Raspberry PI-FILE WRITE

2020-02-27T13:47:44.896000Z

You have two options that I know of.
1. Write an empty string to the file using the mwrite mode. This will overwrite and clear the files contents.
2. Delete the file and create a new one.

Raspberry PI-FILE WRITE

2020-02-27T13:47:44.738000Z

Hello,

I am trying to write to file, where I want to write my data to several lines and not only one line, and my code is doing that now.

Also I want to delete all the data from file on rising edge of the tag. Any Ideas how to do that?

VAR
( Set xDemoStart to TRUE to start test )
xDemoStart: BOOL:=FALSE;
uiDemoStatus: UINT:=0;

filestring:     STRING:='uuuHello this is a test';
fileCR:         STRING:='$r$n';
endline:        STRING:='$r';
(*  
sFileName is file location relative to the CODESYS Runtime directory on the HMI
examples:
    'test.txt'                          File is saved in 'Flash\QtHMI\RTS' 
    '..\test.txt'                       File is saved in 'Flash\QtHMI' 
    '..\data\test.txt'                  File is saved in 'Flash\QtHMI\data' 
    '..\..\..\USBMemory\test.txt'       File is saved in root of external USB memory
    '..\..\..\Storage Card\test.txt'    File is saved in external SD Card memory
*)

filemode:       BYTE:=2;
(*
Mode in which the file should be opened,
FILE.MWRITE (0): Write access; File will be overwritten/created
FILE.MREAD (1): Read access; File will be opened for reading only
FILE.MRDWR (2): Read/write access; File will be overwritten/created
FILE.MAPPD (3): Write access; Data will be appended at the end of the file
*)

filename:       CAA.FILENAME:='/home/pi/DataLogger/INTHISA_KUZMA11.csv';
hFile:          CAA.HANDLE;
filesize1:      CAA.SIZE:=0;
filesize2:      CAA.SIZE:=0;
fileopen:       FILE.Open;
filewrite:      FILE.Write;
fileread:       FILE.Read;
fileclose:      FILE.Close;

filestringwrite: STRING(255);

END_VAR

CASE uiDemoStatus OF
0: ( Start demo )
IF xDemoStart THEN
uiDemoStatus:=1;
END_IF
fileopen(xExecute:=FALSE);
filewrite(xExecute:=FALSE);
fileread(xExecute:=FALSE);
fileclose(xExecute:=FALSE);

1: ( create a new file )
fileopen.sFileName:=filename;
fileopen.eFileMode:= filemode;
fileopen.xExclusive:=TRUE;
fileopen(xExecute:=TRUE);
IF fileopen.xDone THEN
hFile:=fileopen.hFile;
uiDemoStatus:=uiDemoStatus+1;
END_IF
IF fileopen.xError THEN
( error handling)
;
END_IF

2: ( write text in the file )

filestringwrite:=CONCAT(filestring,fileCR);
filewrite.hFile:=hFile;
filewrite.pBuffer:=ADR(filestringwrite);
filesize1:=SIZEOF(filestringwrite);
filewrite.szSize:=filesize1;
filewrite.udiTimeOut:=100000;                     (* 100ms Timeout *)
filewrite(xExecute:=TRUE);
IF filewrite.xDone THEN
    uiDemoStatus:=uiDemoStatus+2;
END_IF
IF filewrite.xError THEN
    uiDemoStatus:=0;
    ;
END_IF

3: ( read file)
fileread.hFile:=hFile;
fileread.udiTimeOut:=100000; ( 100ms Timeout )
fileread.pBuffer:=ADR(FileString);
fileread.szBuffer:=255;
fileread(xExecute:=TRUE);
IF fileread.xDone THEN
filesize2:=fileread.szSize;
IF filesize2 = filesize1 THEN
uiDemoStatus:=uiDemoStatus+1;
ELSE
uiDemoStatus:=uiDemoStatus+1;
;
END_IF
END_IF
IF fileread.xError THEN
uiDemoStatus:=uiDemoStatus+2;
;
END_IF

4: ( close file)
fileclose.hFile:=hFile;
fileclose(xExecute:=TRUE);
IF fileclose.xDone THEN
uiDemoStatus:=uiDemoStatus+1;
END_IF
IF fileclose.xError THEN
( error handling)
;
END_IF

5: ( end of example )
xDemoStart:=FALSE;
uiDemoStatus:=0;

END_CASE

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