LEFT

Copy characters from the left

LEFT copies, starting from the left, n characters of the string of the first input variable to the output variable. You define the number of characters L to be delivered by the second input variable.

Parameters

Input

IN (STRING): input string
L (INT): number of input string's characters that are copied, from the left

Output

Unnamed output (STRING): copied string

Remarks

If this instruction is used with UTF-8 strings, please refer to the notes concerning UTF-8 strings under the data type STRING.
If the number of characters to be delivered is greater than the input string, the complete string will be copied to the output variable output_string.
If the output string is longer than the length defined for the output variable in the field “Type”, only as many characters are copied as the output variable can hold.The system variable sys_bIsCarry is set.

Error flags

sys_bIsOperationErrorHold (turns to TRUE and remains TRUE): if a string applied at the input or output is an invalid string
sys_bIsOperationErrorNonHold (turns to TRUE for one scan): if a string applied at the input or output is an invalid string
sys_bIsCarry (turns to TRUE for one scan): if the output string is longer than the length defined for the output variable in the field "Type"

Example

POU header

All input and output variables used for programming this function have been declared in the POU header. The same POU header is used for all programming languages.

	VAR
		input_string: STRING[15]:='Ideas for life';
			(*sample string*)
		output_string: STRING[5]:='';
			(*result: here 'Ideas'*)
		character_number: INT:=5;
			(*characters to be delivered*)
	END_VAR

In this example the input variables (input_string and character_number) have been declared. Instead, you may enter the string ('Ideas for life') and the number of characters to be delivered directly into the function. The string has to be put in inverted commas, both in the POU header and in the function.

POU body

Starting from the left, character_number (5) of input_string ('Ideas for life’) is copied to output_string ('Ideas’).

LD body

BODY
    WORKSPACE
        NETWORK_LIST_TYPE := NWTYPELD ;
        ACTIVE_NETWORK := 0 ;
    END_WORKSPACE
    NET_WORK
        NETWORK_TYPE := NWTYPELD ;
        NETWORK_LABEL :=  ;
        NETWORK_TITLE :=  ;
        NETWORK_HEIGHT := 4 ;
        NETWORK_BODY
B(B_F,LEFT!,Instance,11,0,16,4,,?DIN?DL?C);
B(B_VARIN,,input_string,9,1,11,3,);
B(B_VARIN,,character_number,9,2,11,4,);
B(B_VAROUT,,output_string,16,1,18,3,);
L(1,0,1,4);
        END_NETWORK_BODY
    END_NET_WORK
END_BODY

ST body

output_string:=LEFT(IN:=input_string, L:=character_number);

IL body

LD	input_string
LEFT	character_number
ST	output_string