Elisp programming 4: File Operations

Determine whether a file exists

 
(File-exists-P "~ /Test. El ")
 

See its help documentation:

 
File-exists-P is a built-in function in 'C source Code '. (file-exists-P filename) return T if file filename exists (whether or not you can read it .) see also 'file-readable-p' and 'file-bubutes '. this Returns nil for a symlink to a nonexistent file. use 'file-symlink-p' to test for such links.
 

If yes, t is returned.

Check whether a file exists and is readable

 
(File-readable-P "~ /Test. El ")
 

Check file attributes

 
(File-attributes "~ /Test. El "'string)
 

Or

(File-attributes "~ /Test. El "'integer)
 

The list in the above two rows displays the object attributes in the form of string or integer list, ranging from 0 to 11, with a total of 12 attributes.

You can obtain whether a file is a directory.

Example of a directory operation

Assume that the sub-directory names in a directory are all numbers, and find the directory name with the largest number.

 
(Setq file-name-List (directory-Files "/opt/share/upland_release" nil "[0-9] +" 'nosort )) (string-to-number (CAR file-name-list ))
 

For other file functions, see

The file-related chapter for the http://www.gnu.org/software/emacs/manual/html_mono/elisp.html.