Bourne shell built-in commands

Special commands are built into the Bourne shell and run in the shell process.

Unless otherwise indicated, output is written to file descriptor 1 (standard output) and the exit status is 0 (zero) if the command does not contain any syntax errors. Input and output redirection is permitted.

The following special commands are treated somewhat differently from other special built-in commands:

: (colon)     exec            shift
. (dot)       exit            times
break         export          trap
continue      readonly        wait
eval          return

The Bourne shell processes these commands as follows:

Keyword parameter assignment lists preceding the command remain in effect when the command completes.
I/O redirections are processed after parameter assignments.
Errors in a shell script cause the script to stop processing.