Subshells

The shell is just a program. It's not wired into the kernel. Many programmers who've been in the business for a while have written a shell, for their own amusement. If you haven't, you can imagine the pseudocode.

while (1) {
    put up a prompt
    read the line the user types in
    parse the line
    execute any commands you find
}

Thinking of the shell as just another program, no different from ls or date or cc, is a big help in dealing with the shell.

This week, I'll explore that a little.