CONTROL
- Introduction to CTRL
- CONTROL Classes
- Types of Control Functions
- CONTROL graphics
- CONTROL Functions
  - Funtions A
  - Funtions B
  - Funtions C
  - Funtions D
  - Functions E
  - Functions F
    - fclose()
      Closes a file.
    - folderSelector()
      Opens the folder selector dialog and writes the name of the selected folder to the string variable "path".
    - fileSelector()
      Opens the file selection dialog and writes the selected file name to fileName.
    - fscanfPL()
      Reads a file similar to fscanf() except changes to the current WinCC OA language before converting.
    - floor()
      Rounds down to an integer.
    - findExecutable()
      The function searches for the given executable and returns the full path to it or an empty string if not found.
    - fwrite()
      Writes a number of bytes from a blob variable to a file.
    - fprintfPL()
      Writes to a file similar to fprintf() except changes to the current WinCC OA language before converting.
    - fseek()
      Sets the pointer of the file f from the position whence to the position defined by the offset.
    - formatTimeUTC()
      Returns the UTC time in a particular format.
    - fabs()
      Returns the absolute value of x.
    - fflush()
      Writes data to a file.
    - fprintf()
      Writes to a file.
    - fswAddPath()
      The functions add a path for monitoring to the FileSystemWatcher.
    - formatDebug()
      Similar to the function Debug() but instead of writing to the log viewer returns the debug messages as string,.
    - fmod()
    - formatTime()
      Returns the time in a particular format.
    - fscanf()
      Reads a file.
    - fillSelector()
      Opens the filling pattern selector and writes the selection to a variable.
    - fileToString()
      This function loads an ASCII file and writes the contents into a string variable.
    - fontSelector()
      Opens the font type selector and writes the selection to a variable.
    - fopen()
      Opens a file.
    - feof()
      Examines whether an end of file has been noted.
    - formatSelector()
      Opens the format selector and writes the string format that has been selected on the format string variable.
    - fread()
      Reads a number of bytes from a file to a blob variable.
    - fscanfUL()
      Reads a file like fscanf(), but change to the current Windows user language before converting.
    - fileEditor()
      Opens text files such as .txt and .doc files in an editor. You can edit both plain and rich text.
    - fputs()
      Writes a string to a file.
    - fprintfUL()
      Writes to a file similar to fprintf() except changes to the current Windows user language before converting.
    - fgets()
      Returns a string from a file.
    - ftell()
      The ftell function obtains the current value of the file position indicator for the stream pointed to by f.
    - ferror()
      Examines whether a file error has been noted.
    - fswRemovePath()
      The function removes a path from the monitoring of the FileSystemWatcher.
  - Functions G
  - Functions H
  - Functions I
  - Functions J
  - Functions K
  - Functions L
  - Functions M
  - Functions N
  - Functions O
  - Functions P
  - Functions Q
  - Functions R
  - Functions S
  - Functions T
  - Functions U
  - Functions V
  - Functions W
  - Functions X
  - Functions Y
  - Functions Z
- CTRL Debugger
  With the CTRL Debugger you can debug the programming language Control.

fread()

Reads a number of bytes from a file to a blob variable.

Synopsis

int fread(file f, blob &b[, int numBytes]);

Parameters


Parameters	Meaning
f	File to be read
b	blob variable
numBytes	Number of bytes to be read. This argument is optional, if it is not given all bytes until EOF are read.

Return value

In the event of errors, the function returns -1 or EOF otherwise, the number of read characters.

Description

Reads a number of bytes from a file to a blob variable.

Example

Writes 4 bytes and reads 2 bytes to/from a file.

 main()
{
  blob target, rtarget;
  int len, pos;
  string s;
  anytype value;
  bool bigendian;
  s = "FFAB003AFF";
  target = s;
  DebugN(target);
  len = 1;
  value = 5;
  bigendian = TRUE;
  DebugN("Blob AppendValue: " + blobAppendValue(target, value, len, bigendian)); //blob length is 6 = FF AB 0 3A FF 5
  DebugN(target); //ff ab 0 3a ff 5
  int fr, fw, numW, fcl, err, numR;
  file wf;
  wf = fopen("D:\\BFile.txt", "w");
  numR = 2;
  numW = 4;
  err = ferror(wf);
  fw = fwrite(wf, target, numW);
  DebugN("Number of bytes that could be written:", fw);
  //Output: ["Number of bytes that could be written:"][4]
  fr = fread(wf, rtarget, numR);
  DebugN("Number of bytes that could be read:", fr);
  //Output: ["Number of bytes that could be read:"][2]
  fcl = fclose(wf);
}

Assignment

File functions

Availability

CTRL