18 File Handling

The operating system stores data permanently in named files, so most of the text you edit with Emacs comes from a file and is ultimately stored in a file.

To edit a file, you must tell Emacs to read the file and prepare a buffer containing a copy of the file’s text. This is called visiting the file. Editing commands apply directly to text in the buffer; that is, to the copy inside Emacs. Your changes appear in the file itself only when you save the buffer back into the file.

In addition to visiting and saving files, Emacs can delete, copy, rename, and append to files, keep multiple versions of them, and operate on file directories.

• File Names		How to type and edit file-name arguments.
• Visiting		Visiting a file prepares Emacs to edit the file.
• Saving		Saving makes your changes permanent.
• Reverting		Reverting cancels all the changes not saved.
• Auto Revert		Keeping buffers automatically up-to-date.
• Auto Save		Auto Save periodically protects against loss of data.
• File Aliases		Handling multiple names for one file.
• Directories		Creating, deleting, and listing file directories.
• Comparing Files		Finding where two files differ.
• Diff Mode		Mode for editing file differences.
• Copying and Naming		Copying, naming and renaming files.
• Misc File Ops		Other things you can do on files.
• Compressed Files		Accessing compressed files.
• File Archives		Operating on tar, zip, jar etc. archive files.
• Remote Files		Accessing files on other machines.
• Quoted File Names		Quoting special characters in file names.
• File Name Cache		Completion against a list of files you often use.
• File Conveniences		Convenience features for finding files.
• Image Mode		Viewing image files.
• Filesets		Handling sets of files.