Elisp: String Functions

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

• concat
• format
• mapconcat
• byte-to-string

• Elisp: Join Strings, Codepoints to String

Convert String and Number

• string-to-number
• number-to-string
• format

• Elisp: Convert Number, String
• Elisp: Format String

Convert String to Codepoints

• vconcat → string to vector of codepoints.
• append → string to list of codepoints.

• Elisp: Sequence. Join, Convert

Split String (String to List)

split-string

(split-string STRING &optional SEPARATORS OMIT-NULLS TRIM)

• Split STRING
• Return a list.
• SEPARATORS is a Elisp: Regular Expression

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

Buffer Text to String

• Elisp: Get Buffer String

String to Buffer

• Elisp: Convert String to Buffer Text

Check If Contains a Pattern, Find Index of Substring

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

• Elisp: Match Data (Regex Result)

Replace in String

• string-replace
• replace-regexp-in-string

• Elisp: Replace String or Regex in String

Trim String

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

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

• Elisp: String Comparison, Equality, Order

Character and String

• Elisp: Character Type

Other String Functions

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

(require 'subr-x)

• string-blank-p → is empty or whitespace.
• string-empty-p → is empty.
• string-join → join with separators.
• string-reverse (obsolete. use reverse)
• string-remove-prefix
• string-remove-suffix
• string-pad

Misc String Functions

• stringp → is string
• string-or-null-p

• make-string
• substring-no-properties
• split-string-default-separators → variable

• store-substring → modify string
• clear-string

• assoc-string

Letter Case

• downcase
• upcase
• capitalize
• upcase-initials

Case Table

• 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

Reference

• String Type (ELISP Manual)