en
italiano
čeština
Deutsch
français
hrvatski
magyar
polski
српски
русский
中文
中文
한국어
español(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
- In append mode, new data is added to the end of the existing file.
- LISP only reads ASCII files (no binary files) using sequential access (no random access).
- To separate subdirectory names, you use either two backslashes ( \\ ) or a single forward slash ( / ).