De acordo com Como fazer o Bash :
[21:58:33][giles@nikola:~]$ PS1="[\$(date +%H%M)][\u@\h:\w]\$ " [2159][giles@nikola:~]$ ls bin mail [2200][giles@nikola:~]$
It's important to notice the backslash before the dollar sign of the command substitution. Without it, the external command is executed exactly once: when the PS1 string is read into the environment.