&opt(4)

NAME

&opt - MicroEmacs optional feature test

SYNOPSIS

&opt str

DESCRIPTION

This function can be used to test the availability of optional features in the current session of MicroEmacs. Some features, like spelling checker support, are a compilation option, other options like mouse support may also be unavailable on some platforms. The &opt function can be used by macros to check that required base functionality is available.

The function returns 1 in the given feature "str" is supported, otherwise it returns 0 if the feature is unknown or not supported in the running version.

Optional components of MicroEmacs are enabled/disabled at compile time, most options are configured by MEOPT_<NAME> #define's within the source file emain.h. Following is a complete list of options, giving the opt string and #define label:

abb - MEOPT_ABBREV


Abbreviation functionality (see expand-abbrev(2)).

cal - MEOPT_CALLBACK


Callback and idle event handling (see create-callback(2)).

cli - MEOPT_CLIENTSERVER


Client/server support (see Client-Server).

col - MEOPT_COLOR


All color support (making hilighting redundent etc, see add-color(2)).

cry - MEOPT_CRYPT


File encryption (see crypt(2m) mode).

deb - MEOPT_DEBUGM


Macro debugging (see $debug(5)).

dir - MEOPT_DIRLIST


Generate directory listing when loading a directory (see find-file(2) and file-browser(3)).

ext - MEOPT_EXTENDED


Miscellaneous more advanced commands and features such as append-buffer(2), generate-hash(2) and screen-poke(2).

fen - MEOPT_FENCE


Fence matching (see user-setup(3) and fence(2m)).

fra - MEOPT_FRAME


Multiple frames (Internal or external, see opt "mwf" and command create-frame(2)).

has - MEOPT_CMDHASH


Use a hash table for rapid command name lookup, not to be confused with generate-hash(2) which is an extended command.

hil - MEOPT_HILIGHT


Hilight and user definable indentation rules (see hilight(2) and indent(2)).

hsp - MEOPT_HSPLIT


Horizontal window splitting (see split-window-horizontally(2)).

ipi - MEOPT_IPIPES


Interactive pipes (see ipipe-shell-command(2)).

ise - MEOPT_ISEARCH


Incremental search (see isearch-forward(2)).

lbi - MEOPT_LOCALBIND


Buffer, message-line and OSD local binding overrides (see buffer-bind-key(2)).

mag - MEOPT_MAGIC


Regular expression search engine (see magic(2m) mode).

mjm - MEOPT_MAJORMODE


File major-mode auto-detection and configuration (see major-mode(2)).

mou - MEOPT_MOUSE


Mouse support (see $mouse(5)).

mwf - MEOPT_MWFRAME


Multiple window frame support (see opt "fra").

nar - MEOPT_NARROW


Buffer narrowing (see narrow-buffer(2)).

nex - MEOPT_FILENEXT


Location list stepping (see get-next-line(2)).

osd - MEOPT_OSD


On Screen Display GUI support (see osd(2)).

pri - MEOPT_PRINT


Printing support (see print-buffer(2)).

rcs - MEOPT_RCS


File Revision Control Support (see $rcs-co-com(5)).

reg - MEOPT_REGISTRY


Internal registry and history support (see read-registry(2)).

scr - MEOPT_SCROLL


Window scroll-bar support.

soc - MEOPT_SOCKET


FTP and HTTP URL support via sockets (see find-file(2)).

spa - MEOPT_SPAWN


External process launching (see shell-command(2)).

spe - MEOPT_SPELL


Spelling checker support (see spell(2)).

ssl - MEOPT_OPENSSL


FTPE, FTPS and HTTPS Secure URL support via OpenSSL (see find-file(2) and %http-flags(5)).

tag - MEOPT_TAGS


Tags support (see find-tag(2)).

tim - MEOPT_TIMSTMP


File timestamping on save (see time(2m) mode).

typ - MEOPT_TYPEAH


Input detect or 'type-ahead' for background processing support.

und - MEOPT_UNDO


Undo support (see undo(2)).

wor - MEOPT_WORDPRO


Word-processor style commands like fill-paragraph(2) (see forward-paragraph(2)).

EXAMPLE

The following example checks for URL support and if not available it pops up an error:

!if &not &opt "soc" 
    osd-dialog "Opt Test" "Error: No URL support!" "  &OK  " 
!endif 

NOTES

The output of command about(2) includes a full list of all available optional features.

For secure URL (https) support to work the binary must be built with MEOPT_OPENSSL and the appropriate libssl and libcrypto runtime libraries must be available; &opt does not confirm the availability of the libraries.

SEE ALSO

about(2), Building MicroEmacs.

Ref: &opt(4) File: m4fil035.4 Date: 2026/01/17

(c) Copyright JASSPA 2026