Atomic lock file creation Post: 302276305

Sponsored Content

Top Forums Programming Atomic lock file creation Post 302276305 by lagigliaivan on Tuesday 13th of January 2009 12:26:50 PM

01-13-2009

Registered User

code

I think this could work. I extracted the comment from open function man page.

Code:

#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(void)
{
        int fd;

 /*           O_EXCL:

              If O_CREAT and O_EXCL are set, open() shall fail  if  the  file
              exists.  The  check  for the existence of the file and the cre-
              ation of the file if it does not exist  shall  be  atomic  with
              respect to other threads executing open() naming the same file-
              name in the same directory with  O_EXCL  and  O_CREAT  set.  If
              O_EXCL  and  O_CREAT  are  set, and path names a symbolic link,
              open() shall fail and set errno to [EEXIST], regardless of  the
              contents  of the symbolic link. If O_EXCL is set and O_CREAT is
              not set, the result is undefined.
*/


        if ( (fd = open("./test.txt", O_RDWR|O_CREAT|O_EXCL)) < 0 )
        {
                perror("open");
        }
        else
        {
                /*here you can use fcntl in order to lock the file*/
        }

        return 0;
}

lagigliaivan

View Public Profile for lagigliaivan

Find all posts by lagigliaivan

9 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

How to lock a file in unix?

We wish to keep a sequence number in a file. When someone wants to get the next sequence number we need to lock the file, get the next number and increment it by one. How do you do that? I know how to get the number and increment it but how do I lock the file and test that it is locked or not...

2. UNIX for Dummies Questions & Answers

lock file!

I found a lock file like this lrwxrwxr-x 1 sskb apollo 16 Oct 22 22:00 lock -> hostname:2747 (pl. note that hostname is a number like 123.4.5.6) but this was not shown in the file manager eventhough I had selected to show the hidden files. I could not even read the...

3. UNIX for Dummies Questions & Answers

how to lock keyboard without using lock command

how can I lock my keyboard while I'm away from the computer without using lock command. What other commands gives me the option to lock keyboard device? thanks

4. UNIX for Dummies Questions & Answers

Lock File

Hi, We have a lock file being created called lck8c0001 created in Unixware 2.1.2. This is locking a printer. According to some websites, 8c0001 relates to the device name. How does one link 8c0001 to those devices listed in the /dev folder? I have done a ps -lp for all printers and have...

5. UNIX for Advanced & Expert Users

file lock

I have an Essbase installation on Solaris 10 and need to get the backups configured. Unfortunately several key files are locked and Essbase (OLAP application) is not releasing the locks when the Essbase or the applications within stop running. It appears I can use chmod to unlock the files but I...

6. Red Hat

Security Question: Lock after invalid login, Session Lock and Required Minimum Password Length

Hello all, If anyone has time, I have a few questions: How do I do the following in Linux. We are using Red Hat and Oracle Enterprise Linux, which is based on Red Hat too. 1. How to lock the account after a few (like 3) invalid password attempts? 2. How do you lock a screen after 30...

7. UNIX for Advanced & Expert Users

Testing privileges -lock lockfile /var/lock/subsys/..- Permission denied

Hi all, I have to test some user priviliges. The goal is to be sure that an unauthorized user can't restart some modules (ssh, mysql etc...). I'm trying to automate it with a shell script but in same cases I got the syslog broadcast message. Is there any way to simply get a return code...

8. Shell Programming and Scripting

Lock file creation

Hi, Please let me know how these steps are creating a lock file using echo " ". LOCK_FILE=${LOG_DIR}/${DBNAME}_MD.lock # create lock file if then echo "Another process is running already. Will terminate this one." >> ${LOG_FILE} 2>&1 echo "If the lock file is not needed, please...

9. Shell Programming and Scripting

Help using Flock (file lock)

Hello, I have been working on using "flock"/file lock to prevent two instances of a bash script from being executed. Below is a simplified version of what I have to illustrate the flock part. It works as it is set up there below however the piece I am trying to figure out is how to get it to...

LEARN ABOUT DEBIAN

os_type

os_type(3alleg4)						  Allegro manual						  os_type(3alleg4)

NAME

       os_type - Stores the detected type of the OS. Allegro game programming library.

SYNOPSIS

       #include <allegro.h>

       extern int os_type;

DESCRIPTION

       Set by allegro_init() to one of the values:

	  OSTYPE_UNKNOWN    - unknown, or regular MSDOS
	  OSTYPE_WIN3	    - Windows 3.1 or earlier
	  OSTYPE_WIN95	    - Windows 95
	  OSTYPE_WIN98	    - Windows 98
	  OSTYPE_WINME	    - Windows ME
	  OSTYPE_WINNT	    - Windows NT
	  OSTYPE_WIN2000    - Windows 2000
	  OSTYPE_WINXP	    - Windows XP
	  OSTYPE_WIN2003    - Windows 2003
	  OSTYPE_WINVISTA   - Windows Vista
	  OSTYPE_OS2	    - OS/2
	  OSTYPE_WARP	    - OS/2 Warp 3
	  OSTYPE_DOSEMU     - Linux DOSEMU
	  OSTYPE_OPENDOS    - Caldera OpenDOS
	  OSTYPE_LINUX	    - Linux
	  OSTYPE_SUNOS	    - SunOS/Solaris
	  OSTYPE_FREEBSD    - FreeBSD
	  OSTYPE_NETBSD     - NetBSD
	  OSTYPE_IRIX	    - IRIX
	  OSTYPE_DARWIN     - Darwin
	  OSTYPE_QNX	    - QNX
	  OSTYPE_UNIX	    - Unknown Unix variant
	  OSTYPE_BEOS	    - BeOS
	  OSTYPE_MACOS	    - MacOS
	  OSTYPE_MACOSX     - MacOS X

SEE ALSO

       allegro_init(3alleg4), os_version(3alleg4), os_multitasking(3alleg4)

Allegro 							   version 4.4.2						  os_type(3alleg4)