[SOLVED] Writing a shell program in C. How to EXIT?

krapykreme · 02-12-2016, 09:27 PM

Hello, I am implementing the exit function in my custom shell program. When I input exit however, it does not return to the initial command terminal. I would really appreciate if anyone can tell me what I am doing wrong. Here is my code:

Code:

if(strcmp(args[0], "exit") == 0){ 
        printf("Bye\n");
        exit(0);
    }

Michael Uplawski · 02-13-2016, 12:52 AM

Quote:

Originally Posted by krapykreme

Hello, I am implementing the exit function in my custom shell program. When I input exit however, it does not return to the initial command terminal.

What is happening, instead?

krapykreme · 02-13-2016, 01:19 AM

Quote:

Originally Posted by Michael Uplawski

What is happening, instead?

It is just showing the command prompt, instead of exiting to the terminal prompt. But I think I have figure out why. I think it is because when I input a command like "cd" or "pwd", the position at args[0] stores it, and is not overwritten by exit. I need to figure a way to to overwrite it.

Sorry if I am not clearly communicating.

Michael Uplawski · 02-13-2016, 01:26 AM

Quote:

Originally Posted by krapykreme

It is just showing the command prompt, instead of exiting to the terminal prompt. But I think I have figure out why. I think it is because when I input a command like "cd" or "pwd", the position at args[0] stores it, and is not overwritten by exit. I need to figure a way to to overwrite it.

Sorry if I am not clearly communicating.

Do not worry. But you provided a missing piece of information, in deed. ;-)
Have you seen the manpage on exit (man 3 exit)? I am not in your project, but feel that there is some nice hint for you in the documentation for the command. You may need to “prepare” the call to exit in a way that will permit the termination of the program in the way you want.

krapykreme · 02-13-2016, 03:05 AM

It works! Thanks

BW-userx · 02-13-2016, 09:51 AM

these two terms are euphemisms

Quote:

it is just showing the command prompt, instead of exiting to the terminal prompt.

a command prompt is within the terminal, hense it can be called a terminal prompt. so thats confusing me.

but, this is how I exit my scripts (for the most part)

Code:

if [[ -z "$DIRNAME" ]] ; then
echo "DIRNAME "$DIRNAME" is empty Yo"
exit 1
fi

it kicks it out of the script and leaves me at the command prompt in the trerminal I'm using.

BW-userx · 02-13-2016, 10:00 AM

Quote:

Originally Posted by krapykreme

It is just showing the command prompt, instead of exiting to the terminal prompt. But I think I have figure out why. I think it is because when I input a command like "cd" or "pwd", the position at args[0] stores it, and is not overwritten by exit. I need to figure a way to to overwrite it.

Sorry if I am not clearly communicating.

before calling exit, reset it to where ever or whatever this terminal prompt is then call exit?

Code:

if(strcmp(args[0], "exit") == 0){ 
        printf("Bye\n");

        working_dir="/path/to/wherever"

        exit(0);
    }

just an idea.

BW-userx · 02-13-2016, 10:07 AM

Quote:

Originally Posted by krapykreme

It works! Thanks

dang I missed this post,
plubish how you did it, then make solved. ples

Michael Uplawski · 02-13-2016, 01:35 PM

Quote:

Originally Posted by BW-userx

these two terms are euphemisms
a command prompt is within the terminal, hense it can be called a terminal prompt. so thats confusing me.

:-)) When krapykreme writes about her/his “custom shell program” you should just read “shell”, i.e. a kind of replacement for bash, dash and the like, probably with custom behaviour and not “full-featured”. It renders the exit() in deed quite interesting, though not overly complicated.

But I wondered in the same way, at first.

krapykreme · 03-10-2016, 06:04 PM

[QUOTE=BW-userx;5499606]Sorry, I am still learning the ways of the forum. Thanks for your help.

hydrurga · 03-10-2016, 06:13 PM

This has been a gripping thread, but I still have no idea what OP did to solve the problem. Can anyone enlighten me please?

jpollard · 03-11-2016, 06:21 AM

Quote:

Originally Posted by BW-userx

before calling exit, reset it to where ever or whatever this terminal prompt is then call exit?

Code:

if(strcmp(args[0], "exit") == 0){ 
        printf("Bye\n");

        working_dir="/path/to/wherever"

        exit(0);
    }

just an idea.

no need. The working directory of the parent process id cannot be affected by the child process.