问题
I'm trying to emulate a terminal using a C program in Linux and need my program to display a custom prompt while the program executes. Is there a way to display it using my C program? (I can always try to printf "My-prompt" every line manually, but I'm looking for a better way). Also I can't use any additional libraries other than the basic ones so GNU Readline library and editline library wouldn't work (as suggested in another thread). for example:
user@mypc:~$ ./a.out
my_custom_prompt>3+5
my_custom_prompt>8
my_custom_prompt>exit
user@mypc:~$
回答1:
In your example, you already have got a terminal. You want to write a command-line interface with a prompt, not a terminal.
I can always try to printf "My-prompt" every line manually, but I'm looking for a better way
There’s nothing wrong with this approach. You have a loop which prints the prompt and waits for input afterwards. As Kunerd said in the comment, one line of code.
Normally, a prompt is printed to stderr rather than stdout. This has the advantage, that the prompt appears before a newline is written, as stderr is unbuffered (and in combination with piping and redirection it seems reasonable to me, that this stuff doesn’t go to the same stream as the actual output).
Also I can't use any additional libraries other than the basic ones so GNU Readline library and Editline library wouldn't work
Doing this in a way strictly conforming to the C standard and not using any libraries but the standard one makes things like line editing (other than using backspace) or a command history (close to) impossible. If that’s OK for you, look for fgets etc. and keep in mind, that stdin is usually line-buffered.
POSIX specifies some additional properties of terminals, see e.g. http://pubs.opengroup.org/onlinepubs/9699919799/. Maybe curses is also of interest for you.
回答2:
I believe what the OP wants is to simply have the "prompt" printed along with any program output, without having to add this manually every time. There is a way to do this, if you write a wrapper function on top of printf to do this, and call that instead of printf directly. Probably this will help: http://www.ozzu.com/cpp-tutorials/tutorial-writing-custom-printf-wrapper-function-t89166.html
回答3:
Perhaps you're looking for fgets() documentation?
来源：https://stackoverflow.com/questions/25820420/how-to-display-a-custom-prompt-during-the-execution-of-c-program