<DiskFile variable>.Read (Function)

ONLINE HELP
WINDEV, WEBDEV AND WINDEV MOBILE

Version:

Home | Sign in | English

New WINDEV, WEBDEV and WINDEV Mobile 28 feature!

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

Handling errors
Position in the file

WINDEV

WEBDEV

WINDEV Mobile

Others

See also

<DiskFile variable>.Read (Function)

In french: <Variable FichierDisque>.Lit

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

// Open an external file
MyFile is DiskFile
MyFile = fOpen("C:\MyDirectories\File.txt", foReadWrite)
IF NOT ErrorOccurred THEN
// Read operation in this file
ResRead = MyFile.Read(200)
...
END

Syntax

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

<Result> = <File used>.Read(<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>: DiskFile variable

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.

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

<Result> = <File used>.Read(<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>: DiskFile variable

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

<DiskFile variable>.Read 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 <DiskFile variable>.Seek.

<DiskFile variable>.Read reads the specified elements from the current position. Once <DiskFile variable>.Read has been executed, the current position is set to the last byte read.

Remark: To always read the beginning of the file, you must call <DiskFile variable>.Seek and then <DiskFile variable>.Read.

Business / UI classification: Business Logic

Component: wd280std.dll