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authorFred Drake <fdrake@acm.org>2001-05-09 21:09:57 (GMT)
committerFred Drake <fdrake@acm.org>2001-05-09 21:09:57 (GMT)
commitd0de57cfbb7001a15935d09bddf3ef696956b32a (patch)
treef78d503e89990cafc5a4f8fbf79b603756732ed8
parent152a25ee1c55e200edf672aa3d6c5b1a061c6c8f (diff)
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Update the fcntl module documentation.
-rw-r--r--Doc/lib/libfcntl.tex56
1 files changed, 26 insertions, 30 deletions
diff --git a/Doc/lib/libfcntl.tex b/Doc/lib/libfcntl.tex
index 7c357e6..d02eaa5 100644
--- a/Doc/lib/libfcntl.tex
+++ b/Doc/lib/libfcntl.tex
@@ -11,8 +11,12 @@
This module performs file control and I/O control on file descriptors.
It is an interface to the \cfunction{fcntl()} and \cfunction{ioctl()}
-\UNIX{} routines. File descriptors can be obtained with the
-\method{fileno()} method of a file or socket object.
+\UNIX{} routines.
+
+All functions in this module take a file descriptor \var{fd} as their
+first argument. This can be an integer file descriptor, such as
+returned by \code{sys.stdin.fileno()}, or a file object, such as
+\code{sys.stdin} itself.
The module defines the following functions:
@@ -20,22 +24,22 @@ The module defines the following functions:
\begin{funcdesc}{fcntl}{fd, op\optional{, arg}}
Perform the requested operation on file descriptor \var{fd}.
The operation is defined by \var{op} and is operating system
- dependent. Typically these codes can be retrieved from the library
- module \module{FCNTL}\refstmodindex{FCNTL}. The argument \var{arg}
- is optional, and defaults to the integer value \code{0}. When
- present, it can either be an integer value, or a string. With
- the argument missing or an integer value, the return value of this
- function is the integer return value of the C \cfunction{fcntl()}
- call. When the argument is a string it represents a binary
- structure, e.g.\ created by \function{struct.pack()}. The binary
- data is copied to a buffer whose address is passed to the C
- \cfunction{fcntl()} call. The return value after a successful call
- is the contents of the buffer, converted to a string object. The length
- of the returned string will be the same as the length of the \var{arg}
- argument. This is limited to 1024 bytes. If the information returned
- in the buffer by the operating system is larger than 1024 bytes,
- this is most likely to result in a segmentation violation or a more
- subtle data corruption.
+ dependent. These codes are also found in the \module{fcntl}
+ module. The argument \var{arg} is optional, and defaults to the
+ integer value \code{0}. When present, it can either be an integer
+ value, or a string. With the argument missing or an integer value,
+ the return value of this function is the integer return value of the
+ C \cfunction{fcntl()} call. When the argument is a string it
+ represents a binary structure, e.g.\ created by
+ \function{struct.pack()}. The binary data is copied to a buffer
+ whose address is passed to the C \cfunction{fcntl()} call. The
+ return value after a successful call is the contents of the buffer,
+ converted to a string object. The length of the returned string
+ will be the same as the length of the \var{arg} argument. This is
+ limited to 1024 bytes. If the information returned in the buffer by
+ the operating system is larger than 1024 bytes, this is most likely
+ to result in a segmentation violation or a more subtle data
+ corruption.
If the \cfunction{fcntl()} fails, an \exception{IOError} is
raised.
@@ -90,26 +94,18 @@ The default for \var{start} is 0, which means to start at the
beginning of the file. The default for \var{length} is 0 which means
to lock to the end of the file. The default for \var{whence} is also
0.
-
\end{funcdesc}
-If the library modules \module{FCNTL}\refstmodindex{FCNTL} or
-\module{IOCTL}\refstmodindex{IOCTL} are missing, you can find the
-opcodes in the C include files \code{<sys/fcntl.h>} and
-\code{<sys/ioctl.h>}. You can create the modules yourself with the
-\program{h2py} script, found in the \file{Tools/scripts/} directory.
-
-
Examples (all on a SVR4 compliant system):
\begin{verbatim}
-import struct, fcntl, FCNTL
+import struct, fcntl
file = open(...)
-rv = fcntl(file.fileno(), FCNTL.F_SETFL, FCNTL.O_NDELAY)
+rv = fcntl(file, fcntl.F_SETFL, os.O_NDELAY)
-lockdata = struct.pack('hhllhh', FCNTL.F_WRLCK, 0, 0, 0, 0, 0)
-rv = fcntl.fcntl(file.fileno(), FCNTL.F_SETLKW, lockdata)
+lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 0, 0, 0)
+rv = fcntl.fcntl(file, fcntl.F_SETLKW, lockdata)
\end{verbatim}
Note that in the first example the return value variable \var{rv} will