CODEWITHSUNDEEP
clinuxpthreadsposixncurses
outofcaffeine
outofcaffeine

Reputation: 113

Writing and reading from terminal using pthreads

I want to create a multithreaded application in C using pthreads. I want to have a number of worker threads doing stuff in the background, but every once in a while, they will have to print something to the terminal so I suppose they will have to

Also, I want the user to be able to "reply" to the output. For the sake of simplicity, I'm going to assume that nothing new will be written to the terminal until the user gives an answer to a thread's output, so that new lines are only written after the user replies, etc. I have read up on waiting for user input on the terminal, and it seems that ncurses is the way to go for this.

However, now I have read that ncurses is not thread-safe, and I'm unsure how to proceed. I suppose I could wrap everything terminal-related with mutexes, but before I do that I'd like to know if there's a smarter and possibly more convenient way of going about this, maybe a solution with condition variables? I'm somewhat lost here, so any help is welcome.

Upvotes: 1

Views: 880

Answers (2)

0xhacker
0xhacker

Reputation: 1119

You can use fprintf on terminal. fprintf takes care of the concurrency issues, like it will use mutex locks on stdout before writing to the output device.

Upvotes: 0

David Schwartz
David Schwartz

Reputation: 182753

Why not just have a thread whose job is to interact with the terminal?

If other threads want to send message or get replies from the terminal, they can create a structure reflecting that request, acquire a mutex, and add that structure to a linked list if structures. The terminal thread will walk the linked list, outputting data as needed and getting replies as needed.

You can use a condition variable to signal the terminal thread that there's now data that needs to be output. The structure in the linked list can include a response condition variable that the terminal thread can signal when it has the reply, if any.

For output that gets no reply, the terminal thread can delete the structure after it outputs its contents. For output that gets a reply, the terminal thread can signal the thread that's interested in the output and then let that thread delete the structure once it has copied the output.

Upvotes: 1

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