Attention

IronPLC implements many parts of the IEC 61131-3 standard and is working toward full Structured Text support. Key features still missing include structures and user defined function blocks.

STRING¶

Single-byte character string with a maximum length.

Size	Variable (default max 254 characters)
Default	`''` (empty string)
IEC 61131-3	Section 2.3.1
Support	Not yet supported

Literals¶

'Hello, world!'
'It''s escaped'
STRING#'typed literal'

The maximum length can be specified in the declaration:

VAR
    name : STRING[50];   (* max 50 characters *)
    msg  : STRING;       (* default max length *)
END_VAR

Constant Length (Vendor Extension)¶

Note

This is a vendor extension not part of the IEC 61131-3 standard. See Enabling Dialects and Features for how to enable it.

With the --allow-constant-type-params flag (or --allow-all), you can use a global constant for the maximum length instead of a literal:

VAR_GLOBAL CONSTANT
    MAX_NAME_LEN : INT := 50;
END_VAR

FUNCTION_BLOCK fb1
    VAR_EXTERNAL CONSTANT
        MAX_NAME_LEN : INT;
    END_VAR
    VAR
        name : STRING[MAX_NAME_LEN];
    END_VAR
END_FUNCTION_BLOCK

STRING¶

Literals¶

Constant Length (Vendor Extension)¶

See Also¶