to use (1) the serial stdin/out, (2) a USB serial device (such as CDC/ACM), or (3) a telnet connection as the console. Or, perhaps even all at once since or BOTH. An indefinite number of telnet sessions are supported.

Start-Up prompt. When NSH is started, you will see the a welcome message such the following on the selected console:

NuttShell (NSH)
nsh>

USB console startup. When using a USB console, the start-up sequence differs a little: In this case, you are required to press ENTER three times. Then NSH prompt will appear as described above. This is required for the following reasons:

1. This assures that the USB connection is stable. The USB connection may be made, broken, and re-established a few times if the USB cable is not yet fully seated. Waiting for ENTER to be pressed three times assures that the connection is stable.
2. The establishment of the connection is two step process: First, the USB serial connection is made with the host PC. Then the application that uses the serial interface is started on the host. When the serial connection is established on the host, the host operating system may send several AT modem commands to the host depending upon how the host serial port is configured. By waiting for ENTER to be pressed three consecutive times, all of these modem commands will go to the bit-bucket and will not be interpreted as NSH command input.
3. Similarly, in the second step when the applications is started, there may be additional AT modem commands sent out the serial port. Most serial terminal programs will do this unless they are specifically configured to suppress the modem command output. Waiting for the ENTER input eliminates the invalid command errors from both (2) and (3).
4. Finally, if NSH did not wait for some positive indication that the serial terminal program is up and running, then the output of the NSH greeting and initial NSH prompt would be lost.

Extended Command Line Editing. By default, NuttX uses a simple command line editor that allows command entry after the nsh> and supports only the backspace key for editing. However, a more complete command line editor can be selected by setting CONFIG_NSH_CLE=y in the NuttX configuration file. When that option is selected, the following EMACS-like line editing commands are supported:

Simple, Re-directed, and Background Commands. The NuttShell (NSH) is a simple shell application. NSH supports the following commands forms:

Simple command:	<cmd>
Command with re-directed output:	<cmd> > <file> <cmd> >> <file>
Background command:	<cmd> &
Re-directed background command:	<cmd> > <file> & <cmd> >> <file> &

Where:

<cmd>	is any one of the simple commands listed later.
<file>	is the full or relative path to any writable object in the file system name space (file or character driver). Such objects will be referred to simply as files throughout this document.

nice'd Background Commands NSH executes at the mid-priority (128). Backgrounded commands can be made to execute at higher or lower priorities using nice:

[nice [-d <niceness>>]] <cmd> [> <file>|>> <file>] [&]

Where <niceness> is any value between -20 and 19 where lower (more negative values) correspond to higher priorities. The default niceness is 10.

Multiple commands per line. NSH will accept multiple commands per command line with each command separated with the semi-colon character (;).

Optional Syntax Extensions Because these features commit significant resources, they are disabled by default.

• CONFIG_NSH_CMDPARMS. If selected, then the output from commands, from file applications, and from NSH built-in commands can be used as arguments to other commands. The entity to be executed is identified by enclosing the command line in back quotes. For example,

  set FOO `myprogram $BAR`
  

  Will execute the program named myprogram passing it the value of the environment variable BAR. The value of the environment variable FOO is then set output of myprogram on stdout.

• CONFIG_NSH_ARGCAT. Support concatenation of strings with environment variables or command output. For example:

  set FOO XYZ
  set BAR 123
  set FOOBAR ABC_${FOO}_${BAR}
  

  would set the environment variable FOO to XYZ, BAR to 123 and FOOBAR to ABC_XYZ_123. If CONFIG_NSH_ARGCAT is not selected, then a slightly smaller FLASH footprint results but then also only simple environment variables like $FOO can be used on the command line.

• CONFIG_NSH_QUOTE. Enables back-slash quoting of certain characters within the command. This option is useful for the case where an NSH script is used to dynamically generate a new NSH script. In that case, commands must be treated as simple text strings without interpretation of any special characters. Special characters such as $, `, ", and others must be retained intact as part of the test string. This option is currently only available is CONFIG_NSH_ARGCAT is also selected.

An if-then[-else]-fi construct is also supported in order to support conditional execution of commands. This works from the command line but is primarily intended for use within NSH scripts (see the sh command). The syntax is as follows:

if [!] <cmd>
then
  [sequence of <cmd>]
else
  [sequence of <cmd>]
fi

Where <cmd> is a simple command. The command success value of zero is treated true; a non-zero command failure value is treated false. The test command is frequently used for comparisons.

Looping Constructs. while-do-done and until-do-done looping constructs are also supported. These work from the command line but are primarily intended for use within NSH scripts (see the sh command).

• while-do-done. Execute [sequence of <cmd>] as long as <cmd> has an exit status of zero. The syntax is as follows:

  while <cmd>
  do
    [sequence of <cmd>]
  done
  

• until-do-done Execute [sequence of <cmd>] as long as <cmd> has a non-zero exit status. The syntax is as follows:

  until <cmd>
  do
    [sequence of <cmd>]
  done
  

Where <cmd> is a simple command. The command success value of zero is treated true; a non-zero command failure value is treated false. The test command is frequently used for comparisons.

The break Command. A break command is also supported. The break command is only meaningful within the body of the a while or until loop, between the do and done tokens. If the break command is executed within the body of a loop, the loop will immediately terminate and execution will continue with the next command immediately following the done token.

1.5 Built-In Variables

$?	The result of the last simple command execution. On backgrounded commands, this variable holds only the result of spawning the background command.

cd and pwd. All path arguments to commands may be either an absolute path or a path relative to the current working directory. The current working directory is set using the cd command and can be queried either by using the pwd command or by using the echo $PWD command.

Environment Variables:

PATH	The default path in the file systems to look for executable, binary programs working directory
PWD	The current working directory
OLDPWD	The previous working directory

NSH Start-Up Script. NSH supports options to provide a start up script for NSH. In general this capability is enabled with CONFIG_NSH_ROMFSETC, but has several other related configuration options as described with the NSH-specific configuration settings. This capability also depends on:

• CONFIG_DISABLE_MOUNTPOINT not set
• CONFIG_NFILE_DESCRIPTORS > 4
• CONFIG_FS_ROMFS enabled

Default Start-Up Behavior. The implementation that is provided is intended to provide great flexibility for the use of Start-Up files. This paragraph will discuss the general behavior when all of the configuration options are set to the default values.

In this default case, enabling CONFIG_NSH_ROMFSETC will cause NSH to behave as follows at NSH startup time:

• NSH will create a read-only RAM disk (a ROM disk), containing a tiny ROMFS file system containing the following:

  `--init.d/
       `-- rcS
  

  Where rcS is the NSH start-up script.
• NSH will then mount the ROMFS file system at /etc, resulting in:

  |--dev/
  |   `-- ram0
  `--etc/
      `--init.d/
          `-- rcS
  

• By default, the contents of rcS script are:

  # Create a RAMDISK and mount it at XXXRDMOUNTPOINTXXX
  
  mkrd -m 1 -s 512 1024
  mkfatfs /dev/ram1
  mount -t vfat /dev/ram1 /tmp
  

• NSH will execute the script at /etc/init.d/rcS at start-up (before the first NSH prompt). After execution of the script, the root FS will look like:

  |--dev/
  |   |-- ram0
  |   `-- ram1
  |--etc/
  |   `--init.d/
  |       `-- rcS
  `--tmp/
  

Modifying the ROMFS Image. The contents of the /etc directory are retained in the file apps/nshlib/nsh_romfsimg.h OR, if CONFIG_NSH_ARCHROMFS is defined, include/arch/board/rcs.template). In order to modify the start-up behavior, there are three things to study:

1. Configuration Options. The additional CONFIG_NSH_ROMFSETC configuration options discussed with the other NSH-specific configuration settings.

2. tools/mkromfsimg.sh Script. The script tools/mkromfsimg.sh creates nsh_romfsimg.h. It is not automatically executed. If you want to change the configuration settings associated with creating and mounting the /tmp directory, then it will be necessary to re-generate this header file using the tools/mkromfsimg.sh script.

   The behavior of this script depends upon three things:

   • The configuration settings then installed configuration.
   • The genromfs tool (available from http://romfs.sourceforge.net).
   • The file apps/nshlib/rcS.template (OR, if CONFIG_NSH_ARCHROMFS is defined include/arch/board/rcs.template.

3. rcS.template. The file apps/nshlib/rcS.template contains the general form of the rcS file; configured values are plugged into this template file to produce the final rcS file.

NOTE: apps/nshlib/rcS.template generates the standard, default nsh_romfsimg.h file. If CONFIG_NSH_ARCHROMFS is defined in the NuttX configuration file, then a custom, board-specific nsh_romfsimg.h file residing in configs/<board>/include will be used. NOTE when the OS is configured, include/arch/board will be linked to configs/<board>/include.

