Emacs Lisp: String Functions

Basic String Functions

length

(length SEQUENCE)
Return the length of vector, list or string SEQUENCE.

(length "abc")
;; 3

substring

(substring STRING &optional FROM TO)
return a substring from position FROM to TO. Position start at 0. By default, TO is to end of string, if omitted. FROM is 0. If negative, count from right.

(substring "abc123" 0 3)
;; "abc"

concat

(concat &rest SEQUENCES)
Concatenate all the arguments and make the result a string.

(concat "some" "thing")

split-string

(split-string STRING &optional SEPARATORS OMIT-NULLS TRIM)
Split STRING into substrings bounded by matches for SEPARATORS.

;; split string into parts, returns a list
(split-string "xy_007_cat" "_")

String To/From Number

• Emacs Lisp: Convert Int/Float, Number/String

Buffer Text to String

• Emacs Lisp: Get Buffer String

String to Buffer

• Emacs Lisp: Convert String to Buffer Text

Match String by Regex

string-match

[see Emacs Lisp: Regex Functions]

Get Regex Captured String

match-string

[see Emacs Lisp: Match Data (Regex Result)]

Regex Replace in String

replace-regexp-in-string

[see Emacs Lisp: Regex Functions]

Trim String

• string-trim-left
• string-trim-right
• string-trim

These are new in Emacs 24.4 (Released 2014-10) . Before Emacs 28 (Released 2022-04) , you need to first load (require 'subr-x) . [see Emacs Version History]

Other String Functions

To use the following, you need to first load a lib:

(require 'subr-x)

• string-blank-p
• string-empty-p
• string-join
• string-reverse
• string-remove-prefix
• string-remove-suffix
• string-pad

Strings and Characters (ELISP Manual)

String Functions Reference

Here's a complete list of string functions for reference.

• stringp
• string-or-null-p
• char-or-string-p

Predicates for Strings (ELISP Manual)

• make-string
• string → chars to string
• substring-no-properties
• concat
• split-string-default-separators

Creating Strings (ELISP Manual)

• store-substring → modify string
• clear-string

Modifying Strings (ELISP Manual)

• char-equal
• string-equal
• string-collate-equalp
• string-greaterp
• string-collate-lessp
• string-version-lessp
• string-prefix-p
• string-suffix-p
• compare-strings

• string-distance
• assoc-string

Text Comparison (ELISP Manual)

• number-to-string
• string-to-number
• char-to-string
• string-to-char
• concat
• vconcat → string into a vector
• append → string into a list
• byte-to-string

Text Comparison (ELISP Manual)

• downcase
• upcase
• capitalize
• upcase-initials

Case Conversion (ELISP Manual)

• case-table-p
• set-standard-case-table
• standard-case-table
• current-case-table
• set-case-table
• set-case-syntax-pair
• set-case-syntax-delims
• set-case-syntax
• with-case-table
• ascii-case-table
• describe-buffer-case-table

Case Tables (ELISP Manual)