Tribblix: manual page: getopts.1

GETOPTS(1) User Commands GETOPTS(1)

NAME

getopts - parse utility options

SYNOPSIS

/usr/bin/getopts optstring name [arg...]

sh
getopts optstring name [argument]...

ksh
getopts optstring name [arg]...

ksh93
getopts [-a name] optstring name [arg]...

DESCRIPTION

/usr/bin/getopts
The getopts utility can be used to retrieve options and option-
arguments from a list of parameters.

Each time it is invoked, the getopts utility places the value of the
next option in the shell variable specified by the name operand and
the index of the next argument to be processed in the shell variable
OPTIND. Whenever the shell is invoked, OPTIND is initialized to 1.

When the option requires an option-argument, the getopts utility
places it in the shell variable OPTARG. If no option was found, or if
the option that was found does not have an option-argument, OPTARG is
unset.

If an option character not contained in the optstring operand is
found where an option character is expected, the shell variable
specified by name is set to the question-mark ( ? ) character. In
this case, if the first character in optstring is a colon (:, the
shell variable OPTARG is set to the option character found, but no
output is written to standard error; otherwise, the shell variable
OPTARG is unset and a diagnostic message is written to standard
error. This condition is considered to be an error detected in the
way arguments were presented to the invoking application, but is not
an error in getopts processing.

If an option-argument is missing:

o If the first character of optstring is a colon, the shell
variable specified by name is set to the colon character
and the shell variable OPTARG is set to the option
character found.

o Otherwise, the shell variable specified by name is set to
the question-mark character (?), the shell variable OPTARG
is unset, and a diagnostic message is written to standard
error. This condition is considered to be an error
detected in the way arguments were presented to the
invoking application, but is not an error in getopts
processing; a diagnostic message is written as stated, but
the exit status is zero.

When the end of options is encountered, the getopts utility exits
with a return value greater than zero; the shell variable OPTIND is
set to the index of the first non-option-argument, where the first --
argument is considered to be an option-argument if there are no other
non-option-arguments appearing before it, or the value $# + 1 if
there are no non-option-arguments; the name variable is set to the
question-mark character. Any of the following identifies the end of
options: the special option --, finding an argument that does not
begin with a -, or encountering an error.

The shell variables OPTIND and OPTARG are local to the caller of
getopts and are not exported by default.

The shell variable specified by the name operand, OPTIND and OPTARG
affect the current shell execution environment.

If the application sets OPTIND to the value 1, a new set of
parameters can be used: either the current positional parameters or
new arg values. Any other attempt to invoke getopts multiple times
in a single shell execution environment with parameters (positional
parameters or arg operands) that are not the same in all invocations,
or with an OPTIND value modified to be a value other than 1, produces
unspecified results.

sh
getopts is a built-in Bourne shell command used to parse positional
parameters and to check for valid options. See sh(1). It supports all
applicable rules of the command syntax standard (see Rules 3-10,
Intro(1)). It should be used in place of the getopt command.

optstring must contain the option letters the command using getopts
recognizes. If a letter is followed by a colon, the option is
expected to have an argument, or group of arguments, which must be
separated from it by white space.

Each time it is invoked, getopts places the next option in the shell
variable name and the index of the next argument to be processed in
the shell variable OPTIND. Whenever the shell or a shell script is
invoked, OPTIND is initialized to 1.

When an option requires an option-argument, getopts places it in the
shell variable OPTARG.

If an illegal option is encountered, ? is placed in name.

When the end of options is encountered, getopts exits with a non-zero
exit status. The special option - can be used to delimit the end of
the options.

By default, getopts parses the positional parameters. If extra
arguments (argument ...) are specified on the getopts command line,
getopts parses them instead.

/usr/lib/getoptcvt reads the shell script in filename, converts it to
use getopts instead of getopt, and writes the results on the standard
output.

So that all new commands adhere to the command syntax standard
described in Intro(1), they should use getopts or getopt to parse
positional parameters and check for options that are valid for that
command.

getopts prints an error message on the standard error when it
encounters an option letter not included in optstring.

Although the following command syntax rule (see Intro(1)) relaxations
are permitted under the current implementation, they should not be
used because they can not be supported in future releases of the
system. As in the EXAMPLES section below, -a and -b are options, and
the option -o requires an option-argument.

The following example violates Rule 5: options with option-arguments
must not be grouped with other options:

example% cmd -aboxxx filename

The following example violates Rule 6: there must be white space
after an option that takes an option-argument:

example% cmd -ab oxxx filename

Changing the value of the shell variable OPTIND or parsing different
sets of arguments can lead to unexpected results.

ksh
Checks arg for legal options. If arg is omitted, the positional
parameters are used. An option argument begins with a + or a -. An
option not beginning with + or - or the argument - ends the options.
optstring contains the letters that getopts recognizes. If a letter
is followed by a :, that option is expected to have an argument. The
options can be separated from the argument by blanks.

getopts places the next option letter it finds inside variable name
each time it is invoked with a + prepended when arg begins with a +.
The index of the next arg is stored in OPTIND. The option argument,
if any, gets stored in OPTARG.

