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This chapter describes the functions that deal with the text in a buffer. Most examine, insert, or delete text in the current buffer, often operating at point or on text adjacent to point. Many are interactive. All the functions that change the text provide for undoing the changes (see Undo).

Many text-related functions operate on a region of text defined by two buffer positions passed in arguments named start and end. These arguments should be either markers (see Markers) or numeric character positions (see Positions). The order of these arguments does not matter; it is all right for start to be the end of the region and end the beginning. For example, (delete-region 1 10) and (delete-region 10 1) are equivalent. An args-out-of-range error is signaled if either start or end is outside the accessible portion of the buffer. In an interactive call, point and the mark are used for these arguments.

Throughout this chapter, “text" refers to the characters in the buffer, together with their properties (when relevant). Keep in mind that point is always between two characters, and the cursor appears on the character after point.

Near Point  Examining text in the vicinity of point.
Buffer Contents  Examining text in a general fashion.
Comparing Text  Comparing substrings of buffers.
Insertion  Adding new text to a buffer.
Commands for Insertion  User-level commands to insert text.
Deletion  Removing text from a buffer.
User-Level Deletion  User-level commands to delete text.
The Kill Ring  Where removed text sometimes is saved for later use.
Undo  Undoing changes to the text of a buffer.
Maintaining Undo  How to enable and disable undo information. How to control how much information is kept.
Filling  Functions for explicit filling.
Margins  How to specify margins for filling commands.
Adaptive Fill  Adaptive Fill mode chooses a fill prefix from context.
Auto Filling  How auto-fill mode is implemented to break lines.
Sorting  Functions for sorting parts of the buffer.
Columns  Computing horizontal positions, and using them.
Indentation  Functions to insert or adjust indentation.
Case Changes  Case conversion of parts of the buffer.
Text Properties  Assigning Lisp property lists to text characters.
Substitution  Replacing a given character wherever it appears.
Registers  How registers are implemented. Accessing the text or position stored in a register.
Transposition  Swapping two portions of a buffer.
Replacing  Replacing the text of one buffer with the text of another buffer.
Decompression  Dealing with compressed data.
Base 64  Conversion to or from base 64 encoding.
Checksum/Hash  Computing cryptographic hashes.
GnuTLS Cryptography  Cryptographic algorithms imported from GnuTLS.
Parsing HTML/XML  Parsing HTML and XML.
Parsing JSON  Parsing and generating JSON values.
JSONRPC  JSON Remote Procedure Call protocol
Atomic Changes  Installing several buffer changes atomically.
Change Hooks  Supplying functions to be run when text is changed.