Build-In Commands

• eval arg ... :
  Executes args as a line of shell script.
• exec command:
  Begins executing command under the same process
  ID as the current script and never returns.
  This is most often used for ``wrapper'' scripts,
  which exec the real program binary as its last line.
• local var =value:
  Assigns a value to a variable,visible only
  within the current function.
• pushd directory and popd:
  For jumping around in a stack of directories.
• printf format args ... :
  This is like the C printf function, useful
  for more complex formatting of output.
  See printf(3) (man 3 printf) for details.
• unset VAR :
  Deletes a variable or environment variable.
  unset -f func deletes a function.
• wait:
  wait Pauses until all background jobs have completed.
  wait PID pauses until background process with
  process ID of PID has exited and returns its exit code.