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This commit is contained in:
Michael Kerrisk 2007-12-23 22:20:16 +00:00
parent 218dfacd71
commit 7670ac9d8e
2 changed files with 16 additions and 14 deletions
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26
man2/select_tut.2
View File

@ -365,8 +365,8 @@ subtle errors that will remove the advantage of using
hence I will present a list of essentials to watch for when using the hence I will present a list of essentials to watch for when using the
.BR select () .BR select ()
call. call.
.TP .TP 4
\fB1.\fP 1.
You should always try to use You should always try to use
.BR select () .BR select ()
without a timeout. without a timeout.
@ -375,11 +375,11 @@ should have nothing to do if there is no data available.
Code that Code that
depends on timeouts is not usually portable and is difficult to debug. depends on timeouts is not usually portable and is difficult to debug.
.TP .TP
\fB2.\fP 2.
The value \fInfds\fP must be properly calculated for efficiency as The value \fInfds\fP must be properly calculated for efficiency as
explained above. explained above.
.TP .TP
\fB3.\fP 3.
No file descriptor must be added to any set if you do not intend No file descriptor must be added to any set if you do not intend
to check its result after the to check its result after the
.BR select () .BR select ()
@ -387,7 +387,7 @@ call, and respond
appropriately. appropriately.
See next rule. See next rule.
.TP .TP
\fB4.\fP 4.
After After
.BR select () .BR select ()
returns, all file descriptors in all sets returns, all file descriptors in all sets
@ -397,7 +397,7 @@ should be checked to see if they are ready.
.\" for writing \fImust\fP be written to, and any file descriptor .\" for writing \fImust\fP be written to, and any file descriptor
.\" available for reading \fImust\fP be read, etc. .\" available for reading \fImust\fP be read, etc.
.TP .TP
\fB5.\fP 5.
The functions The functions
.BR read (2), .BR read (2),
.BR recv (2), .BR recv (2),
@ -413,7 +413,7 @@ always going to be the case.
You should cope with the case of your You should cope with the case of your
functions only managing to send or receive a single byte. functions only managing to send or receive a single byte.
.TP .TP
\fB6.\fP 6.
Never read/write only in single bytes at a time unless your are really Never read/write only in single bytes at a time unless your are really
sure that you have a small amount of data to process. sure that you have a small amount of data to process.
It is extremely It is extremely
@ -421,7 +421,7 @@ inefficient not to read/write as much data as you can buffer each time.
The buffers in the example above are 1024 bytes although they could The buffers in the example above are 1024 bytes although they could
easily be made larger. easily be made larger.
.TP .TP
\fB7.\fP 7.
The functions The functions
.BR read (2), .BR read (2),
.BR recv (2), .BR recv (2),
@ -445,7 +445,7 @@ set non-blocking I/O, you will not get \fBEAGAIN\fP.
Nonetheless Nonetheless
you should still cope with these errors for completeness. you should still cope with these errors for completeness.
.TP .TP
\fB8.\fP 8.
Never call Never call
.BR read (2), .BR read (2),
.BR recv (2), .BR recv (2),
@ -454,7 +454,7 @@ or
.BR send (2) .BR send (2)
with a buffer length of zero. with a buffer length of zero.
.TP .TP
\fB9.\fP 9.
If the functions If the functions
.BR read (2), .BR read (2),
.BR recv (2), .BR recv (2),
@ -471,14 +471,14 @@ In the above example,
I close the descriptor immediately, and then set it to \-1 I close the descriptor immediately, and then set it to \-1
to prevent it being included in a set. to prevent it being included in a set.
.TP .TP
\fB10.\fP 10.
The timeout value must be initialized with each new call to The timeout value must be initialized with each new call to
.BR select (), .BR select (),
since some operating systems modify the structure. since some operating systems modify the structure.
.BR pselect () .BR pselect ()
however does not modify its timeout structure. however does not modify its timeout structure.
.TP .TP
\fB11.\fP 11.
I have heard that the Windows socket layer does not cope with OOB data I have heard that the Windows socket layer does not cope with OOB data
properly. properly.
It also does not cope with It also does not cope with
@ -583,6 +583,7 @@ listen_socket(int listen_port)
struct sockaddr_in a; struct sockaddr_in a;
int s; int s;
int yes; int yes;
if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) { if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket"); perror("socket");
return \-1; return \-1;
@ -612,6 +613,7 @@ connect_socket(int connect_port, char *address)
{ {
struct sockaddr_in a; struct sockaddr_in a;
int s; int s;
if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) { if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket"); perror("socket");
close(s); close(s);

4
man2/semop.2
View File

@ -156,7 +156,7 @@ Otherwise
(the count of processes waiting until this semaphore's value becomes zero) (the count of processes waiting until this semaphore's value becomes zero)
is incremented by one and the process sleeps until is incremented by one and the process sleeps until
one of the following occurs: one of the following occurs:
.IP \(bu .IP \(bu 3
.I semval .I semval
becomes 0, at which time the value of becomes 0, at which time the value of
.I semzcnt .I semzcnt
@ -230,7 +230,7 @@ Otherwise
(the counter of processes waiting for this semaphore's value to increase) (the counter of processes waiting for this semaphore's value to increase)
is incremented by one and the process sleeps until is incremented by one and the process sleeps until
one of the following occurs: one of the following occurs:
.IP \(bu .IP \(bu 3
.I semval .I semval
becomes greater than or equal to the absolute value of becomes greater than or equal to the absolute value of
.IR sem_op , .IR sem_op ,