All of the startup-behavior is contained in rcS.template. The role of mkromfsimg.sh is to (1) apply the specific configuration settings to rcS.template to create the final rcS, and (2) to generate the header file nsh_romfsimg.h containing the ROMFS file system image.

Further Information. See the section on Customizing the NuttShell for additional, more detailed information about the NSH start-up script and how to modify it.

Command Syntax:

[ <expression> ]
test <expression>

Synopsis. These are two alternative forms of the same command. They support evaluation of a boolean expression which sets $?. This command is used most frequently as the conditional command following the if in the if-then[-else]-fi construct.

Expression Syntax:

expression = simple-expression | !expression | expression -o expression | expression -a expression

simple-expression = unary-expression | binary-expression

unary-expression = string-unary | file-unary

string-unary = -n string | -z string

file-unary = -b file | -c file | -d file | -e file | -f file | -r file | -s file | -w file

binary-expression = string-binary | numeric-binary

string-binary = string = string | string == string | string != string

numeric-binary = integer -eq integer | integer -ge integer | integer -gt integer | integer -le integer | integer -lt integer | integer -ne integer

Command Syntax:

addroute <target> [<netmask>] <router>
addroute default <ipaddr> <interface>

Synopsis. This command adds an entry in the routing table. The new entry will map the IP address of a router on a local network (<router>) to an external network characterized by the <target> IP address and a network mask <netmask>

The netmask may also be expressed using IPv4 CIDR or IPv6 slash notation. In that case, the netmask need not be provided.

Example:

nsh> addroute addroute 11.0.0.0 255.255.255.0 10.0.0.2

which is equivalent to

nsh> addroute 11.0.0.0/24 10.0.0.2

The second form of the addroute command can be used to set the default gateway.

Command Syntax:

arp [-a <ipaddr> |-d <ipaddr> |-s <ipaddr> <hwaddr>]

Synopsis. Access the OS ARP table.

-a <ipaddr>

Will show the hardware address that the IP address <ipaddr> is mapped to.

-d <ipaddr>

Will delete the mapping for the IP address <ipaddr> from the ARP table.

-s <ipaddr> <hwaddr>

Will set (or replace) the mapping of the IP address <ipaddr> to the hardware address <hwaddr>.

Example:

nsh> arp -a 10.0.0.1
nsh: arp: no such ARP entry: 10.0.0.1

nsh> arp -s 10.0.0.1 00:13:3b:12:73:e6
nsh> arp -a 10.0.0.1
HWAddr: 00:13:3b:12:73:e6

nsh> arp -d 10.0.0.1
nsh> arp -a 10.0.0.1
nsh: arp: no such ARP entry: 10.0.0.1

Command Syntax:

base64dec [-w] [-f] <string or filepath>

Synopsis. To be provided.

Command Syntax:

base64enc [-w] [-f] <string or filepath>

Synopsis. To be provided.

Command Syntax:

basename <path> [<suffix>]

Synopsis. Extract the final string from a <path> by removing the preceding path segments and (optionally) removing any trailing <suffix>.

2.7 Terminate a Loop (break)

Command Syntax:

break

Synopsis. The break command is only meaningful within the body of the a while or until loop, between the do and done tokens. Outside of a loop, break command does nothing. If the break command is executed within the body of a loop, the loop will immediately terminate and execution will continue with the next command immediately following the done token.

2.8 Concatenate Files (cat)

Command Syntax:

cat <path> [<path> [<path> ...]]

Synopsis. This command copies and concatenates all of the files at <path> to the console (or to another file if the output is redirected).

Command Syntax:

cd [<dir-path>|-|~|..]

Synopsis. Changes the current working directory (PWD). Also sets the previous working directory environment variable (OLDPWD).

Forms:

cd <dir-path>	sets the current working directory to <dir-path>.
cd -	sets the current working directory to the previous working directory ($OLDPWD). Equivalent to cd $OLDPWD.
cd or cd ~	set the current working directory to the 'home' directory. The home directory can be configured by setting CONFIG_LIB_HOMEDIR in the configuration file. The default home directory is /.
cd ..	sets the current working directory to the parent directory.

Command Syntax:

cmp <path1> <path2>

Synopsis. Compare of the contents of the file at <path1> with the contents of the file at <path2>. Returns an indication only if the files differ.

Command Syntax:

cp <source-path> <dest-path>

Synopsis. Copy of the contents of the file at <source-path> to the location in the file system indicated by <dest-path>.

Command Syntax:

date [-s "MMM DD HH:MM:SS YYYY"]

Synopsis. Show or set the current date and time.

Only one format is used both on display and when setting the date/time: MMM DD HH:MM:SS YYYY. For example,

data -s "Sep 1 11:30:00 2011"

24-hour time is used.

Command Syntax:

dd if=<infile> of=<outfile> [bs=<sectsize>] [count=<sectors>] [skip=<sectors>]

Synopsis. Copy blocks from <infile> to <outfile>. <infile> or <outfile> may be the path to a standard file, a character device, or a block device. Examples follow:

1. Read from character device, write to regular file. This will create a new file of the specified size filled with zero.

   nsh> ls -l /dev
   /dev:
    crw-rw-rw-       0 zero
   nsh> dd if=/dev/zero of=/tmp/zeros bs=64 count=16
   nsh> ls -l /tmp
   /tmp:
    -rw-rw-rw-    1024 ZEROS
   

2. Read from character device, write to block device. This will fill the entire block device with zeros.

nsh> ls -l /dev
/dev:
 brw-rw-rw-       0 ram0
 crw-rw-rw-       0 zero
nsh> dd if=/dev/zero of=/dev/ram0

3. Read from a block device, write to a character device. This will read the entire block device and dump the contents in the bit bucket.

nsh> ls -l /dev
/dev:
 crw-rw-rw-       0 null
 brw-rw-rw-       0 ram0
nsh> dd if=/dev/ram0 of=/dev/null

Command Syntax:

delroute <target> [<netmask>]

Synopsis. The entry removed will be the first entry in the routing table that matches the external network characterized by the <target> IP address and the network mask <netmask>

The netmask may also be expressed using IPv4 CIDR or IPv6 slash notation. In that case, the netmask need not be provided.

Example:

nsh> delroute 11.0.0.0 255.255.255.0

which is equivalent to

nsh> delroute 11.0.0.0/24

Command Syntax:

df [-h]

Synopsis. Show the state of each mounted volume. As an example:

nsh> mount
  /etc type romfs
  /tmp type vfat
nsh> df
  Block  Number
  Size   Blocks     Used Available Mounted on
    64        6        6         0 /etc
   512      985        2       983 /tmp
nsh>

If CONFIG_NSH_CMDOPT_DF_H is defined in the NuttX configuration, then the df will also support an option -h which may be used to show the volume information in human readable format.

Command Syntax:

dirname <path>

Synopsis. Extract the path string leading up to the full <path> by removing the final directory or file name.

2.17 Echo Strings and Variables (echo)

Command Syntax:

echo [-n] [<string|$name> [<string|$name>...]]

Synopsis. Copy the sequence of strings and expanded environment variables to console output (or to a file if the output is re-directed).

The -n option suppresses the trailing newline character.

Command Syntax:

env

Synopsis. Show the current name-value pairs in the environment. Example:.

nsh> env
PATH=/bin

nsh> set foo bar
nsh> env
PATH=/bin
foo=bar

nsh> unset PATH
nsh> env
foo=bar

nsh>

NOTE: NSH local variables are not shown by the env command.

Command Syntax:

exec <hex-address>

Synopsis. Execute the user logic at address <hex-address>. NSH will pause until the execution unless the user logic is executed in background via exec <hex-address> &.

Command Syntax:

exit

Synopsis. Exit NSH. Only useful for the serial front end if you have started some other tasks (perhaps using the exec command) and you would like to have NSH out of the way. For the telnet front-end, exit terminates the telnet session.

Command Syntax:

export <name> [<value>]

Synopsis. The export command sets an environment variable, or promotes an NSH variable to an environment variable. As examples:

1. Using export to promote an NSH variable to an environment variable.

   nsh> env
   PATH=/bin
   
   nsh> set foo bar
   nsh> env
   PATH=/bin
   
   nsh> export foo
   nsh> env
   PATH=/bin
   foo=bar
   

   A group-wide environment variable is created with the same value as the local NSH variable; the local NSH variable is removed.

   NOTE: This behavior differs from the Bash shell. Bash would retain the local Bash variable which will shadow the environment variable of the same name and same value.

2. Using export to set an environment variable

   nsh> export dog poop
   nsh> env
   PATH=/bin
   foo=bar
   dog=poop
   

The export command is not supported by NSH unless both CONFIG_NSH_VARS=y and CONFIG_DISABLE_ENVIRONis not set.

