fOpen (Function)

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Handling errors
Operating mode in Windows Vista (and later)
File opening mode
Multiple openings of the same file
Position in the file
Concatenating several external files
Compatibility between different versions of WINDEV/WEBDEV
Locking and unlocking
Managing UNICODE text files

WINDEV

WEBDEV

WINDEV Mobile

Others

See also

fOpen (Function)

In french: fOuvre

Open an external file (ANSI or UNICODE) to manipulate it programmatically.

Remarks:

To handle text external files, we recommend that you use fLoadText/fSaveText and fLoadBuffer/fSaveBuffer.
To handle binary external files, use fCreate or fOpen.
To open and display an external file in the associated software (to display a.DOC file in Word for example), use ShellExecute.

Example

See additional examples

// Open an external file
ResOpening is int
ResOpening = fOpen("C:\MyDirectories\File.txt", foReadWrite)
IF ResOpening <> -1 THEN 
	...
END

// Open an external file
MyExternalFile is DiskFile
MyExternalFile = fOpen("C:\MyDirectories\File.txt", foReadWrite)
IF NOT ErrorOccurred THEN
	...
END

// Open an external file
MyExternalFile is DiskFile
ResOuverture is TO boolean
ResOpening = fOpen(MyExternalFile, "C:\MyDirectories\File.txt", foReadWrite)
IF ResOpening THEN
	...
END

Syntax

Open an external file Hide the details

<Result> = fOpen(<File to manipulate> [, <Opening mode>])

<Result>: Integer or DiskFile variable

Corresponds to:
an integer:
the identifier of the external file. This identifier will be used by all the functions for handling external files.
-1 if an error occurred. To get more details on the error, use ErrorInfo with the errMessage constant.
a variable of type DiskFile. If an error occurs, the ErrorOccurred variable is set to True. To get more details on the error, use ErrorInfo with the errMessage constant.
Not available.

<File to manipulate>: Character string

Name and full or relative path of the file (up to 260 characters). A UNC path can be used.

This parameter can correspond to a full path or a path relative to the current directory (returned by fCurrentDir). This parameter is case-sensitive.
Reminder: In Android, the file system is read-only on the device and on the emulator. An application can only write to its installation directory or one of its subdirectories, as well as to the external memory (SDCard).

This parameter can correspond to a full path or a path relative to the current directory (returned by fCurrentDir). This parameter is case-sensitive.
Reminder: On iPhone or iPad, an application has the rights to write to its installation directory or one of its subdirectories

<Opening mode>: Optional constant (or combination of constants)

Constants used to define the opening mode of the file, the access mode to the file and the lock mode of the file.
File opening mode:
foAdd Opens the file in "addition" mode. At opening, the current position corresponds to the last byte of the file.
foCreate Creates the file. If the file already exists (same name, same directory), it is deleted and created again.
foCreateIfNotFound Creates the file only if it does not exist. The current position corresponds to the first byte of the file.
File access mode. This type is used by fReadLine and fWriteLine to define the type of information to read and write in the external file:
foAnsi Ansi file. This constant is used to manage an Ansi file when the "Use Unicode strings at runtime" mode is enabled in the project configuration.
Mode used by default:
in the WINDEV and WEBDEV projects earlier than version 17.
in the configurations of WINDEV and WEBDEV projects that use the "Use Ansi strings at runtime" mode from version 17.
foUnicode Unicode file. This constant is used to manage a Unicode file when the "Use ANSI strings at runtime" mode is enabled in the project configuration.
Mode used by default:
in the WINDEV Mobile projects regardless of the mode and version used.
in the configurations of WINDEV and WEBDEV projects that use the "Use Unicode strings at runtime" mode from version 17.
This constant is not available.
Mode for locking the file:
foAutomaticDeletion The file is locked when opened, and will be automatically deleted when closed (when fClose is called, or when the application is closed).
If multiple applications are using the file, it will be automatically deleted when the last application closes it (when fClose is called, or at the end of the application).
This constant is not available.
The file will not be deleted if it is being used by another application when it is closed (when fClose is called, or when the application is closed).
foRead Opens the file in "read-only" mode. This file can only be read.
foReadLock The other applications cannot read the current file.
This constant is not available.
foReadWrite
(Default value) Opens the file in "read/write" mode. This file can be read and modified (equivalent to foRead+foWrite).
foWrite Opens the file in "write-only" mode. This file can only be modified.
This constant is not available.
foWriteLock The other applications cannot modify the current file.
This constant is not available.
Other options:
foSequentialAccess Optimizes the management of caches for the file by specifying to Windows that the file will be read from the beginning to the end.
This constant is not available.

Opening an external file and initializing a DiskFile variable Hide the details

<Result> = fOpen(<DiskFile> , <File to manipulate> [, <Opening mode>])

<Result>: Boolean

True if the file was opened and associated with variable of type DiskFile,
False otherwise. To get more details on the error, use ErrorInfo with the errMessage constant.

<DiskFile>: DiskFile variable

Name of the DiskFile variable to be associated with the manipulated text file.

<File to manipulate>: Character string

Name and full or relative path of the file (up to 260 characters). A UNC path can be used.

