Sponsored Content
Top Forums Programming behaviour of read() and write() after a select() Post 302245151 by ramen_noodle on Thursday 9th of October 2008 12:47:29 PM
Old 10-09-2008
Hello,

Quote:
Its just that I realized now, that neither select() nor O_NONBLOCK ("standard to *nix for alleviating blocking behaviors") work for ordinary files (I mean, who would have thought?)
This is one of the well known *nix gotchas.
Most unix systems programmers have gotten used to it.
Not that it's ideal.

Quote:
By the way, as long as you don't use ordinary files, O_NONBLOCK is not needed. select() does it's job very well even without O_NONBLOCK. On the other hand, if you use select(), O_NONBLOCK is not really needed anymore. Read man select_tut(2) on this.
"
Read or write not blocking on a resource after select returns is not entirely reliable at all times. The select_tut example is it's own best argument against using the non-blocking model imho. Also see: http://cr.yp.to/unix/nonblock.html

Quote:
You mean I'm trying to optimize too soon? I don't think so, because in this case I try to figure out a good overall structure for the app. This is better done before I write the bulk of code
You are ,imo, optimizing too soon and encountering problems that research may have
ameliorated. Please see if you haven't already: The C10K problem
 

10 More Discussions You Might Find Interesting

1. Programming

select() and read()

Hi, Could you please tell me how can I know which position a given read descriptor ocuppies in the descriptors table. I know that, for instance, 'stdin' ocuppies position ... what about the others descriptors that I create usings pipes or sockets?? Thanks! P.S.: Sorry for my bad English (2 Replies)
Discussion started by: jnuno
2 Replies

2. Programming

popening for read and write

How can 'popen()' be used for reading and writing to opening pipe? If i try 'popen("prog", "rw")' and then put and get chars - it does not work. What is wrong? (1 Reply)
Discussion started by: szzz
1 Replies

3. Shell Programming and Scripting

read and write from a file

I have tried to show the file name whose size is greater than 200 byte in current directory. Please help me. ls -l | tr -s " " " " | cut -f 5,9 -d " " >out.txt #set -a x `cat out.txt` i=0 `cat out.txt` | while do read x echo $x #re=200 j=0 if }" < "200" ] then echo $j j=`expr $j... (2 Replies)
Discussion started by: rinku
2 Replies

4. UNIX Desktop Questions & Answers

Wall, Write, select users, pipe a text file, HELP Before I'm Bald!

OK... I'm fairly new to unix having the admin handed to me on a platter w/almost no training. However, being a programmer, I do pick up things fairly easily, but this one is getting the best of me. I have a unix server that runs multiple versions of the same ERP system, hand crafted for our... (1 Reply)
Discussion started by: chimodel
1 Replies

5. Shell Programming and Scripting

Find all files with group read OR group write OR user write permission

I need to find all the files that have group Read or Write permission or files that have user write permission. This is what I have so far: find . -exec ls -l {} \; | awk '/-...rw..w./ {print $1 " " $3 " " $4 " " $9}' It shows me all files where group read = true, group write = true... (5 Replies)
Discussion started by: shunter63
5 Replies

6. IP Networking

read/write,write/write lock with smbclient fails

Hi, We have smb client running on two of the linux boxes and smb server on another linux system. During a backup operation which uses smb, read of a file was allowed while write to the same file was going on.Also simultaneous writes to the same file were allowed.Following are the settings in the... (1 Reply)
Discussion started by: swatidas11
1 Replies

7. IP Networking

write() / read() syntax

hi am newbie to unix and socket programing I am trying to figuring out syntax for read and write to send data from server to client and client can read it I have to send two integers write(newsockfd,buffer,"%d %d",x,y,0) writing from client where x and y are two integers.. ... (7 Replies)
Discussion started by: karthik1238
7 Replies

8. Shell Programming and Scripting

Read and write in the file

Hello Guys, How all are doing? I have an issue in Unix and want help from all of you I have a file in UNIX which it read by line by line , If at the end of line '0' is written the it should fetch that line into another file and change '0' to '1' and If at the end of line '1' is written then it... (10 Replies)
Discussion started by: adisky123
10 Replies

9. Programming

FIFO write and read

Can someone help me to write this program in C in QNX? Using the FIFO queues write a simple communication system consisting of programs write and read. The program write the parameters given strings enclosed in single quotes. These strings are written to the FIFO file. Reads the program read... (1 Reply)
Discussion started by: ebasse2
1 Replies

10. Shell Programming and Scripting

Bash to select oldest folder in directory and write to log

In the bash below the oldest folder in a directory is selected. If there are 3folders in the directory /home/cmccabe/Desktop/NGS/test and nothing is done to them (ie. no files deleted, renamed) then the bash correctly identifies f1 as the oldest. However, if something is done to the folder then... (4 Replies)
Discussion started by: cmccabe
4 Replies
uri_urn(3tcl)					    Tcl Uniform Resource Identifier Management					     uri_urn(3tcl)

__________________________________________________________________________________________________________________________________________________

NAME
uri_urn - URI utilities, URN scheme SYNOPSIS
package require Tcl 8.2 package require uri::urn ?1.1.2? uri::urn::quote url uri::urn::unquote url _________________________________________________________________ DESCRIPTION
This package provides two commands to quote and unquote the disallowed characters for url using the urn scheme, registers the scheme with the package uri, and provides internal helpers which will be automatically used by the commands uri::split and uri::join of package uri to handle urls using the urn scheme. COMMANDS
uri::urn::quote url This command quotes the characters disallowed by the urn scheme (per RFC 2141 sec2.2) in the url and returns the modified url as its result. uri::urn::unquote url This commands performs the reverse of ::uri::urn::quote. It takes an urn url, removes the quoting from all disallowed characters, and returns the modified urls as its result. BUGS, IDEAS, FEEDBACK This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category uri of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for enhancements you may have for either package and/or documentation. KEYWORDS
rfc 2141, uri, url, urn CATEGORY
Networking uri 1.1.2 uri_urn(3tcl)
All times are GMT -4. The time now is 07:21 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy