Learning Objectives

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After completing this section, you will be able to:

• Understand the C interpreter
• Understand the command interpreter
• Use common and useful kernel shell functions

The VxWorks kernel shell supports two modes: the C interpreter and the command interpreter, each designed for specific tasks in development, debugging, and system management.

Switching Between Shell Modes

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To switch between modes, type the interpreter name into the shell:

-> cmd
[vxWorks *]# C
->

You can also prefix a single command with an interpreter to execute it immediately:

-> cmd
[vxWorks *]# C x=42
New Symbol “x” added to kernel symbol table.
value = 42 = 0x2a = '*'
[vxWorks *]# C
->

The C Interpreter in VxWorks

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Features of the C Interpreter

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1. Ideal for prototyping and debugging in kernel space

2. Allows manipulation of global variables:

   • Examine values
   • Change values
   • Create new variables

3. Invokes almost any function in memory:

   • Passes up to 10 arguments to functions, padding with zeros if needed
   • Prints function call results and other evaluated expressions

Using the C Interpreter

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Type C (uppercase) to start the interpreter. Its syntax closely resembles standard C:

Working with Variables

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1. Assigning a value to an undefined symbol creates a new variable
2. Interpreter searches for symbols in the symbol table
3. 32-bit vs 64-bit interpreters interpret integer sizes differently
4. Use casts to interpret non-integer types (temporary per access)
5. Supported types include: long long, unsigned types, scientific notation

C Interpreter Notes

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• Parentheses in function calls can sometimes be omitted:

-> func &mac, 27

• Symbolic macros are not supported:

-> sem1 = semMCreate(SEM_Q_PRIORITY)   # ❌
-> sem1 = semMCreate(0x1)             # ✅

The Command Interpreter in VxWorks

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Features of the Command Interpreter

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Switch to the command interpreter using:

-> cmd

1. Monitor and debug RTPs

2. UNIX-style commands:

   • File: pwd, cat, cd
   • Task: task spawn, task info, task delete

3. Supports command aliasing:

[vxWorks *]# alias foo "task info"

4. Symbol evaluation:

[vxWorks *]# echo Address = &test Value = $test

RTP Commands in Command Interpreter

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• Launch help: -> help rtp
• Launch an RTP: -> rtp exec fn
• Show all RTPs: -> rtp
• Attach to one RTP: -> rtp attach 0xN
• Show tasks in attached RTP: -> rtp task

Command Interpreter Features

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Supports shell control characters:

• Pipe:

[vxWorks *]# cat file.txt | more

• Backquote evaluation:

[vxWorks *]# bp 'expr &printf + 0x4'

• Input/output redirection:

[vxWorks *]# cat file > file2
[vxWorks *]# /foo/bar/rtp.vxe < file2 >> file2

Useful Shell Functions

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Debugging Commands

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Dynamic printf commands (dprintf) help locate race conditions and debug without recompiling:

1. Enable INCLUDE_DEBUG for dprintf() and hdprintf() in C interpreter
2. Enable INCLUDE_DEBUG_SHELL_CMD for command interpreter dprintf
3. Allows runtime printf insertion in kernel modules or RTPs

System Information Commands

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Show Functions

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Provide detailed target system info (C interpreter only, requires associated VIP component):

• taskShow() – Configure INCLUDE_TASK_SHOW
• memShow() – Configure INCLUDE_MEM_SHOW