Visit Our UNIX and Linux User Community


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


 
Thread Tools Search this Thread
Top Forums UNIX for Advanced & Expert Users Needs help in launching a console application with the help of daemon process
# 1  
Old 01-03-2011
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 console and try to read the command in while loop such as:
Code:
std::getline(std::cin, cmd); 
if(std::cin.fail()) 
{  
 //stop the reading and execution of application
}

In daemon program that launches the application as a child process, after forking and in child process, after setting sid and chdir, we close the descriptor like
Code:
close(STDOUT_FILENO);
close(STDERR_FILENO);

but does not closing the STDIN_FILENO so that the application can read the command from STDIN_FILENO. Daemon process does fork and execv the application so that application can run as a child of daemon process. On Linux, this daemon program for running the application as a child process is working fine. Daemon program runs the application successfully on Linux platform and runs as per the expectation.
But when running the daemon program from windows with the help of plink (for executing the daemon process on Linux platform from window), plink executes the daemon and the daemon process executes the application on Linux but just after 1-2 seconds, application and daemon both stop their execution and child of the application run as a daemon process. Except the child of application, rest all other process like main daemon program, application are stopping the execution. Could you please suggest me what is causing the problem and why from windows (with the help of plink) daemon process and the application is not running as expected on Linux.
Anyone with knowledge of how to get rid of these would be greatly appreciated.
Thanks

Last edited by vbe; 01-03-2011 at 01:12 PM.. Reason: code tags
# 2  
Old 01-03-2011
Perhaps the application is expecting there to be a stdout/stderr file descriptor - instead of the close you could try:
Code:
int fd=open("/dev/null",O_WRONLY);
if(fd >=0) {
    dup2(fd,STDOUT_FILENO);
    dup2(fd,STDERR_FILENO);
    close(fd);
}

Obviously on Linux you want to open "/dev/null", but I guess on windows that would be "nul"...
# 3  
Old 01-04-2011
Thanks for the suggestion, I have already tried this but fail to run the application on Linux machine with plink from windows machine.
As I explained above, there is no problem in running daemon and application (child of daemon) on Linux machine. Problem is there when I am trying to run the daemon on Linux machine from windows machine(remote machine) with plink. I mean on windows command prompt executing the following command:
plink -ssh -pw <password> <machine IP>:/ "path"; ./daemon

This command will establish the connection with Linux machine and will execute daemon process present in the given path. This command is launching the daemon process on Linux machine but after 1-2 sec, daemon is stopping the execution. I am not able to find out the reason that causing the problem
# 4  
Old 01-04-2011
Perhaps you could try using "strace", eg:
Code:
plink -ssh -pw <password> <machine IP>:/ "path"; strace -s 8192 -v -f -o /tmp/trace.log ./daemon

strace should give you an idea of what may be going wrong (logged into /tmp/trace.log)

Previous Thread | Next Thread
Test Your Knowledge in Computers #153
Difficulty: Easy
Novell sold their Unix business operations to Microsoft in 1995.
True or False?

7 More Discussions You Might Find Interesting

1. Programming

Daemon process

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 ? (4 Replies)
Discussion started by: sundaresh
4 Replies

2. UNIX for Advanced & Expert Users

Launching a process in remote machine

Hi all, Normally to launch a process in the remote machine I will use ssh to the machine and launch the process.I want to launch the remote machine process with out login into the machine . Is there any way. It may be any workaround method. Thanks in advance .:) (3 Replies)
Discussion started by: karthigayan
3 Replies

3. Programming

Show progress in console application

Hi all I have a program in C++ that I compiled on Ubuntu 9.0 and Centos 5, after I got it running on Windows. In this program, I show progress of a process using the following construct: i = 0; quantum = floor(total_iterations, 100); perc = 0; do { remain = fmod(i, quantum); ... (3 Replies)
Discussion started by: msaqib
3 Replies

4. Red Hat

Problem launching process as BG with &

After i launch the process as back ground, when I try to grab the shell by sending the enter, process is going to Stopped state. How do I successfully run the job in bg with &. Thanks in Advance (1 Reply)
Discussion started by: hansini
1 Replies

5. 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

6. 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

7. 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

Featured Tech Videos