Merge branch 'dmverity_options' of https://github.com/bluca/util-linux

[thirdparty/util-linux.git] / misc-utils / getopt.1

.TH GETOPT "1" "December 2014" "util-linux" "User Commands"
.SH NAME
getopt \- parse command options (enhanced)
.SH SYNOPSIS
.B getopt
.I optstring parameters
.br
.B getopt
[options]
.RB [ \-\- ]
.I optstring parameters
.br
.B getopt
[options]
.BR \-o | \-\-options
.I optstring
[options]
.RB [ \-\- ]
.I parameters
.SH DESCRIPTION
.B getopt
is used to break up
.RI ( parse )
options in command lines for easy parsing by shell procedures, and to
check for valid options.  It uses the
.SM GNU
.BR getopt (3)
routines to do this.
.PP
The parameters
.B getopt
is called with can be divided into two parts: options which modify
the way
.B getopt
will do the parsing
.RI "(the " options
and the
.I optstring
in the
.BR SYNOPSIS ),
and the parameters which are to be parsed
.RI ( parameters
in the
.BR SYNOPSIS ).
The second part will start at the first non\-option parameter that is
not an option argument, or after the first occurrence of
.RB ' \-\- '.
If no
.RB ' \-o '
or
.RB ' \-\-options '
option is found in the first part, the first parameter of the second
part is used as the short options string.
.PP
If the environment variable
.B GETOPT_COMPATIBLE
is set, or if the first
.I parameter
is not an option (does not start with a
.RB ' \- ',
the first format in the
.BR SYNOPSIS ),
.B getopt
will generate output that is compatible with that of other versions of
.BR getopt (1).
It will still do parameter shuffling and recognize optional arguments
(see section
.B COMPATIBILITY
for more information).
.PP
Traditional implementations of
.BR getopt (1)
are unable to cope with whitespace and other (shell-specific)
special characters in arguments and non\-option parameters.  To solve
this problem, this implementation can generate quoted output which
must once again be interpreted by the shell (usually by using the
.B eval
command).  This has the effect of preserving those characters, but
you must call
.B getopt
in a way that is no longer compatible with other versions (the second
or third format in the
.BR SYNOPSIS ).
To determine whether this enhanced version of
.BR getopt (1)
is installed, a special test option
.RB ( \-T )
can be used.
.SH OPTIONS
.TP
.BR \-a , " \-\-alternative"
Allow long options to start with a single
.RB ' \- '.
.TP
.BR \-h , " \-\-help"
Display help text and exit.  No other output is generated.
.TP
.BR \-l , " \-\-longoptions \fIlongopts\fP"
The long (multi\-character) options to be recognized.  More than one
option name may be specified at once, by separating the names with
commas.  This option may be given more than once, the
.I longopts
are cumulative.  Each long option name in
.I longopts
may be followed by one colon to indicate it has a required argument,
and by two colons to indicate it has an optional argument.
.TP
.BR \-n , " \-\-name \fIprogname\fP"
The name that will be used by the
.BR getopt (3)
routines when it reports errors.  Note that errors of
.BR getopt (1)
are still reported as coming from getopt.
.TP
.BR \-o , " \-\-options \fIshortopts\fP"
The short (one\-character) options to be recognized.  If this option
is not found, the first parameter of
.B getopt
that does not start with a
.RB ' \- '
(and is not an option argument) is used as the short options string.
Each short option character in
.I shortopts
may be followed by one colon to indicate it has a required argument,
and by two colons to indicate it has an optional argument.  The first
character of shortopts may be
.RB ' + '
or
.RB ' \- '
to influence the way options are parsed and output is generated (see
section
.B SCANNING MODES
for details).
.TP
.BR \-q , " \-\-quiet"
Disable error reporting by getopt(3).
.TP
.BR  \-Q , " \-\-quiet\-output"
Do not generate normal output.  Errors are still reported by
.BR getopt (3),
unless you also use
.BR \-q .
.TP
.BR \-s , " \-\-shell \fIshell\fP"
Set quoting conventions to those of
.IR shell .
If the \fB\-s\fR option is not given, the
.SM BASH
conventions are used.  Valid arguments are currently
.RB ' sh '
.RB ' bash ',
.RB ' csh ',
and
.RB ' tcsh '.
.TP
.BR \-T , " \-\-test"
Test if your
.BR getopt (1)
is this enhanced version or an old version.  This generates no
output, and sets the error status to 4.  Other implementations of
.BR getopt (1),
and this version if the environment variable
.B GETOPT_COMPATIBLE
is set, will return
.RB ' \-\- '
and error status 0.
