CODESYS MID

MID is a string function in the CODESYS Standard library that returns a specified number of characters from a string, starting from a given position. It is called as MID(STR, LEN, POS): take LEN characters from STR beginning with the character at position POS, and return the partial string. The function is declared as FUNCTION MID : STRING(255).

Source checked12/12 values · 2026-10-26

Specification

2 sources

Language	iec 61131 3
Code	MID
Group	String Functions
Syntax	MID (STR, LEN, POS)
Dialect	CODESYS

Parameters

Name	Data type	Description
STR	STRING(255)	String to be analyzed
LEN	INT	Number of characters, counted from the left
POS	INT	Start position for the partial string

Study notes

Declared as FUNCTION MID : STRING(255), so the returned partial string can be up to 255 characters.
All three arguments are inputs: STR (STRING(255)), LEN (INT) and POS (INT).
The source example VarSTRING1 := MID('SUSI',2,2); returns 'US'.
LEN is documented as the number of characters, counted from the left; POS is the start position for the partial string.