I am running screen on a debian machine. To start a program with screen I run "screen -A -m -d -S sessionname command".

To send a command to a detached screen I use "screen -S sessionname -X stuff command".

However, this command only works if I have run "screen -x sessionname" first. I am making a c++ script to interact with a screen session, but it is a problem that I have to run "screen -x sessionname" first. Does anyone have a solution for my problem?

Yes, that is a known problem/bug. Several work-arounds have been reported on the screen-users maiing list. I have no idea whether it will ever be fixed.
--- rod.

Thx for the answer. I tried to make a system() call to a screen -x sessionname redirecting the output to /dev/null, but it didn't work. I found out that I could send the screen -x sessionname command to another (temporarily) screen session, but that didn't work neither (see below). I think it didn't happen fast enough, because if I run the script twice it will successfully send the command to the session "sessionname". Does anybody have a workaround that actually works?

Btw sorry for my bad english

My "workaround" that didn't work....

system ("screen -A -m -d -S temp screen -x sessionname");
system ("screen -S sessionname -X stuff 'command'");

Why do you need to send commands to a screen session that has never been in an attached state? If the answer is that it must be started at boot time, when there are no consoles to host your screen session, then perhaps my work-around can be of some use.
I start screen in an xterm that is hosted in an X virtual framebuffer, using xvfb. This allows me to start the screen session in an attached mode (in fact, it never has to become detached), allowing me to send commands to it arbitrarily. I can attach to it at any time from another 'real' xterm or from any other type of console. In the application it is used in at my site, it runs in multi-user mode, so others can also attach to the session. I launch this whole mess from /etc/rc.local
--- rod.

my problem might be similar. I am creating (or rather was until i saw this problem) a webpage for me which i can control my server. I normally go into the server via ssh and i do everything right there BUT i will be sharing my access control with several friends that are helping me out on the server. Some of the things i do in ssh involve the screen sessions like closing screens, reopening screens, sending messages to screens, etc..

What i want to do is this:

1. From my PC, in the homepage, execute an option that closes the screen and sends a message before closing. Something like:

ssh cyrex@server.com 'screen -S world -X "Closing in about 5 minutes"'

The problem is that when sending the messange to world it does not work. It does not get recieved. Any thoughts on this.

I think this is at least a little closer:
This will work if cyrex is the owner of the screen session, or if screen is running in multi-user mode. You probably also want to close off the stuffed message with a newline.
--- rod.

I have found a way to make it work with the help of previous messages:

I just use the solution of ThaHabbis with a delay (sleep 1) to enable the creation of the temporary screen (you may make a proper script witch detect if the temp screen is correctly created before or increase the delay if you have high load on server) and the echo of a newline to validate command to the screen prompt.

I am new here, impressive from the suggestions given by the guests.

This works for me:

screen -S <session-name> -p 0 -X stuff command

The key there is the -p 0 part. It selectes the window in which to write the command. If you don't specify it, it doesn't work unless you have already connected to the screen session.