April 2006 - openSUSE Programming - openSUSE Mailing Lists

The meaning of atomic in write()
by Verdi March 08 Apr '06

08 Apr '06

Hi, The open group specification says that write() is atomic as long as the number of bytes is not larger than PIPE_BUF. In the following program, sometimes only one process successfully writes to the file. I thought that fprintf also uses write() underneath, so the file should contains strings from both processes. Any insight? #include <stdio.h> #include <limits.h> #include <assert.h> int main() { int i; FILE *f; printf("bufsiz=%d pipe_buf=%d\n", BUFSIZ, PIPE_BUF); f = fopen( "test.txt" , "w" ); /* f = stdout; */ fprintf( f, "Parent is process %d\n", getpid() ); assert(fork() >= 0); for (i=1; i<4; i++) fprintf( f, " %8d: %d\n", getpid(), i ); fclose( f ); return 0; } Here are some results, the first correctly contains strings from both processes, but the second only contains strings from one process: cincai@verdimar:/tmp> ./a.out; cat haha.txt bufsiz=8192 pipe_buf=4096 Parent is process 25831 25832: 1 25832: 2 25832: 3 bufsiz=8192 pipe_buf=4096 Parent is process 25831 25831: 1 25831: 2 25831: 3 cincai@verdimar:/tmp> ./a.out ;cat haha.txt bufsiz=8192 pipe_buf=4096 Parent is process 25836 25837: 1 25837: 2 25837: 3 -- Bis zu 70% Ihrer Onlinekosten sparen: GMX SmartSurfer! Kostenlos downloaden: http://www.gmx.net/de/go/smartsurfer

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USB device access?
by Goran 08 Apr '06

08 Apr '06

Hello, I have a c-program for talking with a USB-device. Doing a lsusb command gives this result: # lsusb Bus 005 Device 001: ID 0000:0000 Bus 004 Device 001: ID 0000:0000 Bus 003 Device 002: ID 10cf:5500 Velleman Components, Inc. 8055 Experiment Interface Board (address=0) Bus 003 Device 001: ID 0000:0000 Bus 002 Device 001: ID 0000:0000 Bus 001 Device 003: ID 09da:001a A4 Tech Co., Ltd Wireless Mouse & RXM-15 Receiver Bus 001 Device 001: ID 0000:0000 The program works as long as I use it as root. How do I change my SuSE 9.3 setup to allow a user or a group to talk with this device? Thanks, Göran

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Re: WELCOME to suse-programming-e@suse.com
by Bhargavi 05 Apr '06

05 Apr '06

On Wednesday 05 April 2006 12:09, suse-programming-e-help(a)suse.com wrote: > Hi! This is the ezmlm program. I'm managing the > suse-programming-e(a)suse.com mailing list. > > I'm working for my owner, who can be reached > at suse-programming-e-owner(a)suse.com. > > Acknowledgment: I have added the address > > bhargavi_karanam(a)infosys.com > > to the suse-programming-e mailing list. > > Welcome to suse-programming-e(a)suse.com! > > Please save this message so that you know the address you are > subscribed under, in case you later want to unsubscribe or change your > subscription address. > > To unsubscribe, send a message to: > > <suse-programming-e-unsubscribe-bhargavi_karanam=infosys.com(a)suse.com> > > Q1. What is the suse-programming-e mailing list? > A1. A mailing devoted to programming and software development on > SuSE Linux. > > Q2. What is appropriate content for the list? > A2. Discussions about C, C++, scripting, etc. > > Q3. 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