using only one pipe for n processes (C programming)

hellraiserx9 · 03-21-2021, 06:51 PM

I'm confused on how can i use only one pipe for connecting n processes.

rtmistler · 03-21-2021, 07:44 PM

Quote:

Originally Posted by hellraiserx9

I'm confused on how can i use only one pipe for connecting n processes.

Welcome to the forums,

When you fork, you can continue to use the same handles, a.k.a. pipe.

Please consider reading a very old blog I wrote describing how to use pipes.

Using PIPES For Interprocess Communications

Otherwise suggest some general research or explanation as to what you do have in mind.

hellraiserx9 · 03-21-2021, 08:45 PM

/deleted

hellraiserx9 · 03-21-2021, 08:46 PM

Quote:

Originally Posted by rtmistler

Welcome to the forums,

When you fork, you can continue to use the same handles, a.k.a. pipe.

Please consider reading a very old blog I wrote describing how to use pipes.

Using PIPES For Interprocess Communications

Otherwise suggest some general research or explanation as to what you do have in mind.

Please see my code and tell me if there's any errors.

astrogeek · 03-21-2021, 09:51 PM

Welcome to LQ and the Programming forum!

Please wrap your code and data snippets inside [CODE]...[/CODE] tags. Doing so will preserve indentation and provide other visual clues which make it easier for others to comprehend. You may write those yourself as shown, or use the # button available with Advanced edit options. (A complete list of BBCode tags is always available via a link near the bottom of every thread view).

Although everyone here is willing to help, it is generally preferred that you attempt to understand your problems first, then ask for specific help when you get stuck, providing any error messages you cannot resolve along a short description of what you have done so far to try to understand and fix it.

Asking others to evaluate and debug code without further explanation may not attract the most helpful answers.

That said, the blog post linked by rtmistler looks like an excellent place to start, and one I had not previously seen!

Again, welcome to LQ, and good luck!

pan64 · 03-22-2021, 02:22 AM

Quote:

Originally Posted by hellraiserx9

... I have to do this using only one pipe. ...

Code:

const size_t cmds_count = argc - 1;

// creating pipes
int fd_pair[2];

for (size_t i = 0; i < cmds_count - 1; i ++)
    pipe(fd_pair);

that is altogether N calls to the function pipe

Otherwise yes, please use code tags to make your post readable.

Is this your homework? Where is this code coming from? Did you try to test it somehow?

hellraiserx9 · 03-22-2021, 02:49 AM

/deleted

pan64 · 03-22-2021, 03:13 AM

I don't understand this code (better to say I don't think it can work), but probably you can explain...

hellraiserx9 · 03-22-2021, 03:57 AM

Ofcourse. I can, i have a process and splitting the process into child again and again for until it becomes n processes using fork and then using pipe to connect every process using only one pipe

pan64 · 03-22-2021, 04:34 AM

but why do you think this common pipe will do what you want?

NevemTeve · 03-22-2021, 05:17 AM

@OP Could you please quote verbatim the text of your homework?

rtmistler · 03-22-2021, 06:21 AM

Have you used a debugger to follow the first process to confirm it does what you want, and the done the same with child #1?

How about have you printed out the pipe handles and/or the addresses of the descriptors, along with doing same for all the pids?

All of you've done is to ask a question for people to do that effort for you and provide you with the answer.

The code looks reasonable, not sure you need the dup's or to close descriptors unless you're making them all daemons. If it were me, I'd avoid any complications and use either debug method described above, but since they're there, then confirm they work properly, again using debug methods.

hellraiserx9 · 03-22-2021, 08:05 AM

Can someone suggest me some good article on pipes and forks?

rtmistler · 03-22-2021, 08:53 AM

Quote:

Originally Posted by hellraiserx9

Can someone suggest me some good article on pipes and forks?

Apologies but we're not any more adept at searching the web than you.

Please review this link for further information.

EDIT: (wrong thread edit addition - removed)

GazL · 03-22-2021, 09:30 AM

Beej's guide to IPC is my goto