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(libc.info)File Status Flags

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File Status Flags
=================

   "File status flags" are used to specify attributes of the opening of
a file.  Unlike the file descriptor flags discussed in Note: Descriptor
Flags, the file status flags are shared by duplicated file descriptors
resulting from a single opening of the file.  The file status flags are
specified with the FLAGS argument to `open'; Note: Opening and Closing
Files.

   File status flags fall into three categories, which are described in
the following sections.

   * Note: Access Modes, specify what type of access is allowed to the
     file: reading, writing, or both.  They are set by `open' and are
     returned by `fcntl', but cannot be changed.

   * Note: Open-time Flags, control details of what `open' will do.
     These flags are not preserved after the `open' call.

   * Note: Operating Modes, affect how operations such as `read' and
     `write' are done.  They are set by `open', and can be fetched or
     changed with `fcntl'.

   The symbols in this section are defined in the header file `fcntl.h'.

Access Modes

Whether the descriptor can read or write.

Open-time Flags

Details of `open'.

Operating Modes

Special modes to control I/O operations.

Getting File Status Flags

Fetching and changing these flags.