Learning Objectives

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After completing this section, you will be able to:

• Use the VI editor for command-line editing
• Enable and use Emacs mode
• Describe and implement the object-module loader

The VxWorks kernel shell leverages command-line editors to improve development efficiency. It also provides an object-module loader to dynamically load and unload code at runtime.

Command Line Editing

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The kernel shell supports VI as the primary editor and Emacs as a secondary editor. Commands entered in the shell are stored in a history buffer, with a default maximum length of 20 commands. The shell also supports command-line completion.

Navigating in VI

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To work in the VI editor, press ESC to enter line-editing mode. Key commands include:

• k - Move backward through history buffer
• j - Move forward through history buffer
• h - Move cursor left
• l - Move cursor right
• a - Append after cursor
• A - Append at end of line
• i - Insert before cursor
• I - Insert at beginning of line
• rc - Replace current character with character c
• x - Delete current character
• dd - Delete entire line
• nG - Go to history line or search for string

Command-Line Completion

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The shell supports command and file autocompletion:

• CTRL+D - List symbols
• CTRL+D, TAB - Autocomplete symbols or file names

Enabling Emacs Mode

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Emacs can be enabled with the following command:

shConfig "LINE_EDIT_MODE=emacs"

Note: Emacs provides more features than VI but has higher overhead, which is why VI is the default editor.

Command History Limit

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You can modify the history buffer size using the h() function. For example, h 500 increases the buffer size to 500 commands.

Object-Module Loader

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The object-module loader allows the kernel to dynamically load and unload code at runtime. This enables iterative development without rebuilding the VIP or rebooting the target for every code change.

After configuration, two primary functions become available:

• ld() – Load object modules into the C interpreter
• unld() – Unload object modules

The object-module loader seamlessly integrates new code with the existing VxWorks image, allowing for dynamic expansion. It also manages memory allocation, either dynamically for downloaded modules or with pre-specified addresses for fine-grained control.