File Management Functions

The following functions enable sequential read / write operations in disk files:

Name Use
F_AOPEN Create or open a file in append mode
F_CLOSE Close an open file
F_COPY Copy a file
F_DELETE Remove a file
F_EOF Test if the end of the file is reached in a file that is open for reading
F_EXIST Test if a file exists
F_GETSIZE Get the size of a file
F_RENAME Rename a file
F_ROPEN Open a file for reading
F_SEEK Set the current position of a file
F_WOPEN Create or reset a file and open it for writing
FA_READ Read a DINT integer from a binary file
FA_WRITE Write a DINT integer to a binary file
FB_READ Read binary data from a file
FB_WRITE Write binary data to a file
FM_READ Read a string value from a text file
FM_WRITE Write a string value to a text file
SD_ISREADY Check that the SD card is ready for read/write
SD_MOUNT Mount an SD card
SD_UNMOUNT Unmount an SD card

F_AOPEN PLCopen motion icon

Open a file in "append" mode

ID := F_AOPEN (PATH);

PATH : STRING Name of the file. Can include a path name according to target system conventions.
ID : DINT ID of the open file or NULL if the file can't be read

If the file does not exist, it is created. If the file already exists, it is opened at the end for appending.

F_CLOSE PLCopen motion icon

Close an open file

OK := F_CLOSE (ID);

ID : DINT ID of the open file
OK : BOOL return check; TRUE if successful

F_COPYPLCopen motion icon

Copy source file contents to a destination file. Please note that large files will take a noticeable amount of time to complete. For example, a 1000KB file takes approximately 0.6 seconds. The output status is set after the file copy operation is complete.

OK := F_COPY (SRC, DST);

SRC : STRING Name of the source file (must exist). Can include a pathname according to target system conventions.
DST : STRING Name of the destination file. Can include a pathname according to target system conventions.
OK : BOOL TRUE is successful

F_DELETEPLCopen motion icon

Remove a file

OK := F_DELETE (PATH);

PATH : STRING Name of the file (must exist). Can include a pathname according to target system conventions.
OK : BOOL TRUE if successful

F_EOF PLCopen motion icon

Test if the end of a file is encountered

OK := F_EOF (ID);

ID : DINT ID of the open file
OK : BOOL TRUE if the end of the file has been encountered

F_EOF must be used only for files open in read mode by the F_ROPEN function.

F_EXISTPLCopen motion icon

Test if file exists

OK := F_EXIST (PATH);

PATH : STRING Name of the file, can include a path name according to target system conventions.
OK : BOOL TRUE if the file exists

F_GETSIZEPLCopen motion icon

Get the size of a file. Note that this function block returns 0 when the file size is zero or if the file is not present.

SIZE := F_GETSIZE (PATH);

PATH : STRING Name of the file, can include a path name according to target system conventions
SIZE : DINT Size of the file in bytes

F_RENAMEPLCopen motion icon

Rename a file

OK := F_RENAME (PATH, NEWNAME);

PATH : STRING Name of the file (must exist). Can include a pathname according to target system conventions.
NEWNAME : STRING New name for the file
OK : BOOL TRUE if successful

F_ROPEN PLCopen motion icon

Open a file for reading

Example

Structured Text

ID := F_ROPEN( PATH ) ;

Ladder Diagram


  • The positive transition on each file operation FB prevents to open the file every time the program runs (each cycle).

PATH : STRING Name of the file; the file must exist. Can include a path name according to target system conventions.
ID : DINT ID of the open filer NULL if the file can't be read

F_SEEKPLCopen motion icon

Set the current position in an open file

OK := F_SEEK (ID, POS, ORG);
ID DINT ID of an open file
POS DINT Number of bytes to offset from ORG.
If ORG = SEEK_SET, then POS should be ≥ 0
If ORG = SEEK_END, then POS should be ≤ 0
If ORG = SEEK_CUR, then POS can be positive or negative
ORG DINT Origin of the move:
SEEK_SET = 0 - beginning of the file
SEEK_CUR = 1 - current position
SEEK_END = 2 - end of the file
OK BOOL return check: TRUE if successful

F_WOPEN PLCopen motion icon

Open a file for writing

ID := F_WOPEN (PATH);

PATH : STRING Name of the file. Can include a path name according to target system conventions.
ID : DINT ID of the open file or NULL if the file can't be read

If the file does not exist, it is created. If the file already exists, its contents are cleared.

