Elisp: String Functions

By Xah Lee. Date: . Last updated: .

Length, Substring

length
(length SEQUENCE)

Return the length of a 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, and FROM is 0. If negative, count from right.

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

Join Strings, Convert to String

Convert String and Number

Convert String to Codepoints

Split String (String to List)

split-string
(split-string STRING &optional SEPARATORS OMIT-NULLS TRIM) 
;; split string into parts, return a list
(split-string "xy_007_cat" "_")

Buffer Text to String

String to Buffer

Check If Contains a Pattern, Find Index of Substring

string-search

(string-search search Str &optional START-POS)

Find search in Str. If found, return the index of first occurrence, else return nil. 

(string-search "ab" "ttabtt" )
;; 2

(string-search "ab" "ttt" )
;; nil
string-match
(string-match REGEXP STRING &optional START)

Return the index of beginning of first match in STRING. Return nil if no match.

(let ((case-fold-search t))
  (string-match "3" "xx3x"))
;; 2

Get Regex Captured String

match-string

Replace in String

Trim String

These are new in Emacs 24.4 (date 2014-10) . Before Emacs 28 (date 2022) , you need to first load (require 'subr-x) .

String Comparison, Equality Test

Character and String

Other String Functions

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

(require 'subr-x)

Misc String Functions

Letter Case

Case Table

Reference

Elisp, String