Command Syntax:

free

Synopsis. Show the current state of the memory allocator. For example,

nsh> free
             total       used       free    largest
Mem:       4194288    1591552    2602736    2601584
nsh>

Where:

total	This is the total size of memory allocated for use by malloc in bytes.
used	This is the total size of memory occupied by chunks handed out by malloc.
free	This is the total size of memory occupied by free (not in use) chunks.
largest	Size of the largest free (not in use) chunk.

Command Syntax:

get [-b|-n] [-f <local-path>] -h <ip-address> <remote-path>

Synopsis. Copy the file at <remote-address> from the host whose IP address is identified by <ip-address>.

Other options:

-f <local-path>	The file will be saved relative to the current working directory unless <local-path> is provided.
-b|-n	Selects either binary ("octet") or text ("netascii") transfer mode. Default: text.

Command Syntax:

help [-v] [<cmd>]

Synopsis. Presents summary information about NSH commands to console.

Options:

-v	how verbose output will full command usage.
<cmd>	Show full command usage only for this command.

Command Syntax:

hexdump <file or device> [skip=<bytes>] [count=<bytes>]

Synopsis. Dump data in hexadecimal format from a file or character device.

skip=<bytes>	Will skip <bytes> number of bytes from the beginning.
count=<bytes>	Will stop after dumping <bytes> number of bytes.

The skip and count options are only available if CONFIG_NSH_CMDOPT_HEXDUMP is defined in the NuttX configuration.

Command Syntax:

ifconfig [nic_name [<ip-address>|dhcp]] [dr|gw|gateway <dr-address>] [netmask <net-mask>] [dns <dns-address>] [hw <hw-mac>]]

Synopsis. Multiple forms of the ifconfig command are supported:

1. With one or no arguments, ifconfig will shows the current configuration of the network and, perhaps, the status of Ethernet device:

   ifconfig
   ifconfig [nic_name]
   

   As an example:

   nsh> ifconfig
   eth0    HWaddr 00:18:11:80:10:06
           IPaddr:10.0.0.2 DRaddr:10.0.0.1 Mask:255.255.255.0
   

   If network statistics are enabled (CONFIG_NET_STATISTICS), then this command will also show the detailed state of network.

2. If both the network interface name and an IP address are supplied as arguments, then ifconfig will set the address of the Ethernet device:

   ifconfig nic_name ip_address
   

3. Other forms to be provided

NOTE: This commands depends upon having the procfs file system configured into the system. The procfs file system must also have been mounted with a command like:

nsh> mount -t procfs /proc

Command Syntax:

ifdown <interface>

Synopsis. Take down the interface identified by the name <interface>.

Example:

ifdown eth0

Command Syntax:

ifup <interface>

Synopsis. Bring up down the interface identified by the name <interface>.

Example:

ifup eth0

Command Syntax:

insmod <file-path> <module-name>

Synopsis. Install the loadable OS module at <file-path> as module <module-name>.

Example:

nsh> ls -l /mnt/romfs
/mnt/romfs:
 dr-xr-xr-x       0 .
 -r-xr-xr-x    9153 chardev
nsh> ls -l /dev
/dev:
 crw-rw-rw-       0 console
 crw-rw-rw-       0 null
 brw-rw-rw-       0 ram0
 crw-rw-rw-       0 ttyS0
nsh> lsmod
NAME                 INIT   UNINIT      ARG     TEXT     SIZE     DATA     SIZE
nsh> insmod /mnt/romfs/chardev mydriver
nsh> ls -l /dev
/dev:
 crw-rw-rw-       0 chardev
 crw-rw-rw-       0 console
 crw-rw-rw-       0 null
 brw-rw-rw-       0 ram0
 crw-rw-rw-       0 ttyS0
nsh> lsmod
NAME                 INIT   UNINIT      ARG     TEXT     SIZE     DATA     SIZE
mydriver         20404659 20404625        0 20404580      552 204047a8        0

Command Syntax:

irqinfo

Synopsis. Show the current count of interrupts taken on all attached interrupts.

Example:.

nsh> irqinfo
IRQ HANDLER  ARGUMENT    COUNT    RATE
  3 00001b3d 00000000        156   19.122
 15 0000800d 00000000        817  100.000
 30 00000fd5 20000018         20    2.490

Command Syntax:

kill -<signal> <pid>

Synopsis. Send the <signal> to the task identified by <pid>.

Example:

nsh> mkfifo /dev/fifo
nsh> cat /dev/fifo &
cat [2:128]
nsh> ps
PID PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK  COMMAND
  0   0 FIFO     Kthread --- Ready              00000000 Idle Task
  1 128 RR       Task    --- Running            00000000 init
  2 128 FIFO     pthread --- Waiting  Semaphore 00000000 <pthread>(51ea50)
nsh> kill -9 2
nsh> ps
PID PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK  COMMAND
  0   0 FIFO     Kthread --- Ready              00000000 Idle Task
  1 128 RR       Task    --- Running            00000000 init
nsh>

NOTE: NuttX does not support a FULL POSIX signaling system. A few standard signal names like SIGCHLD, SIGUSR1, SIGUSR2, SIGALRM, and SIGPOLL exist in the system. However, they do not have the default actions that you might expect. Rather, NuttX supports only what are referred to as POSIX real-time signals. These signals may be used to communicate with running tasks, may be use to waiting waiting tasks, etc.

Command Syntax 1:

losetup [-o <offset>] [-r] <dev-path> <file-path>

Synopsis. Setup the loop device at <dev-path> to access the file at <file-path> as a block device. In the following example a 256K file is created (dd) and losetup is used to make the file accessible as a block device. A FAT file system is created (mkfatfs) and mounted (mount). Files can then be managed on the loop-mounted file.

nsh> dd if=/dev/zero of=/tmp/image bs=512 count=512
nsh> ls -l /tmp
/tmp:
 -rw-rw-rw-   262144 IMAGE
nsh> losetup /dev/loop0 /tmp/image
nsh> ls -l /dev
/dev:
 brw-rw-rw-       0 loop0
nsh> mkfatfs /dev/loop0
nsh> mount -t vfat /dev/loop0 /mnt/example
nsh> ls -l /mnt
ls -l /mnt
/mnt:
 drw-rw-rw-       0 example/
nsh> echo "This is a test" >/mnt/example/atest.txt
nsh> ls -l /mnt/example
/mnt/example:
 -rw-rw-rw-      16 ATEST.TXT
nsh> cat /mnt/example/atest.txt
This is a test
nsh>

Command Syntax 2:

losetup d <dev-path>

Synopsis. Teardown the setup for the loop device at <dev-path>.

Command Syntax:

ln [-s] <target> <link>

Synopsis. The ln command will create a new symbolic link at <link> for the existing file or directory, <target>. This implementation is simplified for use with NuttX in these ways:

• Links may be created only within the NuttX top-level, pseudo file system. No file system currently supported by NuttX provides symbolic links.
• For the same reason, only soft links are implemented.
• File privileges are ignored.
• c_time is not updated.

Command Syntax:

ls [-lRs] <dir-path>

Synopsis. Show the contents of the directory at <dir-path>. NOTE: <dir-path> must refer to a directory and no other file system object.

Options:

-R	Show the contents of specified directory and all of its sub-directories.
-s	Show the size of the files along with the filenames in the listing
-l	Show size and mode information along with the filenames in the listing.

Command Syntax:

lsmod

Synopsis. Show information about the currently installed OS modules. This information includes:

• The module name assigned to the module when it was installed (NAME, string).
• The address of the module initialization function (INIT, hexadecimal).
• The address of the module un-initialization function (UNINIT, hexadecimal).
• An argument that will be passed to the module un-initialization function (ARG, hexadecimal).
• The start of the .text memory region (TEXT, hexadecimal).
• The size of the .text memory region size (SIZE, decimal).
• The start of the .bss/.data memory region (DATA, hexadecimal).
• The size of the .bss/.data memory region size (SIZE, decimal).

Example:

nsh> lsmod
NAME                 INIT   UNINIT      ARG     TEXT     SIZE     DATA     SIZE
mydriver         20404659 20404625        0 20404580      552 204047a8        0

Command Syntax:

md5 [-f] <string or filepath>

Synopsis. To be provided.

Command Syntax:

mb <hex-address>[=<hex-value>][ <hex-byte-count>]
mh <hex-address>[=<hex-value>][ <hex-byte-count>]
mw <hex-address>[=<hex-value>][ <hex-byte-count>]

Synopsis. Access memory using byte size access (mb), 16-bit accesses (mh), or 32-bit access (mw). In each case,

<hex-address>	Specifies the address to be accessed. The current value at that address will always be read and displayed.
<hex-address>=<hex-value>	Read the value, then write <hex-value> to the location.
<hex-byte-count>	Perform the mb, mh, or mw operation on a total of <hex-byte-count> bytes, increment the <hex-address> appropriately after each access.