.TP
.BR \-u , " \-\-unquoted"
Do not quote the output.  Note that whitespace and special
(shell-dependent) characters can cause havoc in this mode (like they
do with other
.BR getopt (1)
implementations).
.TP
.BR \-V , " \-\-version"
Display version information and exit.  No other output is generated.
.SH PARSING
This section specifies the format of the second part of the
parameters of
.B getopt
(the
.I parameters
in the
.BR SYNOPSIS ).
The next section
.RB ( OUTPUT )
describes the output that is generated.  These parameters were
typically the parameters a shell function was called with.  Care must
be taken that each parameter the shell function was called with
corresponds to exactly one parameter in the parameter list of
.B getopt
(see the
.BR EXAMPLES ).
All parsing is done by the GNU
.BR getopt (3)
routines.
.PP
The parameters are parsed from left to right.  Each parameter is
classified as a short option, a long option, an argument to an
option, or a non\-option parameter.
.PP
A simple short option is a
.RB ' \- '
followed by a short option character.  If the option has a required
argument, it may be written directly after the option character or as
the next parameter (i.e., separated by whitespace on the command
line).  If the option has an optional argument, it must be written
directly after the option character if present.
.PP
It is possible to specify several short options after one
.RB ' \- ',
as long as all (except possibly the last) do not have required or
optional arguments.
.PP
A long option normally begins with
.RB ' \-\- '
followed by the long option name.  If the option has a required
argument, it may be written directly after the long option name,
separated by
.RB ' = ',
or as the next argument (i.e., separated by whitespace on the command
line).  If the option has an optional argument, it must be written
directly after the long option name, separated by
.RB ' = ',
if present (if you add the
.RB ' = '
but nothing behind it, it is interpreted as if no argument was
present; this is a slight bug, see the
.BR BUGS ).
Long options may be abbreviated, as long as the abbreviation is not
ambiguous.
.PP
Each parameter not starting with a
.RB ' \- ',
and not a required argument of a previous option, is a non\-option
parameter.  Each parameter after a
.RB ' \-\- '
parameter is always interpreted as a non\-option parameter.  If the
environment variable
.B POSIXLY_CORRECT
is set, or if the short option string started with a
.RB ' + ',
all remaining parameters are interpreted as non\-option parameters as
soon as the first non\-option parameter is found.
.SH OUTPUT
Output is generated for each element described in the previous
section.  Output is done in the same order as the elements are
specified in the input, except for non\-option parameters.  Output
can be done in
.I compatible
.RI ( unquoted )
mode, or in such way that whitespace and other special characters
within arguments and non\-option parameters are preserved (see
.BR QUOTING ).
When the output is processed in the shell script, it will seem to be
composed of distinct elements that can be processed one by one (by
using the shift command in most shell languages).  This is imperfect
in unquoted mode, as elements can be split at unexpected places if
they contain whitespace or special characters.
.PP
If there are problems parsing the parameters, for example because a
required argument is not found or an option is not recognized, an
error will be reported on stderr, there will be no output for the
offending element, and a non\-zero error status is returned.
.PP
For a short option, a single
.RB ' \- '
and the option character are generated as one parameter.  If the
option has an argument, the next parameter will be the argument.  If
the option takes an optional argument, but none was found, the next
parameter will be generated but be empty in quoting mode, but no
second parameter will be generated in unquoted (compatible) mode.
Note that many other
.BR getopt (1)
implementations do not support optional arguments.
.PP
If several short options were specified after a single
.RB ' \- ',
each will be present in the output as a separate parameter.
.PP
For a long option,
.RB ' \-\- '
and the full option name are generated as one parameter.  This is
done regardless whether the option was abbreviated or specified with
a single
.RB ' \- '
in the input.  Arguments are handled as with short options.
.PP
Normally, no non\-option parameters output is generated until all
options and their arguments have been generated.  Then
.RB ' \-\- '
is generated as a single parameter, and after it the non\-option
parameters in the order they were found, each as a separate
parameter.  Only if the first character of the short options string
was a
.RB ' \- ',
non\-option parameter output is generated at the place they are found
in the input (this is not supported if the first format of the
.B SYNOPSIS
is used; in that case all preceding occurrences of
.RB ' \- '
and
.RB ' + '
are ignored).
