FileOpen
Open an existing file and return a file handle
Declaration
Source position: filutilh.inc line 171
Description
FileOpen opens a file with name FileName with mode Mode. Mode can be one of the following constants:
- fmOpenRead
- Open file in read-only mode
- fmOpenWrite
- Open file in write-only mode
- fmOpenReadWrite
- Open file in read/write mode.
Under Windows and Unix, the above mode can be or-ed with one of the following sharing/locking flags:
- fmShareCompat
- Open file in DOS share-compatibility mode
- fmShareExclusive
- Lock file for exclusive use
- fmShareDenyWrite
- Lock file so other processes can only read.
- fmShareDenyRead
- Lock file so other processes cannot read.
- fmShareDenyNone
- Do not lock file.
If the file has been successfully opened, it can be read from or written to (depending on the Mode parameter) with the FileRead and FileWrite functions.
Remark:
Remark that you cannot open a file if it doesn't exist yet, i.e. it will not be created for you. If you want tp create a new file, or overwrite an old one, use the
FileCreate function.
There are some limitations to the sharing modes.
- Sharing modes are only available on Unix and Windows platforms.
- Unix only support sharing modes as of 2.4.0.
- fmShareDenyRead only works under Windows at this time, and will always result in an error on Unix platforms because its file locking APIs do not support this concept.
- File locking is advisory on Unix platforms. This means that the locks are only checked when a file is opened using a file locking mode. In other cases, existing locks are simply ignored. In particular, this means that fmShareDenyNone has no effect under Unix, because this can only be implemented as ``use no locking'' on those platforms. As a result, opening a file using this mode will always succeed under Unix as far as the locking is concerned, even if the file has already been opened using fmShareExclusive.
- Under Solaris, closing a single file handle associated with a file will result in all locks on that file (even via other handles) being destroyed due to the behaviour of the underlying API (fcntl). Because of the same reason, on Solaris you cannot use fmShareDenyWrite in combination with fmOpenWrite, nor fmShareExclusive in combination with fmOpenRead although both work with fmOpenReadWrite.
For an example, see FileCreate
Errors
On Error, THandle(-1) is returned.
See also
FileWrite
Write data from a buffer to a given file handle.
FileCreate
Create a new file and return a handle to it.
FileRead
Read data from a file handle in a buffer.
FileSeek
Set the current file position on a file handle.
Documentation generated on: May 14 2021