Example:

nsh> mh 0 16
  0 = 0x0c1e
  2 = 0x0100
  4 = 0x0c1e
  6 = 0x0110
  8 = 0x0c1e
  a = 0x0120
  c = 0x0c1e
  e = 0x0130
  10 = 0x0c1e
  12 = 0x0140
  14 = 0x0c1e
nsh>

Command Syntax:

ps

Synopsis. Show the currently active threads and tasks. For example,

nsh> ps
PID PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK  COMMAND
  0   0 FIFO     Kthread --- Ready              00000000 Idle Task
  1 128 RR       Task    --- Running            00000000 init
  2 128 FIFO     Task    --- Waiting  Semaphore 00000000 nsh_telnetmain()
  3 100 RR       pthread --- Waiting  Semaphore 00000000 <pthread>(21)
nsh>

NOTE: This commands depends upon having the procfs file system configured into the system. The procfs file system must also have been mounted with a command like:

nsh> mount -t procfs /proc

Command Syntax:

mkdir <path>

Synopsis. Create the directory at <path>. All components of of <path> except the final directory name must exist on a mounted file system; the final directory must not.

Limited to Mounted File Systems. Recall that NuttX uses a pseudo file system for its root file system. The mkdir command can only be used to create directories in volumes set up with the mount command; it cannot be used to create directories in the pseudo file system.

Example:

nsh> mkdir /mnt/fs/tmp
nsh> ls -l /mnt/fs
/mnt/fs:
 drw-rw-rw-       0 TESTDIR/
 drw-rw-rw-       0 TMP/
nsh>

Command Syntax:

mkfatfs [-F <fatsize>] [-r <rootdirentries>] <block-driver>

Synopsis. Format a fat file system on the block device specified by <block-driver> path. The FAT size may be provided as an option. Without the <fatsize> option, mkfatfs will select either the FAT12 or FAT16 format. For historical reasons, if you want the FAT32 format, it must be explicitly specified on the command line.

The -r option may be specified to select the the number of entries in the root directory for FAT12 and FAT16 file systems. Typical values for small volumes would be 112 or 224; 512 should be used for large volumes, such as hard disks or very large SD cards. The default is 512 entries in all cases.

The reported number of root directory entries used with FAT32 is zero because the FAT32 root directory is a cluster chain.

NSH provides this command to access the mkfatfs() NuttX API. This block device must reside in the NuttX pseudo file system and must have been created by some call to register_blockdriver() (see include/nuttx/fs/fs.h).

Command Syntax:

mkfifo <path>

Synopsis. Creates a FIFO character device anywhere in the pseudo file system, creating whatever pseudo directories that may be needed to complete the <path>. By convention, however, device drivers are place in the standard /dev directory. After it is created, the FIFO device may be used as any other device driver. NSH provides this command to access the mkfifo() NuttX API.

Example

nsh> ls -l /dev
/dev:
 crw-rw-rw-       0 console
 crw-rw-rw-       0 null
 brw-rw-rw-       0 ram0
nsh> mkfifo /dev/fifo
nsh> ls -l /dev
ls -l /dev
/dev:
 crw-rw-rw-       0 console
 crw-rw-rw-       0 fifo
 crw-rw-rw-       0 null
 brw-rw-rw-       0 ram0
nsh>

Command Syntax:

mkrd [-m <minor>] [-s <sector-size>] <nsectors>

Synopsis. Create a ramdisk consisting of <nsectors>, each of size <sector-size> (or 512 bytes if <sector-size> is not specified. The ramdisk will be registered as /dev/ram<minor>. If <minor> is not specified, mkrd will attempt to register the ramdisk as /dev/ram0.

Example

nsh> ls /dev
/dev:
 console
 null
 ttyS0
 ttyS1
nsh> mkrd 1024
nsh> ls /dev
/dev:
 console
 null
 ram0
 ttyS0
 ttyS1
nsh>

Once the ramdisk has been created, it may be formatted using the mkfatfs command and mounted using the mount command.

Example

nsh> mkrd 1024
nsh> mkfatfs /dev/ram0
nsh> mount -t vfat /dev/ram0 /tmp
nsh> ls /tmp
/tmp:
nsh>

Command Syntax:

mount -t <fstype> [-o <options>] <block-device> <dir-path>

Synopsis. The mount command performs one of two different operations. If no parameters are provided on the command line after the mount command, then the mount command will enumerate all of the current mountpoints on the console.

If the mount parameters are provided on the command after the mount command, then the mount command will mount a file system in the NuttX pseudo-file system. mount performs a three way association, binding:

1. File System. The '-t <fstype>' option identifies the type of file system that has been formatted on the <block-device>. As of this writing, vfat is the only supported value for <fstype>
2. Block Device. The <block-device> argument is the full or relative path to a block driver inode in the pseudo file system. By convention, this is a name under the /dev sub-directory. This <block-device> must have been previously formatted with the same file system type as specified by <fstype>
3. Mount Point. The mount point, <dir-path>, is the location in the pseudo file system where the mounted volume will appear. This mount point can only reside in the NuttX pseudo file system. By convention, this mount point is a subdirectory under /mnt. The mount command will create whatever pseudo directories that may be needed to complete the full path but the full path must not already exist.

After the volume has been mounted in the NuttX pseudo file system, it may be access in the same way as other objects in the file system.

Examples:

Using mount to mount a file system:

nsh> ls -l /dev
/dev:
 crw-rw-rw-       0 console
 crw-rw-rw-       0 null
 brw-rw-rw-       0 ram0
nsh> ls /mnt
nsh: ls: no such directory: /mnt
nsh> mount -t vfat /dev/ram0 /mnt/fs
nsh> ls -l /mnt/fs/testdir
/mnt/fs/testdir:
 -rw-rw-rw-      15 TESTFILE.TXT
nsh> echo "This is a test" >/mnt/fs/testdir/example.txt
nsh> ls -l /mnt/fs/testdir
/mnt/fs/testdir:
-rw-rw-rw-      15 TESTFILE.TXT
 -rw-rw-rw-      16 EXAMPLE.TXT
nsh> cat /mnt/fs/testdir/example.txt
This is a test
nsh>

Using mount to enumerate mounts:

nsh> mount
  /etc type romfs
  /mnt/fs type vfat
  /tmp type vfat

Command Syntax:

mv <old-path> <new-path>

Synopsis. Rename the file object at <old-path> to <new-path>. Both paths must reside in the same mounted file system.

Command Syntax:

nfsmount <server-address> <mount-point> <remote-path>

Synopsis. Mount the remote NFS server directory<remote-path> at <mount-point> on the target machine. <server-address> is the IP address of the remote server.

Command Syntax:

nslookup <host-name>

Synopsis. Lookup and print the IP address associated with <host-name>.

Command Syntax:

passwd <username> <password>

Synopsis. Set the password for the existing user <username> to <password>.

Command Syntax:

poweroff [<n>]

Synopsis. Shutdown and power off the system immediately. This command depends on board-specific hardware support to power down the system. The optional,decimal numeric argument may be included to provide power off mode to board-specific power off logic.

NOTE: Supporting both the poweroff and shutdown commands is redundant.

Command Syntax:

put [-b|-n] [-f <remote-path>] -h <ip-address> <local-path>

Synopsis. Copy the file at <local-address> to the host whose IP address is identified by <ip-address>.

Other options:

-f <remote-path>	The file will be saved relative with the same name on the host unless <remote-path> is provided.
-b|-n	Selects either binary ("octet") or text ("netascii") transfer mode. Default: text.

Command Syntax:

pwd

Synopsis. Show the current working directory.

nsh> cd /dev
nsh> pwd
/dev
nsh>

Same as echo $PWD.

nsh> echo $PWD
/dev
nsh>

Command Syntax:

readlink <link>

Synopsis. Show the target of the soft link at the path <link>.

Command Syntax:

reboot [<n>]

Synopsis. Reset and reboot the system immediately. This command depends on hardware support to reset the system. The optional, decimal numeric argument <n> may be included to provide a reboot mode to board-specific reboot logic.

NOTE: Supporting both the reboot and shutdown commands is redundant.

Command Syntax:

rm <file-path>

Synopsis. Remove the specified <file-path> name from the mounted file system. Recall that NuttX uses a pseudo file system for its root file system. The rm command can only be used to remove (unlink) files in volumes set up with the mount command; it cannot be used to remove names in the pseudo file system.

Example:

nsh> ls /mnt/fs/testdir
/mnt/fs/testdir:
 TESTFILE.TXT
 EXAMPLE.TXT
nsh> rm /mnt/fs/testdir/example.txt
nsh> ls /mnt/fs/testdir
/mnt/fs/testdir:
 TESTFILE.TXT
nsh>

Command Syntax:

rmdir <dir-path>

Synopsis. Remove the specified <dir-path> directory from the mounted file system. Recall that NuttX uses a pseudo file system for its root file system. The rmdir command can only be used to remove directories from volumes set up with the mount command; it cannot be used to remove directories from the pseudo file system.

