Hello everyone,

I'm trying to write a program in c++ for Linux and I want to receive data from other program's(wireless-tools) and also call other program's(wireless-tools).
Anyone got an idea how to do this?

Regards Bart.

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Hi,
I will not get into the C++ specific syntax, but will briefly explain the concepts of Interprocess communication.

Two porcess (i.e. programs) could talk to each other in the following ways:

1. Sockets
2. Pipes
3. Message queues

I guess you have to use one of the above to talk to another program.

To call another program, depends on how much flexibility you have in building the other program. If its totally yours, i suggest, you make it into a shared library and load it at run time.

For calling other processes from your process, i know of 3 ways.

1. Fork() and Exec()
Fork creates a child process from your process. So after the fork() you have two processes with you. (one child and one parent). Exec() just overlays the other process on top of your process. You might want to exec() on the child and keep the parent for monitoring purposes. (the decision is yours)

2. Exec() (no fork)
It just gets the new process on top of your process and you loose your process.

3. System()
It opens a shell and calls your program in that shell and exits. (it internally uses, fork() and exec())

My C++ knowledge is pretty limited and i am not sure of the calls or API that do the above in C++.

I have tried to briefly explain the concepts above and i hope it helps you.

thanks,
Viral

Thanks alot,
I found the system() command in the source code of a front-end program though. I use it now to call the other program and send the output to a file. After that I can read the file.

I don't know if this is a good way to do it, but it works.
sample(for future reference):

//declaration
int iTemp
QFile tmpFile;
QTextStream stream;

//put stats from iwlist in tmp-file
iTemp = system("iwlist eth1 scan > /tmp/iwlist");

//open tmp-file
tmpFile.setName("/tmp/wifiGui-iwlist");
tmpFile.open(IO_ReadOnly);
stream.setDevice(&tmpFile);

//here you can read the file/aka the output of iwlist

//close and remove it
tmpFile.close();
tmpFile.remove();
(uses Qt)

Yeah,
The code that you showed looks like it will work. But the more elegant way to do it would be...

(Again just the concepts..not the code from me ;-))

1. fopen() the file with the name and location that you want.

2. fwrite() whatever you want to write in it.

3. fread() it and do whatever you want.

Do it this way if you are really particular to do it the 'right' way..else whatever you have shown seems to be good enough.

Cheers,
Viral