fRead (Function)

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External file management functions

Constants for the external files

Functions for handling directories and external files

Handling the external files

Storing files in Android

Summary table: Managing the application directories according to the platform

fDetectRemovableStorage

fInsertTextAtBeginning

fReadLineRegularExpression

fRemoveDir

fRename

fReportsAndQueriesDir

Managing errors
Position in the file

WINDEV

WEBDEV

WINDEV Mobile

Others

See also

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.

Versions 15 and later

This function is now available for Android applications.

New in version 15

This function is now available for Android applications.

Versions 16 and later

This function is now available for Windows Phone applications.

New in version 16

This function is now available for Windows Phone applications.

Versions 17 and later

This function is now available for iPhone/iPad applications.

New in version 17

This function is now available for iPhone/iPad applications.

Versions 18 and later

This function is now available in Android widget mode.

This function is now available in Windows Store apps mode.

New in version 18

This function is now available in Android widget mode.

This function is now available in Windows Store apps mode.

This function is now available in Android widget mode.

This function is now available in Windows Store apps mode.

Versions 21 and later

This function is now available in Universal Windows 10 App mode.

New in version 21

This function is now available in Universal Windows 10 App mode.

Example

See additional examples

// Open an external file
FileID = fOpen("C:\MyDirectories\File.txt", foReadWrite)
IF FileID <> -1 THEN
// Read operation in this file
ResRead = fRead(FileID, 200)
...
END

Syntax

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

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

<Result>: Character string

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

<File identifier>: Integer

Identifier of the file to use, defined by fOpen or fCreate.
This parameter must be a variant.

<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 identifier> , <Number of bytes to read> , <Address>)

<Result>: Integer

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

<File identifier>: Integer

Identifier of the file to use, defined by 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

Managing 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,
therefore, the end of file is reached.

Position in the file

When opening a file, the current position corresponds to:

the first byte of the file (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 run, the current position corresponds to the last byte read.

Remark: To always read the beginning of the file, you must call fSeek and then fRead.

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

Component: wd270std.dll