Example:

nsh> mkdir /mnt/fs/tmp
nsh> ls -l /mnt/fs
/mnt/fs:
 drw-rw-rw-       0 TESTDIR/
 drw-rw-rw-       0 TMP/
nsh> rmdir /mnt/fs/tmp
nsh> ls -l /mnt/fs
/mnt/fs:
 drw-rw-rw-       0 TESTDIR/
nsh>

Command Syntax:

rmmod <module-name>

Synopsis. Remove the loadable OS module with the <module-name>. NOTE: An OS module can only be removed if it is not busy.

Example:

nsh> lsmod
NAME                 INIT   UNINIT      ARG     TEXT     SIZE     DATA     SIZE
mydriver         20404659 20404625        0 20404580      552 204047a8        0
nsh> rmmod mydriver
nsh> lsmod
NAME                 INIT   UNINIT      ARG     TEXT     SIZE     DATA     SIZE
nsh>

Command Syntax:

route ipv4|ipv6

Synopsis. Show the contents of routing table for IPv4 or IPv6.

If only IPv4 or IPv6 is enabled, then the argument is optional but, if provided, must match the enabled internet protocol version.

Command Syntax:

set [{+|-}{e|x|xe|ex}] [<name> <value>]

Synopsis. Set the variable <name> to the string <value> and or set NSH parser control options.

For example, a variable may be set like this:

nsh> echo $foobar

nsh> set foobar foovalue
nsh> echo $foobar
foovalue
nsh>

If CONFIG_NSH_VARS is selected, the effect of this set command is to set the local NSH variable. Otherwise, the group-wide environment variable will be set.

NOTE: The Bash shell does not work this way. Bash would set the value of both the local Bash variable and the environment variable of the same name to the same value.

If CONFIG_NSH_VARS=y is selected and no arguments are provided, then the set command will list all of the local NSH variables.

nsh> set
foolbar=foovalue

Set the exit on error control and/or print a trace of commands when parsing scripts in NSH. The settings are in effect from the point of execution, until they are changed again, or in the case of the initialization script, the settings are returned to the default settings when it exits. Included child scripts will run with the parents settings and changes made in the child script will effect the parent on return.

• Use set -e to enable and set +e to disable (ignore) the exit condition on commands. The default is -e. Errors cause script to exit.

• Use set -x to enable and set +x to disable (silence) printing a trace of the script commands as they are executed. The default is +x: no printing of a trace of script commands as they are executed.

Example 1 - no exit on command not found

set +e
notacommand

Example 2 - will exit on command not found

set -e
notacommand

Example 3 - will exit on command not found, and print a trace of the script commands

set -ex

Example 4 - will exit on command not found, and print a trace of the script commands and set foobar to foovalue.

set -ex foobar foovalue
nsh> echo $foobar
foovalue

Command Syntax:

sh <script-path>

Synopsis. Execute the sequence of NSH commands in the file referred to by <script-path>.

Command Syntax:

shutdown [--reboot]

Synopsis. Shutdown and power off the system or, optionally, reset and reboot the system immediately. This command depends on hardware support to power down or reset the system; one, both, or neither behavior may be supported.

NOTE: The shutdown command duplicates the behavior of the poweroff and eboot commands.

Command Syntax:

sleep <sec>

Synopsis. Pause execution (sleep) for <sec> seconds.

Command Syntax:

telnetd

Synopsis. Start the Telnet daemon if it is not already running.

The Telnet daemon may be started either programmatically by calling nsh_telnetstart() or it may be started from the NSH command line using this telnetd command.

Normally this command would be suppressed with CONFIG_NSH_DISABLE_TELNETD because the Telnet daemon is automatically started in nsh_main.c. The exception is when CONFIG_NSH_NETLOCAL is selected. In that case, the network is not enabled at initialization but rather must be enabled from the NSH command line or via other applications.

In that case, when nsh_telnetstart() is called before the the network is initialized, it will fail.

Command Syntax:

time "<command>"

Synopsis. Perform command timing. This command will execute the following <command> string and then show how much time was required to execute the command. Time is shown with a resolution of 100 microseconds which may be beyond the resolution of many configurations. Note that the <command> must be enclosed in quotation marks if it contains spaces or other delimiters.

Example:

nsh> time "sleep 2"

2.0100 sec
nsh>

The additional 10 milliseconds in this example is due to the way that the sleep command works: It always waits one system clock tick longer than requested and this test setup used a 10 millisecond periodic system timer. Sources of error could include various quantization errors, competing CPU usage, and the additional overhead of the time command execution itself which is included in the total.

The reported time is the elapsed time from starting of the command to completion of the command. This elapsed time may not necessarily be just the processing time for the command. It may included interrupt level processing, for example. In a busy system, command processing could be delayed if pre-empted by other, higher priority threads competing for CPU time. So the reported time includes all CPU processing from the start of the command to its finish possibly including unrelated processing time during that interval.

Notice that:

nsh> time "sleep 2 &"
sleep [3:100]

0.0000 sec
nsh>

Since the sleep command is executed in background, the sleep command completes almost immediately. As opposed to the following where the time command is run in background with the sleep command:

nsh> time "sleep 2" &
time [3:100]
nsh>
2.0100 sec

Command Syntax:

truncate -s <length> <file-path>

Synopsis. Shrink or extend the size of the regular file at <file-path> to the specified<length>.

A <file-path> argument that does not exist is created. The <length> option is NOT optional.

If a <file-path> is larger than the specified size, the extra data is lost. If a <file-path> is shorter, it is extended and the extended part reads as zero bytes.

Command Syntax:

umount <dir-path>

Synopsis. Un-mount the file system at mount point <dir-path>. The umount command can only be used to un-mount volumes previously mounted using mount command.

Example:

nsh> ls /mnt/fs
/mnt/fs:
 TESTDIR/
nsh> umount /mnt/fs
nsh> ls /mnt/fs
/mnt/fs:
nsh: ls: no such directory: /mnt/fs
nsh>

Command Syntax:

uname [-a | -imnoprsv]

Synopsis. Print certain system information. With no options, the output is the same as -s.

-a	Print all information, in the following order, except omit -p and -i if unknown:
-s, -o	Print the operating system name (NuttX)
-n	Print the network node hostname (only available if CONFIG_NET=y)
-r	Print the kernel release
-v	Print the kernel version
-m	Print the machine hardware name
-i	Print the machine platform name
-p	Print "unknown"

Command Syntax:

unset <name>

Synopsis. Remove the value associated with the variable <name>. This will remove the name-value pair from both the NSH local variables and the group-wide environment variables. For example:

nsh> echo $foobar
foovalue
nsh> unset foobar
nsh> echo $foobar

nsh>

Command Syntax:

urldecode [-f] <string or filepath>

Synopsis. To be provided.

Command Syntax:

urlencode [-f] <string or filepath>

Synopsis. To be provided.

Command Syntax:

useradd <username> <password>

Synopsis. Add a new user with <username> and <password>.

Command Syntax:

userdel <username>

Synopsis. Delete the user with the name <username>.

Command Syntax:

usleep <usec>

Synopsis. Pause execution (sleep) of <usec> microseconds.

Command Syntax:

wget [-o <local-path>] <url>

Synopsis. Use HTTP to copy the file at <url> to the current directory.

Options:

-o <local-path>

The file will be saved relative to the current working directory and with the same name as on the HTTP server unless <local-path> is provided.

Command Syntax:

xd <hex-address> <byte-count>

Synopsis. Dump <byte-count> bytes of data from address <hex-address>.

Example:

nsh> xd 410e0 512
Hex dump:
0000: 00 00 00 00 9c 9d 03 00 00 00 00 01 11 01 10 06 ................
0010: 12 01 11 01 25 08 13 0b 03 08 1b 08 00 00 02 24 ....%..........$
...
01f0: 08 3a 0b 3b 0b 49 13 00 00 04 13 01 01 13 03 08 .:.;.I..........
nsh>

In addition to the commands that are part of NSH listed in the previous section above, there can be additional, external built-in applications that can be added to NSH. These are separately excecuble programs but will appear much like the commands that are a part of NSH. The primary difference from the user's perspective is that help information about the built-in applications is not available directly from NSH. Rather, you will need to execute the application with the -h option to get help about using the built-in applications.

There are several built-in applications in the apps/ repository. No attempt is made here to enumerate all of them. But a few of the more common, useful built-in applications are listed below.

Command Syntax:

ping  [-c <count>] [-i <interval>] <ip-address>
ping6 [-c <count>] [-i <interval>] <ip-address>

Synopsis. Test the network communication with a remote peer. Example,

nsh> ping 10.0.0.1
PING 10.0.0.1 56 bytes of data
56 bytes from 10.0.0.1: icmp_seq=1 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=2 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=3 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=4 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=5 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=6 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=7 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=8 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=9 time=0 ms
56 bytes from 10.0.0.1: icmp_seq=10 time=0 ms
10 packets transmitted, 10 received, 0% packet loss, time 10190 ms
nsh>

The availability of the above commands depends upon features that may or may not be enabled in the NuttX configuration file. The following table indicates the dependency of each command on NuttX configuration settings. General configuration settings are discussed in the NuttX Porting Guide. Configuration settings specific to NSH as discussed at the bottom of this document.

