(open filename mode)


Open that file.


This function makes a file's filename accessible for input and output functions. The filename argument represents the path and filename of the file to open.

The open function returns a file descriptor (an 8-digit hexadecimal number) for the opened file, which should be stored as a variable using the setq function. Once you have the file descriptor, you must refer to the file using the file descriptor-not the filename!

The mode argument has three options, which must be in lowercase:

Mode Meaning
"r" Open the file as read-only; returns nil if the file does not exist.
"w" Open the file for writing; overwrites existing data; creates a new file if non-existent.
"a" Open the file for writing; append to existing data; creates a new file if non-existent.

Examples

Code Returns
(setq n (open "existing.txt" "w")) <File: #2190dec2>
(setq n (open "noexist.lsp" "r")) nil
(setq n (open "\\sample\\exiting.txt" "a") <File: #2190c2c3>

NOTES