This parameter can correspond to a full path or a path relative to the current directory (returned by fCurrentDir). This parameter is case-sensitive.
Reminder: In Android, the file system is read-only on the device and on the emulator. An application can only write to its installation directory or one of its subdirectories, as well as to the external memory (SDCard).

This parameter can correspond to a full path or a path relative to the current directory (returned by fCurrentDir). This parameter is case-sensitive.
Reminder: On iPhone or iPad, an application has the rights to write to its installation directory or one of its subdirectories

<Opening mode>: Optional constant (or combination of constants)

Constants used to define the opening mode of the file, the access mode to the file and the lock mode of the file.
File opening mode:
foAdd Opens the file in "addition" mode. At opening, the current position corresponds to the last byte of the file.
foCreate Creates the file. If the file already exists (same name, same directory), it is deleted and created again.
foCreateIfNotFound Creates the file only if it does not exist. The current position corresponds to the first byte of the file.
File access mode. This type is used by fReadLine and fWriteLine to define the type of information to read and write in the external file:
foAnsi Ansi file. This constant is used to manage an Ansi file when the "Use Unicode strings at runtime" mode is enabled in the project configuration.
Mode used by default:
in the WINDEV and WEBDEV projects earlier than version 17.
in the configurations of WINDEV and WEBDEV projects that use the "Use Ansi strings at runtime" mode from version 17.
foUnicode Unicode file. This constant is used to manage a Unicode file when the "Use ANSI strings at runtime" mode is enabled in the project configuration.
Mode used by default:
in the WINDEV Mobile projects regardless of the mode and version used.
in the configurations of WINDEV and WEBDEV projects that use the "Use Unicode strings at runtime" mode from version 17.
This constant is not available.
Mode for locking the file:
foAutomaticDeletion The file is locked when opened, and will be automatically deleted when closed (when fClose is called, or when the application is closed).
If multiple applications are using the file, it will be automatically deleted when the last application closes it (when fClose is called, or at the end of the application).
This constant is not available.
The file will not be deleted if it is being used by another application when it is closed (when fClose is called, or when the application is closed).
foRead Opens the file in "read-only" mode. This file can only be read.
foReadLock The other applications cannot read the current file.
This constant is not available.
foReadWrite
(Default value) Opens the file in "read/write" mode. This file can be read and modified (equivalent to foRead+foWrite).
foWrite Opens the file in "write-only" mode. This file can only be modified.
This constant is not available.
foWriteLock The other applications cannot modify the current file.
This constant is not available.
Other options:
foSequentialAccess Optimizes the management of caches for the file by specifying to Windows that the file will be read from the beginning to the end.
This constant is not available.

Remarks

Handling errors

fOpen throws an error in the following cases:

the file does not exist,
the file is locked by another computer or by another application,
the user has no read or write rights on the file to open.

Operating mode in Windows Vista (and later)

If this function does not work properly in Windows Vista (and later), check whether the file or directory used is not in one of the system directories (Windows directory or "Program Files" directory).

In Windows Vista (and later), with the UAC mechanism (User Account Control) enabled, you must have administrator privileges to handle and/or modify the files or directories in system directories (Windows directory or "Program Files" directory).

Programming tip: If you need to manipulate / modify files or directories, without needing administrator privileges, it is advisable:

avoid writing to the Windows directory or to the "Program Files" directory,
use the system directory of the application (returned by SysDir with the srAppDataCommun constant, for example).

File opening mode

By default, if the access mode to the file is not specified, the file is opened according to the file attribute (defined in Windows).

An error occurs if the specified access mode does not correspond to the file attribute.

A file in "read/write" mode can be opened in all the access modes supported by fOpen (foWrite, foRead and foReadWrite constants).

A file in "read-only" mode can only be opened in "read-only" mode (foRead constant).

Multiple openings of the same file

The same file can be opened several times simultaneously. Each opening is associated with a different file identifier. Each version of the file must be handled individually via its own identifier.

Position in the file

When opening a file, the current position corresponds to:

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

This position can be modified by fSeek.

Concatenating several external files

To concatenate several external files, you must:

open the destination file in "addition" mode (foAdd constant),
open the source file in "read-only" mode (foRead or foReadWrite constant),
read the source file line by line with fReadLine,
write into the destination file line by line with fWriteLine.

Compatibility between different versions of WINDEV/WEBDEV

The foText constant (opening in text mode) and the foBinary constant (opening in binary mode) are not required anymore. They are replaced with the value 0. In this case, fOpen tries to open the file in read/write mode.

Locking and unlocking

If a file is locked when opened (foReadLock or foWriteLock), it will be automatically unlocked when closed (with fClose).

Managing UNICODE text files

fOpen is used to read and write UNICODE (UTF-16 Little Endian) text files.

fOpen(<File name>, foRead + foUnicode): Opens a Unicode file. If the "Current Unicode" mark (FFFE) is found at the beginning of the file, it is automatically read.
fOpen(<File name>, foCreate + foUnicode): Creates a Unicode file. The "Current Unicode" mark (FFFE) is automatically added at the beginning of the file.
fOpen (<File name>, foCreateIfNotFound + foUnicode): Creates a Unicode file, if it doesn't exist. The "Current Unicode" mark (FFFE) is automatically added at the beginning of the file if it has been created. If the file exists and starts with the "Current Unicode" mark (FFFE), this mark is automatically read.

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