Note that in addition to general NuttX configuration settings, each NSH command can be individually disabled via the settings in the rightmost column. All of these settings make the configuration of NSH potentially complex but also allow it to squeeze into very small memory footprints.

¹ Because of hardware padding, the actual required packet size may be larger
² Special TFTP server start-up options will probably be required to permit creation of files for the correct operation of the put command.
³ CONFIG_FS_READABLE is not a user configuration but is set automatically if any readable file system is selected. At present, this is either CONFIG_FS_FAT or CONFIG_FS_ROMFS.
⁴ CONFIG_FS_WRITABLE is not a user configuration but is set automatically if any writable file system is selected. At present, this is only CONFIG_FS_FAT.
⁵ 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.

All built-in applications require that support for NSH built-in applications has been enabled. This support is enabled with CONFIG_BUILTIN=y and CONFIG_NSH_BUILTIN_APPS=y.

The behavior of NSH can be modified with the following settings in the configs/<board-name>/defconfig file:

If Telnet is selected for the NSH console, then we must configure the resources used by the Telnet daemon and by the Telnet clients.

One or both of CONFIG_NSH_CONSOLE and CONFIG_NSH_TELNET must be defined. If CONFIG_NSH_TELNET is selected, then there some other configuration settings that apply:

If you use DHCPC, then some special configuration network options are required. These include:

If CONFIG_NSH_ROMFSETC is selected, then the following additional configuration setting apply:

When the default rcS file used when CONFIG_NSH_ROMFSETC is selected, it will mount a FAT FS under /tmp. The following selections describe that FAT FS.

Overview. The NuttShell (NSH) is a simple shell application that may be used with NuttX. It supports a variety of commands and is (very) loosely based on the Bash shell and the common utilities used with Bash shell programming. The paragraphs in this appendix will focus on customizing NSH: Adding new commands, changing the initialization sequence, etc.

Overview. NSH is implemented as a library that can be found at apps/nshlib. As a library, it can be custom built into any application that follows the NSH initialization sequence described below. As an example, the code at apps/examples/nsh/nsh_main.c illustrates how to start NSH and the logic there was intended to be incorporated into your own custom code. Although code was generated simply as an example, in the end most people just use this example code as their application main() function. That initialization performed by that example is discussed in the following paragraphs.

5.1.1 NSH Initialization sequence

The NSH start-up sequence is very simple. As an example, the code at apps/examples/nsh/nsh_main.c illustrates how to start NSH. It simple does the following:

1. If you have C++ static initializers, it will call your implementation of up_cxxinitialize() which will, in turn, call those static initializers. For the case of the STM3240G-EVAL board, the implementation of up_cxxinitialize() can be found at nuttx/configs/stm3240g-eval/src/up_cxxinitialize.c.

2. This function then calls nsh_initialize() which initializes the NSH library. nsh_initialize() is described in more detail below.

3. If the Telnetconsole is enabled, it calls nsh_telnetstart() which resides in the NSH library. nsh_telnetstart() will start the Telnet daemon that will listen for Telnet connections and start remote NSH sessions.

4. If a local console is enabled (probably on a serial port), then nsh_consolemain() is called. nsh_consolemain() also resides in the NSH library. nsh_consolemain() does not return so that finished the entire NSH initialization sequence.

5.1.2 nsh_initialize()

The NSH initialization function, nsh_initialize(), be found in apps/nshlib/nsh_init.c. It does only three things:

1. nsh_romfsetc(): If so configured, it executes an NSH start-up script that can be found at /etc/init.d/rcS in the target file system. The nsh_romfsetc() function can be found in apps/nshlib/nsh_romfsetc.c. This function will (1) register a ROMFS file system, then (2) mount the ROMFS file system. /etc is the default location where a read-only, ROMFS file system is mounted by nsh_romfsetc().

   The ROMFS image is, itself, just built into the firmware. By default, this rcS start-up script contains the following logic:

   # Create a RAMDISK and mount it at XXXRDMOUNTPOINTXXX
   
   mkrd -m XXXMKRDMINORXXX -s XXMKRDSECTORSIZEXXX XXMKRDBLOCKSXXX
   mkfatfs /dev/ramXXXMKRDMINORXXX
   mount -t vfat /dev/ramXXXMKRDMINORXXX XXXRDMOUNTPOINTXXX
   

   Where the XXXX*XXXX strings get replaced in the template when the ROMFS image is created:

   • XXXMKRDMINORXXX will become the RAM device minor number. Default: 0

   • XXMKRDSECTORSIZEXXX will become the RAM device sector size

   • XXMKRDBLOCKSXXX will become the number of sectors in the device.

   • XXXRDMOUNTPOINTXXX will become the configured mount point. Default: /etc

   By default, the substituted values would yield an rcS file like:

   # Create a RAMDISK and mount it at /tmp
   
   mkrd -m 1 -s 512 1024
   mkfatfs /dev/ram1
   mount -t vfat /dev/ram1 /tmp
   

   This script will, then:

   • Create a RAMDISK of size 512*1024 bytes at /dev/ram1,

   • Format a FAT file system on the RAM disk at /dev/ram1, and then

   • Mount the FAT file system at a configured mountpoint, /tmp.

   This rcS template file can be found at apps/nshlib/rcS.template. The resulting ROMFS file system can be found in apps/nshlib/nsh_romfsimg.h.

2. board_app_initialize(): Next any architecture-specific NSH initialization will be performed (if any). For the STM3240G-EVAL, this architecture specific initialization can be found at configs/stm3240g-eval/src/stm32_appinit.c. This it does things like: (1) Initialize SPI devices, (2) Initialize SDIO, and (3) mount any SD cards that may be inserted.

3. nsh_netinit(): The nsh_netinit() function can be found in apps/nshlib/nsh_netinit.c.

Overview. NSH supports a variety of commands as part of the NSH program. All of the NSH commands are listed in the NSH documentation above. Not all of these commands may be available at any time, however. Many commands depend upon certain NuttX configuration options. You can enter the help command at the NSH prompt to see the commands actual available:

nsh> help

For example, if network support is disabled, then all network-related commands will be missing from the list of commands presented by 'nsh> help'. You can see the specific command dependencies in the table above.

5.2.1 Adding New NSH Commands

New commands can be added to the NSH very easily. You simply need to add two things:

1. The implementation of your command, and

2. A new entry in the NSH command table

Implementation of Your Command. For example, if you want to add a new a new command called mycmd to NSH, you would first implement the mycmd code in a function with this prototype:

int cmd_mycmd(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv);

The argc and argv are used to pass command line arguments to the NSH command. Command line parameters are passed in a very standard way: argv[0] will be the name of the command, and argv[1] through argv[argc-1] are the additional arguments provided on the NSH command line.

The first parameter, vtbl, is special. This is a pointer to session-specific state information. You don't need to know the contents of the state information, but you do need to pass this vtbl argument when you interact with the NSH logic. The only use you will need to make of the vtbl argument will be for outputting data to the console. You don't use printf() within NSH commands. Instead you would use:

void nsh_output(FAR struct nsh_vtbl_s *vtbl, const char *fmt, …);

So if you only wanted to output "Hello, World!" on the console, then your whole command implementation might be:

int cmd_mycmd(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
{
  nsh_output(vtbl, "Hello, World!");
  return 0;
}

The prototype for the new command should be placed in apps/examples/nshlib/nsh.h.

Adding You Command to the NSH Command Table. All of the commands support by NSH appear in a single table called:

const struct cmdmap_s g_cmdmap[]

That table can be found in the file apps/examples/nshlib/nsh_parse.c. The structure cmdmap_s is also defined in apps/nshlib/nsh_parse.c:

struct cmdmap_s
{
  const char *cmd;        /* Name of the command */
  cmd_t       handler;    /* Function that handles the command */
  uint8_t     minargs;    /* Minimum number of arguments (including command) */
  uint8_t     maxargs;    /* Maximum number of arguments (including command) */
  const char *usage;      /* Usage instructions for 'help' command */
};

This structure provides everything that you need to describe your command: Its name (cmd), the function that handles the command (cmd_mycmd()), the minimum and maximum number of arguments needed by the command, and a string describing the command line arguments. That last string is what is printed when enter "nsh> help".

So, for you sample command, you would add the following the to the g_cmdmap[] table:

{ "mycmd", cmd_mycmd, 1, 1, NULL },

This entry is particularly simply because mycmd is so simple. Look at the other commands in g_cmdmap[] for more complex examples.

