Arguments

fileName  string, name of the file to be opened, can contain a fully specified path; if no path is specified, the standard folder search sequence is used as with (findfile); 

openMode  string, specifies whether opening for read/write is requested :
"r"  opening for read operations
"w"  opening for write operations, file content is automatically cleared, file is created if not existing yet
"a"  opening for append, file content is not cleared, file is created if not existing yet

BricsCAD supports to open a file in "binary" mode :
"rb"
"wb"
"ab"
modes can be used to specify the "binary" mode : characters are not translated, but written "as is"

BricsCAD Lisp supports extended openMode settings, please see read + write text files

encoding  : (optional) string, specifies UTF-8 with or without BOM; allowed "utf8" and "utf8-bom";
if using UTF-8 format, it is *strongly* suggested to use "UTF-8 with BOM" (UTF-8 without BOM can not be distinguished from normal ANSII !)

Return

"file descriptor" (value of type FILE) if opening was successful, NIL if opening failed

Example

(open "on_doc_load.lsp" "r")  #<FILE : nnnnnn>
(open "ThisFileDoesNotExist.txt" "r")  NIL
(open "ThisFileDoesNotExist.txt" "w")  #<FILE : nnnnnn>
(open "ThisFileDoesNotExist.txt" "r")  #<FILE : nnnnnn>

Remarks

1. the new encoding option, as introduced by AutoCAD 2021, is supported in BricsCAD V21 and higher;

2. see (findfile) function, and SRCHPATH / ACADPREFIX settings;
for some BricsCAD-specific and backward-compatible extension, please see detailed informations for opening non-ASCII/ANSI files in Extended AutoLISP Functions

3. BricsCAD Lisp supports extended openMode settings, please see read + write text files