FA_READ PLCopen motion icon

Read a DINT value from a file

Q := FA_READ (ID);

ID: DINT ID of a file open for reading
Q : DINT read value or 0 in case of error

This function reads an integer values from a file. Integer values read by FA_READ must have been written by the FA_WRITE function. Integers are stored in binary format in the file, using memory conventions of the target system. After the file is opened, the first call to FA_READ will read the first integer data, the second call will read the next, etc. To re-start reading at the beginning of the file, close the file and re-open it.

FA_WRITE PLCopen motion icon

Write a DINT value to a file

OK := FA_WRITE (ID, IN);

ID : DINT ID of a file open for writing
IN : DINT integer value to be written
OK : BOOL return check; TRUE if successful

Integers are stored in binary format in the file, using memory conventions of the target system.

FB_READ PLCopen motion icon

Read binary data from a file

OK := FB_READ (ID, V);

ID : DINT ID of a file open for writing
V : ANY variable to be read; cannot be a string.
OK : BOOL return check; TRUE if successful

This function reads binary data from a file. Variables are stored in binary format in the file, using memory conventions of the target system. After the file is opened, the first call to FB_READ will read the first binary data, the second call will read the next, etc. To re-start reading at the beginning of the file, close the file and re-open it.

FB_WRITEPLCopen motion icon

Write binary data to a file

OK := FB_WRITE (ID, V);

ID : DINT ID of a file open for writing
V : ANY variable to be written; cannot be a string.
OK : BOOL return check; TRUE if successful

Variables are stored in binary format in the file, using memory conventions of the target system.

FM_READ PLCopen motion icon

Read a string value from a file

Q := FM_READ (ID);

ID : DINT ID of a file open for reading
Q : STRING read value or empty string in case of error

This function reads a string from a file. After the file is opened, the first call to FM_READ will read the first line of text, the second call will read the next line of text, etc. The maximum string length is defined by either the maximum length for the return variable or when the EOL (end of line) character is encountered, which ever occurs first. Close the file and reopen it to restart reading it at the beginning.

FM_WRITE PLCopen motion icon

Write a string value to a file

OK := FM_WRITE (ID, IN);

ID : DINT ID of a file open for writing
IN : STRING string value to be written
OK : BOOL return check; TRUE if successful

This function writes a text line in the file. End of line character is systematically written after the input string.

String Escape Sequences

For greater formatting control over your STRING output, you may escape the STRING by prepending a $ and use a pre-defined sequence. This is called a string escape sequence.

Escape Sequence Result
$$ $
$' '
$L linefeed
$N newline
$P page (form feed)
$R return
$T tab
$xx hex value

The following is an example of how STRING escape sequences can be used. 

ID:=F_WOPEN('c:\ myfile.txt');
WOK:=FM_WRITE(ID,'123456$N');
//WOK:=FM_WRITE(ID,'$N');
WOK:=FM_WRITE(ID,'abcd$N');
WOK:=FM_WRITE(ID,'the end');
WOK:=F_Close(ID);

The example outputs a file which reads:

123456
abcd
the end

SD_MOUNTPLCopen motion icon

Mount the SDCard on the PDMM. This will not perform any action, and always return TRUE with a Simulator.

OK := SD_MOUNT();
OK : BOOL TRUE if mounting SDCard is successful

  • Before performing, make sure the SDCard is inserted.


  • It is recommended that SD_MOUNT be used only when motion is not started.

SD_UNMOUNTPLCopen motion icon

Un-mount the SDCard from the PDMM. This will not perform any action, and always return TRUE with a Simulator.

OK := SD_UNMOUNT();
OK : BOOL TRUE if un-mounting SDCard is successful

  • It is recommended that SD_UNMOUNT be used only when motion is not started.

SD_ISREADYPLCopen motion icon

Verify if the SDCard is mounted on the PDMM. This will verify if the SDCard folder is available inside the userdata folder when using a Simulator.

OK := SD_ISREADY();
OK : BOOL TRUE if the SDCard is mounted (PDMM / PCMM)