fRead (Function)

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Help / WLanguage / WLanguage functions / Standard functions / External file functions

Handling errors
Position in the file

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fRead (Function)

In french: fLit

Reads a block of bytes in an external file.

In this version, you can only read a character string from an external file in ANSI format.

Example

See additional examples

// Ouverture d'un fichier externe
IDFichier is int
ResLecture is int
IDFichier = fOpen("C:\MesRépertoires\Fichier.txt", foReadWrite)
IF IDFichier <> -1 THEN
	// Lecture dans ce fichier
	ResLecture = fRead(IDFichier, 200)
	...
END

// Ouverture d'un fichier externe
MonFichierTxt is DiskFile
ResLecture is int
MonFichierTxt = fOpen("C:\MesRépertoires\Fichier.txt", foReadWrite)
IF NOT ErrorOccurred THEN
	// Lecture dans ce fichier
	ResLecture = fRead(MonFichierTxt, 200)
	...
END

Syntax

Reading a block of bytes in an external file Hide the details

<Result> = fRead(<File used> , <Number of bytes to read>)

<Result>: Character string

Block of bytes that was read.
Empty string ("") if an error occurred. To get more details on the error, use ErrorInfo with the errMessage constant.

<File used>: Integer or DiskFile variable

Identifier of the file to use, defined by fOpen or fCreate.
Name of variable of type DiskFile initialized with function fOpen or fCreate..
Not available.

<Number of bytes to read>: Integer

Number of bytes to read (up to 2 147 483 648 bytes).
If the data is a Unicode string, the number of bytes to read corresponds to:
in UTF16: the number of characters multiplied by 2.
in UTF32: the number of characters multiplied by 4.

Reading the content of an external file and assigning it to a memory area (identified by its address) Hide the details

<Result> = fRead(<File used> , <Number of bytes to read> , <Address>)

<Result>: Integer

Number of bytes read,
0 if an error occurs. To get more details on the error, use ErrorInfo with the errMessage constant.

<File used>: Integer or DiskFile variable

Identifier of the file to use, defined by fOpen or fCreate.
Name of the DiskFile variable initialized with fOpen or fCreate.

<Number of bytes to read>: Integer

Number of bytes to read (up to 2 147 483 648 bytes).
If the data is a Unicode string, the number of bytes to read corresponds to:
in UTF16: the number of characters multiplied by 2.
in UTF32: the number of characters multiplied by 4.

<Address>: Address

Address of affected memory section.

Remarks

Handling errors

fRead throws an error in the following cases:

the file is not opened,
the file is not accessible in read mode,
the file is locked by another computer or by another application,
the end of the file has been reached.

Position in the file

When opening a file, the current position corresponds to:

the first file byte (by default),
the last byte of the file is the file is opened in "addition" mode (foAdd constant).

This position can be modified by fSeek.

fRead reads the specified elements from the current position. Once fRead has been executed, the current position is set to the last byte read.

Note: To always read the beginning of the file, use the fSeek function followed by the fReadfunction. .

Related Examples:

Unit examples (WINDEV): Handling text files

[ + ] Handling "text" files with WINDEV:
- Create a text file
- Write into a text file
- Read in a text file

Unit examples (WEBDEV): Handling text files

[ + ] This example explains how to handle "non HFSQL" files with WEBDEV and it allows you to:
- Create a text file
- Write into a text file
- Read in a text file

Unit examples (WINDEV Mobile): Handling text files

[ + ] Handling external "text" files:
- Create a text file
- Write into a text file
- Read in a text file

Business / UI classification: Business Logic

Component: wd300std.dll