on exec_errors

Synopsis

/on [<noise>]exec_errors "<pattern>" [(<argument list>)] { <commands> }

Description

Triggered for a line read from the standard error of a process started with exec, unless that process has a nonempty -error callback. This identifies the stream, not whether the program has failed: programs can write informational text to stderr too. Standard output uses on exec; process termination uses on exec_exit.

The current reader is line-buffered, so incomplete output without a newline waits for more data rather than triggering this event immediately. The partial-line branch is disabled. Use the standard on matching and noise controls; there are no event-specific options.

Parameters

Parameter	Meaning
`$0`	Process logical name, if assigned; otherwise its numeric exec refnum.
`$1-`	A line of the process's stderr output.

The numeric refnum has no leading % and is not the operating-system process ID. Trailing carriage returns and newlines are stripped, and the text undergoes incoming character-set conversion configured for the process. The pattern matches the identifier and line together.

Default behavior and callbacks

If the hook permits default handling, EPIC displays the line without an error label, unless the process's redirect setting is active. A suppressing hook, such as a serial-zero ^exec_errors hook, prevents that default line and can supply replacement output.

A nonempty exec -error { ... } callback runs instead of this hook and its default display. It receives the line without the process identifier prepended. The stdout -line callback does not replace this stderr hook. Output runs in the process's stored server context, using its output window when assigned, at the other message level.

The -out, -msg, and -notice options set redirect metadata and suppress default local display without disabling the hook. In the current output reader, that metadata does not itself forward stderr lines to IRC: there is no redirect send step. Scripts must explicitly send lines if wanted.

Suppressing display does not stop the process, stop reading its output, or prevent the line from counting toward output limits. Set shell_limit and the process's -limit value can stop further output handling; stdout and stderr contribute to the same received-line count.

Example

Distinguish stderr from other window output:

on ^exec_errors "*" {
    echo [$0 ERR] $1-;
};

This replaces ordinary local display for processes without a nonempty -error callback.

Source references

source/exec.c: do_exec routes stderr to exec_errors and applies output limits; handle_filedesc selects stderrc, strips line endings, converts encoding, invokes callbacks or hooks, and controls display; set_context_for_process selects output context; option handling records -error and redirect metadata.
source/hook.c: event registration and do_hook implement standard matching and suppression.