sh-posix.1 (2010 09)

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sh-posix(1) sh-posix(1)

• Setting the value of SHELL,

ENV,orPATH

• Specifying path or command names containing

• Redirecting output (>, >|,

<>, and >>)

The restrictions above are enforced after the

.profile

and ENV ﬁles are interpreted.

When a command to be executed is found to be a shell procedure,

rsh invokes sh to execute it. Thus, the

end-user is provided with shell procedures accessible to the full power of the standard shell, while being

restricted to a limited menu of commands. This scheme assumes that the end-user does not have write

and execute permissions in the same directory.

These rules effectively give the writer of the

.profile ﬁle complete control over user actions, by per-

forming guaranteed set-up actions and leaving the user in an appropriate directory (probably not the

The system administrator often sets up a directory of commands (usually

/usr/rbin) that can be safely

invoked by

rsh. HP-UX systems provide a restricted editor

red (see ed(1)), suitable for restricted users.

Deﬁnitions

metacharacter One of the following characters:

;&()|<>newline space tab

blank A tab or a space.

identifier A sequence of letters, digits, or underscores starting with a letter or underscore.

Identiﬁers are used as names for functions and named parameters.

word A sequence of characters separated by one or more nonquoted metacharacters.

command A sequence of characters in the syntax of the shell language. The shell reads each

command and carries out the desired action, either directly or by invoking separate

utilities.

special command A command that is carried out by the shell without creating a separate process.

Except for documented side effects, most special commands can be implemented as

separate utilities.

# Comment delimiter. A word beginning with # and all following characters up to a

newline are ignored.

parameter An identiﬁer, a decimal number, or one of the characters

!, #

, $, *, -, ?, @, and _.

See the Parameter Substitution subsection.

named parameter A parameter that can be assigned a value. See the Parameter Substitution subsec-

tion.

variable A parameter.

environment variable

A parameter that is known outside the local shell, usually by means of the

export special command.

Commands

A command can be a simple command that executes an executable ﬁle, a special command that executes

within the shell, or a compound command that provides ﬂow of control for groups of simple, special, and

compound commands.

Simple Commands

A simple command is a sequence of blank-separated words that may be preceded by a parameter assign-

ment list. (See the Environment subsection). The ﬁrst word speciﬁes the name of the command to be exe-

cuted. Except as speciﬁed below, the remaining words are passed as arguments to the invoked command.

The command name is passed as argument

0 (see exec(2)). The value of a simple command is its exit

status if it terminates normally, or 128+errorstatus if it terminates abnormally (see signal (5) for a list of

errorstatus values).

A pipeline is a sequence of one or more commands separated by a bar (

|) and optionally preceded by an

exclamation mark (!). The standard output of each command but the last is connected by a pipe (see

pipe (2)) to the standard input of the next command. Each command is run as a separate process; the

shell waits for the last command to terminate. If ! does not precede the pipeline, the exit status of the

pipeline is the exit status of the last command in the pipeline. Otherwise, the exit status of the pipeline is

2 Hewlett-Packard Company − 2 − HP-UX 11i Version 3: September 2010