Try `type cd` and you will see it is a shell builtin. In bash at least you can see the help via `help cd`. See 1.4.1.7 here for how bash searches for commands:

Try `type cd` and you will see it is a shell builtin. In bash at least you can see the help via `help cd`. See 1.4.1.7 here for how bash searches for commands: http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_01_04.html#sect_01_04_01_07 http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_01_04...