nice—runs a command at low priority

nice [ –increment ] command [ arguments ]

/usr/bin/nice executes a command with a lower CPU scheduling priority. The invoking process (generally the user's shell) must be in the time-sharing scheduling class. The command is executed in the time-sharing class. An increment of 10 is the default. The increment value must be in a range between 1 and 19, unless you are the superuser. Also a csh built-in.