.SH QUOTING
In compatible mode, whitespace or 'special' characters in arguments
or non\-option parameters are not handled correctly.  As the output
is fed to the shell script, the script does not know how it is
supposed to break the output into separate parameters.  To circumvent
this problem, this implementation offers quoting.  The idea is that
output is generated with quotes around each parameter.  When this
output is once again fed to the shell (usually by a shell
.B eval
command), it is split correctly into separate parameters.
.PP
Quoting is not enabled if the environment variable
.B GETOPT_COMPATIBLE
is set, if the first form of the
.B SYNOPSIS
is used, or if the option
.RB ' \-u '
is found.
.PP
Different shells use different quoting conventions.  You can use the
.RB ' \-s '
option to select the shell you are using.  The following shells are
currently supported:
.RB ' sh ',
.RB ' bash ',
.RB ' csh '
and
.RB ' tcsh '.
Actually, only two 'flavors' are distinguished: sh\-like quoting
conventions and csh\-like quoting conventions.  Chances are that if
you use another shell script language, one of these flavors can still
be used.
.SH "SCANNING MODES"
The first character of the short options string may be a
.RB ' \- '
or a
.RB ' + '
to indicate a special scanning mode.  If the first calling form in
the
.B SYNOPSIS
is used they are ignored; the environment variable
.B POSIXLY_CORRECT
is still examined, though.
.PP
If the first character is
.RB ' + ',
or if the environment variable
.B POSIXLY_CORRECT
is set, parsing stops as soon as the first non\-option parameter
(i.e., a parameter that does not start with a
.RB ' \- ')
is found that is not an option argument.  The remaining parameters
are all interpreted as non\-option parameters.
.PP
If the first character is a
.RB ' \- ',
non\-option parameters are outputted at the place where they are
found; in normal operation, they are all collected at the end of
output after a
.RB ' \-\- '
parameter has been generated.  Note that this
.RB ' \-\- '
parameter is still generated, but it will always be the last
parameter in this mode.
.SH COMPATIBILITY
This version of
.BR getopt (1)
is written to be as compatible as possible to other versions.
Usually you can just replace them with this version without any
modifications, and with some advantages.
.PP
If the first character of the first parameter of getopt is not a
.RB ' \- ',
.B getopt
goes into compatibility mode.  It will interpret its first
parameter as the string of short options, and all other arguments
will be parsed.  It will still do parameter shuffling (i.e., all
non\-option parameters are output at the end), unless the
environment variable
.B POSIXLY_CORRECT
is set.
.PP
The environment variable
.B GETOPT_COMPATIBLE
forces
.B getopt
into compatibility mode.  Setting both this environment variable and
.B POSIXLY_CORRECT
offers 100% compatibility for 'difficult' programs.  Usually, though,
neither is needed.
.PP
In compatibility mode, leading
.RB ' \- '
and
.RB ' + '
characters in the short options string are ignored.
.SH RETURN CODES
.B getopt
returns error code
.B 0
for successful parsing,
.B 1
if
.BR getopt (3)
returns errors,
.B 2
if it does not understand its own parameters,
.B 3
if an internal error occurs like out\-of\-memory, and
.B 4
if it is called with
.BR \-T .
.SH EXAMPLES
Example scripts for (ba)sh and (t)csh are provided with the
.BR getopt (1)
distribution, and are optionally installed in
.I /usr/share/getopt/
or
.I /usr/share/doc/
in the util-linux subdirectory.
.SH ENVIRONMENT
.IP POSIXLY_CORRECT
This environment variable is examined by the
.BR getopt (3)
routines.  If it is set, parsing stops as soon as a parameter is
found that is not an option or an option argument.  All remaining
parameters are also interpreted as non\-option parameters, regardless
whether they start with a
.RB ' \- '.
.IP GETOPT_COMPATIBLE
Forces
.B getopt
to use the first calling format as specified in the
.BR SYNOPSIS .
.SH BUGS
.BR getopt (3)
can parse long options with optional arguments that are given an
empty optional argument (but cannot do this for short options).
This
.BR getopt (1)
treats optional arguments that are empty as if they were not present.
.PP
The syntax if you do not want any short option variables at all is
not very intuitive (you have to set them explicitly to the empty
string).
.SH AUTHOR
.MT frodo@frodo.looijaard.name
Frodo Looijaard
.ME
.SH "SEE ALSO"
.BR bash (1),
.BR tcsh (1),
.BR getopt (3)
.SH AVAILABILITY
The getopt command is part of the util-linux package and is available from
.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
Linux Kernel Archive
.UE .