Overview. In addition to these commands that are a part of NSH, external programs can also be executed as NSH commands. These external programs are called "Built-In" Applications for historic reasons. That terminology is somewhat confusing because the actual NSH commands as described above are truly "built-into" NSH whereas these applications are really external to NuttX.

These applications are built-into NSH in the sense that they can be executed by simply typing the name of the application at the NSH prompt. Built-in application support is enabled with these configuration option:

• CONFIG_BUILTIN: Enable NuttX support for builtin applications.
• CONFIG_NSH_BUILTIN_APPS: Enable NSH support for builtin applications.

When these configuration options are set, you will also be able to see the built-in applications if you enter "nsh> help". They will appear at the bottom of the list of NSH commands under:

Builtin Apps:

Note that no detailed help information beyond the name of the built-in application is provided.

5.3.1 Built-In Applications

Overview. The underlying logic that supports the NSH built-in applications is called "Built-In Applications". The builtin application logic can be found at apps/builtin. This logic simply does the following:

1. It supports registration mechanism so that builtin applications can dynamically register themselves at build time, and

2. Utility functions to look up, list, and execute the builtin applications.

Built-In Application Utility Functions. The utility functions exported by the builtin application logic are prototyped in nuttx/include/nuttx/binfmt/builtin.h and apps/include/builtin.h. These utility functions include:

• int builtin_isavail(FAR const char *appname); Checks for availability of application registered as appname during build time.

• const char *builtin_getname(int index); Returns a pointer to a name of built-in application pointed by the index. This is the utility function that is used by NSH in order to list the available built-in applications when "nsh> help" is entered.

• int exec_builtin(FAR const char *appname, FAR const char **argv); Executes built-in builtin application registered during compile time. This is the utility function used by NSH to execute the built-in application.

Autogenerated Header Files. Application entry points with their requirements are gathered together in two files when NuttX is first built:

1. apps/builtin/builtin_proto.h: Prototypes of application task entry points.

2. apps/builtin/builtin_list.h: Application specific information and start-up requirements

Registration of Built-In Applications. The NuttX build occurs in several phases as different build targets are executed: (1) context when the configuration is established, (2) depend when target dependencies are generated, and (3) default (all) when the normal compilation and link operations are performed. Built-in application information is collected during the make context build phase.

An example application that can be "built-in" is be found in the apps/examples/hello directory. Let's walk through this specific cause to illustrate the general way that built-in applications are created and how they register themselves so that they can be used from NSH.

apps/examples/hello. The main routine for apps/examples/hello can be found in apps/examples/hello/main.c. The main routine is:

int hello_main(int argc, char *argv[])
{
  printf("Hello, World!!\n");
  return 0;
}

This is the built in function that will be registered during the context build phase of the NuttX build. That registration is performed by logic in apps/examples/hello/Makefile. But the build system gets to that logic through a rather tortuous path:

1. The top-level context make target is in nuttx/Makefile. All build targets depend upon the context build target. For the apps/ directory, this build target will execute the context target in the apps/Makefile.

2. The apps/Makefile will, in turn, execute the context targets in all of the configured sub-directories. In our case will include the Makefile in apps/examples.

3. And finally, the apps/examples/Makefile will execute the context target in all configured examplesub-directories, getting us finally to apps/examples/Makefile which is covered below.

NOTE: Since this context build phase can only be executed one time, any subsequent configuration changes that you make will, then, not be reflected in the build sequence. That is a common area of confusion. Before you can instantiate the new configuration, you have to first get rid of the old configuration. The most drastic way to this is:

make distclean

But then you will have to re-configuration NuttX from scratch. But if you only want to re-build the configuration in the apps/ sub-directory, then there is a less labor-intensive way to do that. The following NuttX make command will remove the configuration only from the apps/ directory and will let you continue without re-configuring everything:

make apps_distclean

Logic for the context target in apps/examples/hello/Makefile registers the hello_main() application in the builtin's builtin_proto.hand builtin_list.h files. That logic that does that in apps/examples/hello/Makefile is abstracted below:

1. First, the Makefile includes apps/Make.defs:

   include $(APPDIR)/Make.defs
   

   This defines a macro called REGISTER that adds data to the builtin header files:

   define REGISTER
       @echo "Register: $1"
       @echo "{ \"$1\", $2, $3, $4 }," >> "$(APPDIR)/builtin/builtin_list.h"
       @echo "EXTERN int $4(int argc, char *argv[]);" >> "$(APPDIR)/builtin/builtin_proto.h"
   endef
   

   When this macro runs, you will see the output in the build "Register: hello", that is a sure sign that the registration was successful.

2. The make file then defines the application name (hello), the task priority (default), and the stack size that will be allocated in the task runs (2K).

   APPNAME         = hello
   PRIORITY        = SCHED_PRIORITY_DEFAULT
   STACKSIZE       = 2048
   

3. And finally, the Makefile invokes the REGISTER macro to added the hello_main() builtin application. Then, when the system build completes, the hello command can be executed from the NSH command line. When the hello command is executed, it will start the task with entry point hello_main() with the default priority and with a stack size of 2K.

   context:
     $(call REGISTER,$(APPNAME),$(PRIORITY),$(STACKSIZE),$(APPNAME)_main)
   

Other Uses of Built-In Application. The primary purpose of builtin applications is to support command line execution of applications from NSH. However, there is one other use of builtin applications that should be mentioned.

1. binfs. binfs is a tiny file system located at apps/builtin/binfs.c. This provides an alternative what of visualizing installed builtin applications. Without binfs, you can see the installed builtin applications using the NSH help command. binfs will create a tiny pseudo-file system mounted at /bin. Using binfs, you can see the available builtin applications by listing the contents of /bin directory. This gives some superficial Unix-like compatibility, but does not really add any new functionality.

5.3.2 Synchronous Built-In Applications

By default, built-in commands started from the NSH command line will run asynchronously with NSH. If you want to force NSH to execute commands then wait for the command to execute, you can enable that feature by adding the following to the NuttX configuration file:

CONFIG_SCHED_WAITPID=y

This configuration option enables support for the standard waitpid() RTOS interface. When that interface is enabled, NSH will use it to wait, sleeping until the built-in application executes to completion.

Of course, even with CONFIG_SCHED_WAITPID=y defined, specific applications can still be forced to run asynchronously by adding the ampersand (&) after the NSH command.

Ways to Customize NSH Initialization. There are three ways to customize the NSH start-up behavior. Here they are presented in order of increasing difficulty:

1. You can extend the initialization logic in configs/stm3240g-eval/src/stm32_appinit.c. The logic there is called each time that NSH is started and is good place in particular for any device-related initialization.

2. You replace the sample code at apps/examples/nsh/nsh_main.c with whatever start-up logic that you want. NSH is a library at apps/nshlib. apps.examples/nsh is just a tiny, example start-up function (CONFIG_USER_ENTRYPOINT()) that that runs immediately and illustrates how to start NSH If you want something else to run immediately then you can write your write your own custom CONFIG_USER_ENTRYPOINT() function and then start other tasks from your custom CONFIG_USER_ENTRYPOINT().

3. NSH also supports a start-up script that executed when NSH first runs. This mechanism has the advantage that the start-up script can contain any NSH commands and so can do a lot of work with very little coding. The disadvantage is that is is considerably more complex to create the start-up script. It is sufficiently complex that is deserves its own paragraph

5.4.1 NuttShell Start up Scripts

First of all you should look at NSH Start-Up Script paragraph. Most everything you need to know can be found there. That information will be repeated and extended here for completeness.

NSH Start-Up Script. NSH supports options to provide a start up script for NSH. The start-up script contains any command support by NSH (i.e., that you see when you enter 'nsh> help'). In general this capability is enabled with CONFIG_NSH_ROMFSETC=y, but has several other related configuration options as described with the NSH-specific configuration settings paragraph. This capability also depends on:

• CONFIG_DISABLE_MOUNTPOINT=n. If mount point support is disabled, then you cannot mount any file systems.

• CONFIG_NFILE_DESCRIPTORS > 4. Of course you have to have file descriptions to use any thing in the file system.

• CONFIG_FS_ROMFS enabled. This option enables ROMFS file system support.

Default Start-Up Behavior. The implementation that is provided is intended to provide great flexibility for the use of Start-Up files. This paragraph will discuss the general behavior when all of the configuration options are set to the default values.

In this default case, enabling CONFIG_NSH_ROMFSETC will cause NSH to behave as follows at NSH start-up time:

• NSH will create a read-only RAM disk (a ROM disk), containing a tiny ROMFS file system containing the following:

  `--init.d/
      `-- rcS
  

  Where rcS is the NSH start-up script.

