MPE/iX Shell and Utilities Reference Manual, Vol 2

sh(1) MPE/iX Shell and Utilities sh(1)

shell environment. The shell sets up a shell utility’s environment to include the following:

• open ﬁles, subject to redirection

• current working directory (see cd(1))

• ﬁle creation mask (see umask(1))

• traps; traps caught by the shell are set to default values and traps ignored by the shell are

ignored by the utility

• variables deﬁned inside the shell and having the export attribute

Built-in Commands

The following commands are built into the shell. Building such commands into the shell

increases the performance of shell scripts and allows access to the shell’s internal data struc-

ture and variables. For details on a command, see its man page. These internal commands

have semantics indistinguishable from external commands.

: . [ alias break

cd continue echo eval exec

exit export false fc getopts

let newgrp print pwd read

readonly return set shift test

time times trap type typeset

ulimit unmask unalias unset wait

whence

POSIX.2 recognizes a subset of these commands as special built-ins. Syntax errors in special

built-in commands cause a non-interactive shell to exit with the exit status set by the com-

mand. The special built-in utilities are:

: . break continue

eval exec exit export

readonly return set shift

trap typeset unset

As well as built-in commands, the shell has a set of predeﬁned aliases:

functions hash history integer

nohup r stop suspend

See alias(1) for details.

1-540 Commands and Utilities