How can I set the contents of my terminal's title bar?

If you have a terminal that understands xterm-compatible escape sequences, and you just want to set the title one time, you can use a function like this:

settitle() { printf '\e]2;%s\a' "$*"; }

If you want to set the title bar to the currently-running command line every time you type a command, then this solution approximates it:

trap 'printf "\e]2;%s\a" "$(HISTTIMEFORMAT='' history 1)" > /dev/tty' DEBUG

However, it leaves the command history number in place, and it doesn't trigger on explicit subshells like (cd foo && make).

Or to use just the name and arguments of the current simple command:

trap 'printf "\e]2;%s\a" "$BASH_COMMAND" > /dev/tty' DEBUG

For Posix-compliant shells which don't recognize '\e' as a character sequence to be interpreted as Escape, '\x1b' may be substituted instead.