cbinchdirexecvegetcwd

Execve cd /bin pwd [C]

I am currently writing a shell in C (school project). My cd and pwd is working. But when I do: cd /bin and after pwd, pwd shows /usr/bin. For me it looks like execve with pwd can't handle /bin but why?

name% ./myshell
name: cd
Current working dir: /nfs/homes/name
name: cd /bin
Current working dir: /usr/bin
name: exit

Here I was working with getcwd(). But also when I pass pwd to Execve it is the same resulut. I fixed the problem.

But I want to know why this happens and are there other folders that are not working?

int ft_cd(char *path)
{
    if (!path)
        chdir(getenv("HOME"));
    else if (chdir(path))
        ft_printf("bash: cd: %s: No such file or directory\n", path);
    if (!ft_strcmp(path, "/bin") || !ft_strcmp(path, "/bin/"))
        return (1);
    return (0);
}

Now I am looking for cd /bin or cd /bin/. In this case, I print /bin when pwd is called. ft_strcmp is almost thesame as strcmp.

Solution

  • Run ls -l /bin and you will see it is a symlink to /usr/bin.

    Since your pwd code (presumably using getcwd()) doesn't know how you arrived in /usr/bin, it reports that name (the physical name for the directory) rather than /bin (the logical name).

    Look at the POSIX specification for the cd command, and you'll see the -L (logical) and -P (physical) options. Your command is effectively implementing the -P option (only). Also look at the POSIX specification for the pwd command; similar comments apply.