Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Daemon process
Top Forums Programming Daemon process Post 302857293 by Don Cragun on Thursday 26th of September 2013 12:35:24 AM
Old 09-26-2013
Quote:
Originally Posted by sundaresh
I wish to make a process run in the background, but only one instance of it, and not many,
so when the program is loaded, it has to check whether another instance of the same
program is running and if so to exit. How do I do this ?
If your system supports the semget() and semop() calls that are included in one of the optional features in the POSIX standards, you can use semget() to get access to a semaphore with a key that is known to your daemon. After getting the semaphore ID you can use semop() with an array of two operations at the start of your program. These operations are:
Code:
sem_num   sem_op   sem_flg
=======   ======   =======
   0         0     IPC_NOWAIT
   0         1     SEM_UNDO

If the semop() call fails with EAGAIN, another daemon is already running and owns the semaphore. If the semop() call succeeds, this daemon owns the semaphore until it terminates. (It doesn't matter if this daemon terminates due to receipt of an uncaught signal or terminates normally by calling exit, the SEM_UNDO flag will release ownership of the semaphore when the daemon terminates.)

If you don't have access to a similar set of semaphore operations, a common approach is to atomically create (with open flags O_CREAT | O_EXCL) a lock file and write the PID of the daemon that created the lock into the lock file. The daemon should then remove the lock file before it exits. (If the daemon is killed before it can remove the lock file, another daemon won't be able to start until you manually remove the lock file.)
This User Gave Thanks to Don Cragun For This Post:
sundaresh
 

10 More Discussions You Might Find Interesting

1. Programming

Daemon process

Hi, I have to write a daemon process, which performs certain operations in the background. Now since it performs operations in the background, it should not display anything to the standard output. The problem is that it still displays, text on standard output. Can anyone tell me (it is... (2 Replies)
Discussion started by: s_chordia
2 Replies

2. Programming

What is a daemon process?

This is gonna seem really silly to almost evryone here - but I need to know : what is a daemon process? Thanks (6 Replies)
Discussion started by: Kanu77
6 Replies

3. UNIX for Advanced & Expert Users

zombie daemon process!!

My daemon process is the child of init and init has the responsibility to remove it, once it turns zombie. But I want to ask why the daemon process which is child of init turns zombie in the first place. What measures I have to take to avoid this? rish (1 Reply)
Discussion started by: rish2005
1 Replies

4. Linux

daemon process

how i will write the daemon process,if any body have sample daemon process send me. (1 Reply)
Discussion started by: suresh_rupineni
1 Replies

5. Shell Programming and Scripting

How to starting process as daemon using ssh command?

Hello, I need to run a command on remote Linux using the ssh command from my local machine. I am able to execute the command on remote machine using ssh but it's behaving strangely. The command is supposed to start a daemon process on remote linux box and the control should return back to me... (5 Replies)
Discussion started by: nitinshukla
5 Replies

6. UNIX for Dummies Questions & Answers

How to write Pro*C daemon process using multithreading?

Hello, I am new to this forum and this is my first post here... I have never worked on either Pro*C or Multithreading..Now, i have to write a Pro*C, Multithreading daemon process.. I dont know where to start.. Can anybody help me with examples? 1. need to write a Pro*C multithreading... (0 Replies)
Discussion started by: kachiraju
0 Replies

7. Programming

How to find if a process a daemon ?

I have a scenario where I need to find if a process is a daemon process or not. This check needs to be done from within the process. I know there are no direct API's to do so. I have explored these options. 1. ctermid() - this can be unsuccessful as per the man pages 2. int devtty; if ((devtty... (7 Replies)
Discussion started by: vino
7 Replies

8. Shell Programming and Scripting

Diff between Bg and daemon process

Dear Unix Gurus, Plz provide major diff between background process and daemon process. Is it control available for daemon process?. (3 Replies)
Discussion started by: kkl
3 Replies

9. UNIX for Advanced & Expert Users

Needs help in launching a console application with the help of daemon process

Hi All, I am facing problem in launching a application with the help of a daemon process. Actually the application is based on command line that reads various commands for controlling the application from the console and accordingly executes those commands. The application always interact with... (3 Replies)
Discussion started by: gopallinux
3 Replies

10. Shell Programming and Scripting

run this script as a daemon process

Hi, HI , I have a simple script that moves files from one folder to another folder, I have already done the open-ssh server settings and the script is working fine and is able to transfer the files from one folder to another but right now I myself execute this script by using my creditianls to... (3 Replies)
Discussion started by: nks342
3 Replies

LEARN ABOUT SUSE

ncftpbatch

ncftpbatch(1)						      General Commands Manual						     ncftpbatch(1)

NAME

       ncftpbatch - Individual batch FTP job processor

SYNOPSIS

       ncftpbatch -d

       ncftpbatch -l

       ncftpbatch -D

OPTIONS

   Command line flags:
       -d      Begin  background  processing  of FTP jobs in the current user's $HOME/.ncftp/spool directory.  This returns immediately, because a
	       daemon process is spawned and ran in the background.

       -l      Lists the contents of the user's job queue.

       -D      This is like -d, except that the process does not become a daemon.

DESCRIPTION

       This program is responsible for processing background FTP requests.  It is normally only run by ncftp and not manually by  a  human  being,
       however you can run it to manually process the FTP job queue.

       The  jobs are spool files written to a user's $HOME/.ncftp/spool directory and have a special format and file-naming convention (which con-
       tains when the job is to be run).  ncftp runs this program when it needs to, but if the ncftpbatch daemon dies unexpectedly the	jobs  that
       are left in the queue will not be processed until another instance of ncftpbatch is run.

       ncftpget  and  ncftpput can also be used to submit jobs for batch processing, using those utilities' -b command-line flag.  If desired, you
       can also manually create the spool files although this procedure is not documented here (see the manual	page  for  ncftpspooler  for  more
       information on how to do that).

DIAGNOSTICS

       ncftpbatch  writes  to its own log file, the $HOME/.ncftp/spool/log file.  This file should be examined to determine if any ncftpbatch pro-
       cesses are actively working on jobs.

AUTHOR

       Mike Gleason, NcFTP Software (http://www.ncftp.com).

SEE ALSO

       ncftp(1), ncftpput(1), ncftpget(1).

ncftpbatch							  NcFTP Software						     ncftpbatch(1)
All times are GMT -4. The time now is 09:00 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy