Using access modes and flags with file streams

It is possible to open a file stream on an existing file descriptor by sending the on: message to the CfsFileStream class. The on: message answers an instance of the concrete stream class corresponding to the access mode of the file descriptor. An example of converting a file descriptor into a file stream is shown below:

| fd file |

fd := CfsFileDescriptor

open: 'new.fil'

oflag: ORDWR | OCREAT | OEXCL.

fd isCfsError

ifTrue: [^self error: fd printString].

file := CfsFileStream on: fd.

"Close the file stream - this will automatically close the file

descriptor as well"

file close.

The on: message is also useful if the file is to be opened with a special share mode, using the open:oflag:share: message, which was discussed in "File locking". An example follows:

| file fd |

(fd := CfsFileDescriptor

open: 'a.fil'

oflag: ORDWR

share: ODENYRDWR) isCfsError

ifTrue: [^self error: fd message].

file := CfsFileStream on: fd.

file close.