M118 - Send Message

DMC File Mode: Not Supported

Streaming Mode: Supported

Description

M118 sends a string message through the command completed callback via a result payload. Everything after M118 is treated as the message text.

This command is useful for sending status updates, debug information, or progress messages from a G-code program back to the host application. The original casing and special characters in the message are preserved.

Result Payload: M118 returns a result with type GCODE_RESULT_MESSAGE. Use the result accessor functions to read the message string from inside the command completed callback.

Syntax

M118 <message text>

Parameters

Parameter	Description
<message text>	Everything after `M118` is the message. Special characters, spaces, and mixed casing are all preserved. If omitted, an empty message is sent.

Result Data

Field	Value
Result Type	`GCODE_RESULT_MESSAGE` (2)
Key	`"message"`
Value Type	`string` — the message text
Count	1

Examples

G-Code Usage

; Send a status message

M118 Starting drill cycle

G81 X10 Y10 Z-5 R1 F100

; Send completion message

M118 Drill cycle complete!

Reading the Message in the Callback (C API)

void on_completed(int index, int total, const char* cmd,
                  GCodeResultHandle result, void* data) {
    if (gcode_result_get_type(result) == GCODE_RESULT_MESSAGE) {
        const char* message = NULL;
        if (gcode_result_get_string(result, "message", &message) == GCODE_OK) {
            printf("G-code message: %s\n", message);
        }
    }
}

Expected output for M118 Starting drill cycle:

G-code message: Starting drill cycle

Notes

The message preserves its original casing — M118 Hello World delivers "Hello World", not "HELLO WORLD".
Special characters (!, @, #, %, etc.) are allowed and preserved in the message.
If no message text is provided (just M118), an empty string is delivered.
The GCodeResultHandle is only valid during the callback invocation. Copy the message string before the callback returns.