brenns10 / lsh Goto Github PK

Hi,

If you run the command bash -ic <some_command> the shell gets stopped. Not sure why though, I'm running in the same issue with mine ;(

Hi! Is this project open to contribution?
He never contributes no projects in github, but he caught my attention, it would be a good challenge for me. If you want help, I'm at your disposal.

I did not know where else to raise an issue regarding the blog post, as getline is not there in the code on github.

The code on the blog post does not handle the case where the user inputs an EOF, wanting to exit the shell. I believe it should be:

char *lsh_read_line(void)
{
  char *line = NULL;
  ssize_t bufsize = 0;  // have getline allocate a buffer for us
  if (getline(&line, &bufsize, stdin) == -1)
    exit(EXIT_SUCCESS);
  return line;
}

Or, to be even more pedantic:

char *lsh_read_line(void)
{
  char *line = NULL;
  ssize_t bufsize = 0;  // have getline allocate a buffer for us

  if (getline(&line, &bufsize, stdin) == -1){
    if (feof(stdin)) {  
      exit(EXIT_SUCCESS);  // We recieved an EOF
    } else  {
      perror("readline");
      exit(EXIT_FAILURE);
    }
  }
  return line;
}

I really enjoyed reading this tutorial, I read it all in one go, tried to write the code, and it finally ran successfully.
But I have a small problem is that I did not find any code related to the two commands ls and pwd, but I can use them when launch the program, can you explain why?
Finally, thank you very much for writing this tutorial, it brought me a happy afternoon.

I compiled your shell against musl libc and then the ">" prompt is missing.

The fix is easy enough:

diff --git a/src/main.c b/src/main.c
index 39b8528..0a705eb 100644
--- a/src/main.c
+++ b/src/main.c
@@ -255,6 +255,7 @@ void lsh_loop(void)

do {
printf("> ");

• fflush(stdout);
  line = lsh_read_line();
  args = lsh_split_line(line);
  status = lsh_execute(args);

Why in child process, it exits with EXIT_FAILURE ?
if (execvp(args[0], args) == -1) { perror("lsh"); } exit(EXIT_FAILURE);

I think it should be:
_exit(EXIT_SUCCESS);

Hi :) I just wanted to contribute to your excellent tutorial by (I think) improving the error handling in lsh_read_line(). Unless I'm mistaken, I don't think it currently handles the case when EOF actually indicates a read error and not a "successful" EOF/an EOF proper. My own code for the while loop looks more or less like this at the moment (you can see I'm (a) checking for the meaning of the returned EOF and (b) ensuring the buffer is freed before exiting):

// rest of code

while (1) {
        c = getc(stdin);
        
        if (c == '\n') {
            rl_buf[pos] = '\0';
            return rl_buf;
        } else if (c == EOF && ferror(stdin)) {
            fprintf(stderr, "ERROR: read error (%d)\n", errno);
            free(rl_buf);
            exit(EXIT_FAILURE);
        } else if (c == EOF && feof(stdin)){
            free(rl_buf);
            exit(EXIT_SUCCESS);
        }

        rl_buf[pos] = c;
        pos++;
        
        // rest of code
}

What do you think? Have I made a mistake in my reasoning?

I modified user to use it bash shell
usermod -s "binary" username
it does not working, when i change back usermod -s /bin/bash username

it works

I really enjoyed testing your lsh and reading the blog post.

FYI & OFFTOPIC: I also created a simple Rust version for fun: https://gist.github.com/rubenrua/55b2ab6757b6c716f05595548784593a

Why is the last byte replaced with \0 on EOF?
This makes it impossible to exit the shell using ^D.
A simple fix would be:

if (c == EOF)
    exit(0);

I believe there is a slight mistake in implementation of realloc function in the main.c at line 182.
Instead of:
buffer = realloc(buffer, bufsize);
The code should have been:
buffer = realloc(buffer, bufsize * sizeof(char));