Intro(C)

Intro -- introduces UNIX commands

Syntax

Unless otherwise noted, commands described in the ``Syntax'' section of a manual page accept options and other arguments according to the following syntax and should be interpreted as explained below.

name [-option ... ] [cmdarg ... ]

where:

[ ]

Surrounds an option or cmdarg that is not mandatory.

...

Indicates multiple occurrences of the option or cmdarg.

name

The name of an executable file.

option

This is always preceded by a ``-'' and may be in one of the two following forms:

noargletter: A single letter representing an option without an option-argument. Note that more than one noargletter option can be grouped after one ``-'' (Rule 5 in the following text).
argletter: A single letter representing an option requiring an option-argument.

optarg

An option-argument (character string) satisfying a preceding argletter. Note that groups of optargs following an argletter[ must be separated by commas or separated by white space and quoted (Rule 8 below).

cmdarg

Pathname (or other command argument) not beginning with ``-'', or ``-'' by itself indicating the standard input.

Command syntax standard: rules

These command syntax rules are not followed by all current commands, but all new commands use them. getopts(C) should be used by all shell procedures to parse positional parameters and to check for legal options. It supports rules 3-10 below. The enforcement of the other rules must be done by the command itself.

Command names (name above) must be between two and nine characters long.
Command names must include only lowercase letters and digits.
Option names (option above) must be one character long.
All options must be preceded by ``-''.
Options with no arguments may be grouped after a single ``-''.
The first option-argument (optarg above) following an option must be preceded by white space.
Option-arguments cannot be optional.
Groups of option-arguments following an option must either be separated by commas or separated by white space and quoted (for example, -o xxx,z,yy or -o "xxx z yy").
All options must precede operands (cmdarg above) on the command line.
``--'' may be used to indicate the end of the options.
The order of the options relative to one another should not matter.
The relative order of the operands (cmdarg above) may affect their significance in ways determined by the command with which they appear.
``-'' preceded and followed by white space should only be used to mean standard input.

Description

This section describes the use of the individual commands available in the UNIX Operating System. Each command in this section is labeled with a C (Command) for easy reference from other volumes. (Commands labeled with the letters ``CP'' (Programming commands) are documented as part of the Development System. The Development System is an optional supplemental package to the standard Operating System.)

For example, date(C) indicates a reference to a discussion of the date command in the C section; cc(CP) indicates a reference to a discussion of the cc command in the Development System.

The ``ADM'' (Administration) section contains descriptions of the commands used to maintain and administer the operating system. Other reference sections include the ``M'' (Miscellaneous) section, the ``S'' (System services) section, the ``HW'' (Hardware) section, and the ``F'' (File format) section.

Exit values

Upon termination, a command exits and returns a value to the calling shell. This exit value is used within shell scripts to determine whether the command completed successfully.

A command normally returns 0 (zero) for normal termination with no error; a non-zero exit value indicates problems such as incorrect parameters, and bad or missing data.

An exit value may sometimes be referred to as ``exit code'', ``exit status,'' or ``return value.'' Exit values are described only where special conventions are involved.

Diagnostics

This section describes the likely cause of error or information messages that may be output by a command. This section does not document system service messages which arise because of the failure of an underlying system call (see messages(M) for details of system service messages).

Warning

This section warns of the possible adverse consequences of using the command if certain precautions are not taken. These consequences may include loss of data, extended system down time, degradation of system performance, or damage to hardware.

Limitations

This section details aspects of usage, or limits of applicability of a command that a user should note. There may be reasons in the software or hardware why a command will fail in certain circumstances. These reasons may include internal limits on table size or number of temporary variables.

Authorization

This section documents if a command, normally only usable by the root user, may be invoked by trusted users if this is allowed by the authorize(F) file.