open (AutoLISP)

Opens a file for access by the AutoLISP I/O functions

Supported Platforms: Windows and Mac OS

Signature

(open filename mode)

filename

Type: String

Name and extension of the file to be opened. If you do not specify the full path name of the file, open assumes you are referring to the AutoCAD default drawing directory.

mode

Type: String

Indicates whether the file is open for reading, writing, or appending. Specify a string containing one of the following letters:

r Open for reading.

w Open for writing. If filename does not exist, a new file is created and opened. If filename already exists, its existing data is overwritten. Data passed to an open file is not actually written until the file is closed with the close function.

a Open for appending. If filename does not exist, a new file is created and opened. If filename already exists, it is opened and the pointer is positioned at the end of the existing data, so new data you write to the file is appended to the existing data.

The mode argument can be uppercase or lowercase. Note that in releases prior to AutoCAD 2000, mode had to be specified in lowercase.

Return Values

Type: File or nil

If successful, open returns a file descriptor that can be used by the other I/O functions. If mode "r" is specified and filename does not exist, open returns nil.

Examples

Windows

Open an existing file:

(setq a (open "c:/datafiles/filelist.txt" "r"))
#<file "c:/datafiles/filelist.txt">

The following examples issue open against files that do not exist:

(setq f (open "c:\\my documents\\new.tst" "w"))
#<file "c:\\my documents\\new.tst">

(setq f (open "nosuch.fil" "r"))
nil

(setq f (open "logfile" "a"))
#<file "logfile">

Mac OS