• NSH will then mount the ROMFS file system at /etc, resulting in:

  |--dev/
  |   `-- ram0
  `--etc/
      `--init.d/
          `-- rcS

• By default, the contents of rcS script are:

  # Create a RAMDISK and mount it at /tmp
  
  mkrd -m 1 -s 512 1024
  mkfatfs /dev/ram1
  mount -t vfat /dev/ram1 /tmp
  

• NSH will execute the script at /etc/init.d/rcS at start-up (before the first NSH prompt). After execution of the script, the root FS will look like:

  |--dev/
  |   |-- ram0
  |   `-- ram1
  |--etc/
  |   `--init.d/
  |       `-- rcS
  `--tmp/
  

Example Configurations. Here are some configurations that have CONFIG_NSH_ROMFSETC=y in the NuttX configuration file. They might provide useful examples:

configs/hymini-stm32v/nsh2
configs/ntosd-dm320/nsh
configs/sim/nsh
configs/sim/nsh2
configs/sim/nx
configs/sim/nx11
configs/sim/touchscreen


rcS.template. The default rcS.template, apps/nshlib/rcS.template, generates the standard, default apps/nshlib/nsh_romfsimg.h file.

If CONFIG_NSH_ARCHROMFS is defined in the NuttX configuration file, then a custom, board-specific nsh_romfsimg.h file residing in configs/<board>/includewill be used. NOTE when the OS is configured, include/arch/board will be linked to configs/<board>/include.

All of the startup-behavior is contained in rcS.template. The role of mkromfsimg.sh script is to (1) apply the specific configuration settings to rcS.template to create the final rcS, and (2) to generate the header file nsh_romfsimg.h containing the ROMFS file system image. To do this, mkromfsimg.sh uses two tools that must be installed in your system:

1. The genromfs tool that is used to generate the ROMFS file system image.

2. The xxd tool that is used to create the C header file.

NuttShell sessions can be protected by requiring that the user supply username and password credentials at the beginning of the session. Logins can be enabled for standard USB or serial consoles with:

CONFIG_NSH_CONSOLE_LOGIN=y

Logins for Telnet sessions can be enabled separately with:

CONFIG_NSH_TELNET_LOGIN=y

Logins can be enabled for either or both session types. On a successful login, the user will have access to the NSH session:

login: admin
password:
User Logged-in!

NuttShell (NSH)
nsh>

After each failed login attempt, a delay can be set up. The purpose of this delay is to discourage attempts to crack the password by brute force. That delay is configured with

CONFIG_NSH_LOGIN_FAILDELAY=0

This setting provides the login failure delay in units of milliseconds. The system will pause this amount of time after each failed login attempt. After a certain number of failed login attempts, the session will be closed. That number is controlled by:

CONFIG_NSH_LOGIN_FAILCOUNT=3

There are three ways that NSH can be configured to verify user credentials at login time:

1. The simplest implementation simply uses fixed login credentials and is selected with:

   CONFIG_NSH_LOGIN_FIXED=y
   

   The fixed login credentials are selected via:

   CONFIG_NSH_LOGIN_USERNAME=admin
   CONFIG_NSH_LOGIN_PASSWORD="Administrator"
   

   This is not very flexible since there can be only one user and the password is fixed in the FLASH image. This option is also not very secure because a malicious user could get the password by just looking at the .text stings in the flash image.

2. NSH can also be configured to defer the entire user credential verification to platform-specific logic with this setting:

   CONFIG_NSH_LOGIN_PLATFORM=y
   

   In this case, NSH will call a platform-specific function to perform the verification of user credentials. The platform-specific logic must provide a function with the following prototype:

   int platform_user_verify(FAR const char *username, FAR const char *password);
   

   which is prototyped an described in apps/include/nsh.h and which may be included like:

   #include <apps/nsh.h>
   

   An appropriate place to implement this function might be in the directory apps/platform/<board>.

3. A final option is to use a password file contained encrypted password information. This final option is selected with the following and described in more detail in the following paragraph.

   CONFIG_NSH_LOGIN_PASSWD=y
   

NuttX can also be configured to support a password file, by default at /etc/passwd. This option enables support for a password file:

CONFIG_NSH_LOGIN_PASSWD=y

This options requires that you have selected CONFIG_FSUTILS_PASSWD=y to enable the access methods of apps/fsutils/passwd:

CONFIG_FSUTILS_PASSWD=y

And this determines the location of the password file in a mounted volume:

CONFIG_FSUTILS_PASSWD_PATH="/etc/passwd"

/etc/passwd is a standard location, but you will need to locate the password where ever you have a mounted volume.

The password file can be a fixed list of users in a ROMFS file system or a modifiable list maintained in a file in some writable file system. If the password file lies in a read-only file system like ROMFS, then you should also indicate that the password file is read-only.

CONFIG_FSUTILS_PASSWD_READONLY=y

If the password file is writable, then additional NSH commands will be enabled to modify the password file: useradd, userdel, and passwd. If you do not wish you have these commands available, then they should be specifically disabled.

The password file logic requires a few additional settings:

1. The size of dynamically allocated and freed buffer that is used for file access:

   CONFIG_FSUTILS_PASSWD_IOBUFFER_SIZE=512
   

2. And the 128-bit encryption key. The password file currently uses the Tiny Encryption Algorithm (TEA), but could be extended to use something more powerful.

   CONFIG_FSUTILS_PASSWD_KEY1=0x12345678
   CONFIG_FSUTILS_PASSWD_KEY2=0x9abcdef0
   CONFIG_FSUTILS_PASSWD_KEY3=0x12345678
   CONFIG_FSUTILS_PASSWD_KEY4=0x9abcdef0
   

Password can only be decrypted with access to this key. Note that this key could potentially be fished out of your FLASH image, but without any symbolic information, that would be a difficult job since the TEA KEY is binary data and not distinguishable from other binary data in the FLASH image.

If the password file is enabled (CONFIG_NSH_LOGIN_PASSWD=y), then the fixed user credentials will not be used for the NSH session login. Instead, the password file will be consulted to verify the user credentials.

What we want to accomplish is a ROMFS file system, mounted at /etc and containing the password file, passwd like:

NuttShell (NSH)
nsh> ls -Rl /etc
/etc:
 dr-xr-xr-x       0 .
 dr-xr-xr-x       0 init.d/
 -r--r--r--      39 passwd
/etc/init.d:
 dr-xr-xr-x       0 ..
 -r--r--r--     110 rcS
nsh>

Where /etc/init.d/rcS is the start-up script; /etc/passwd is a the password file. Note that here we assume that you are already using a start-up script. We can then piggyback the passwd file into the /etc file system already mounted for the NSH start up file as described above above.

I use the sim/nsh configuration to create a new password file, but other configurations could also be used. That configuration already supports a ROMFS file system, passwords, and login prompts. First, I make these changes to that configuration.

1. Disable logins

   - CONFIG_NSH_CONSOLE_LOGIN=y
   + # CONFIG_NSH_CONSOLE_LOGIN is not set
     # CONFIG_NSH_TELNET_LOGIN is not set
   

2. Move the password file to a write-able file system:

   - CONFIG_FSUTILS_PASSWD_PATH="/etc/passwd"
   + CONFIG_FSUTILS_PASSWD_PATH="/tmp/passwd"
   

3. Make the password file modifiable

   - CONFIG_FSUTILS_PASSWD_READONLY=y
   # CONFIG_FSUTILS_PASSWD_READONLY is not set
   

Now rebuild the simulation. No login should be required to enter the shell and you should find the useradd, userdel, and passwd commands available in the help summary, provided that they are enabled. Make certain that the useradd command is not disabled:

# CONFIG_NSH_DISABLE_USERADD is not set

Use the NSH useradd command to add new uses with new user passwords like:

nsh> useradd <username> <password>

Do this as many times as you would like. Each time that you do this a new entry with an encrypted password will be added to the passwd file at /tmp/passwd. You can see the content of the password file like:

nsh> cat /tmp/passwd

When you are finished, you can simply copy the /tmp/passwd content from the cat command and paste it into an editor. Make sure to remove any carriage returns that may have ended up on the file if you are using Windows.

Then create/re-create the nsh_romfsimg.h file as described below.

1. The content on the nsh_romfsimg.h header file is generated from a template directory structure. Create the directory structure:

   mkdir etc
   mkdir etc/init.d
   

   And copy your existing startup script into etc/init.c as rcS.

2. Save your new password file in the etc/ directory as passwd.

3. Create the new ROMFS image.

   genromfs -f romfs_img -d etc -V MyVolName
   

4. Convert the ROMFS image to a C header file

   xxd -i romfs_img >nsh_romfsimg.h
   

5. Edit nsh_romfsimg.h: Mark both data definitions as const so that the data will be stored in FLASH.

6. Edit nsh_romfsimg.h, mark both data definitions as const so that that will be stored in FLASH.

There is a good example of how to do this in the NSH simulation configuration at configs/sim/nsh. The ROMFS support files are provided at configs/sim/include and the README.txt file at the location provides detailed information about creating and modifying the ROMFS file system.