A leading : in optstring causes getopts to store the letter of an
invalid option in OPTARG, and to set name to ? for an unknown option
and to : when a required option is missing. Otherwise, getopts prints
an error message. The exit status is non-zero when there are no more
options.

getopts supports both traditional single-character short options and
long options defined by Sun's Command Line Interface Paradigm (CLIP).

Each long option is an alias for a short option and is specified in
parentheses following its equivalent short option. For example, you
can specify the long option file as an alias for the short option f
using the following script line:

getopts "f(file)" opt

Precede long options on the command line with -- or ++. In the
example above, --file on the command line would be the equivalent of
-f, and ++file on the command line would be the equivalent of +f.

Each short option can have multiple long option equivalents, although
this is in violation of the CLIP specification and should be used
with caution. You must enclose each long option equivalent
parentheses, as follows:

getopts "f:(file)(input-file)o:(output-file)"

In the above example, both --file and --input-file are the equivalent
of -f, and --output-file is the equivalent of -o.

The variable name is always set to a short option. When a long option
is specified on the command line, name is set to the short-option
equivalent.

For a further discussion of the Korn shell's getopts built-in
command, see the previous discussion in the Bourne shell (sh) section
of this manpage.

ksh93
The getopts utility can be used to retrieve options and arguments
from a list of arguments specified by args or the positional
parameters if arg is omitted. It can also generate usage messages and
a manual page for the command based on the information in optstring.

Each time it is invoked, the getopts utility places the value of the
next option in the shell variable specified by the name operand and
the index of the next argument to be processed in the shell variable
OPTIND. When the shell is invoked OPTIND is initialized to 1. When an
option requires or permits an option argument, getopts places the
option argument in the shell variable OPTARG. Otherwise OPTARG is set
to 1 when the option is set and 0 when the option is unset.

The optstring string consists of alphanumeric characters, the special
characters +, -, ?, :, and SPACE or character groups enclosed in
[...]. Character groups can be nested in {...}. Outside of a [...]
group, a single NEWLINE followed by zero or more blanks is ignored.
One or more blank lines separate the options from the command
argument synopsis.

Each [...] group consists of an optional label, optional attributes
separated by :, and an optional description string following ?. The
characters from the ? to the end of the next ] are ignored for option
parsing and short usage messages. They are used for generating
verbose help or man pages. The : character can not appear in the
label. The ? character must be specified as ?? in the label and the ]
character must be specified as ]] in the description string. Text
between two \b (backspace) characters indicates that the text should
be emboldened when displayed. Text between two \a (bell) characters
indicates that the text should be emphasized or italicized when
displayed. Text between two \v (vertical tab) characters indicates
that the text should displayed in a fixed-width font. Text between
two \f (form feed) characters is replaced by the output from the
shell function whose name is that of the enclosed text.

All output from this interface is written to the standard error.

There are several group types:

1. A group of the form

[-[version][flag[number]]...[?text]]

which appears as the first group enables the extended
interface.

version specifies the interface version, currently 1. The
latest version is assumed if version is omitted. Future
enhancements can increment version, but all versions are
supported. text typically specifies an SCCS or CVS
identification string. Zero or more flags with optional
number values can be specified to control option parsing.
The flags are:

c
Cache this optstring for multiple passes. Used to optimize
built-ins that can be called many times within the same
process.

i
Ignore this optstring when generating help. Used when
combining optstring values from multiple passes.

l
Display only long option names in help messages.

o
The - option character prefix is optional. This supports the
obsolete ps(1) option syntax.

p
The number specifies the number of - characters that must
prefix long option names. The default is 2. 0, 1 or 2 are
accepted, for example p0 for dd(8) and p1 for find(1).

s
The number specifies the manual page section number, 1 by
default.

2. An option specification of the form
[option[!][=number][:longname][?text]]. In this case the
first field is the option character, which is the value
returned in the name operand when the option is matched.
If there is no option character then a two or more digit
number should be specified. This number is returned as the
value of the name operand if the long option is matched.
If option is followed by a ! then the option character
sense is the inverse of the longname sense. For options
that do not take values OPTARG is set to 0 for ! inverted
option characters and 1 otherwise. =number optionally
specifies a number to be returned in the name operand
instead of the option character. A longname is specified
by --longname and is matched by the shortest non-ambiguous
prefix of all long options. An * in the longname field
indicates that only characters up to that point need to
match, provided any additional characters match exactly.
The enclosing [ and ] can be omitted for an option that
does not have a longname or descriptive text.

3. An option argument specification. Options that take
arguments can be followed by :, indicating a string value
or #, indicating a numeric value, and an option argument
specification. An option argument specification consists
of the option argument name as field 1. The remaining :
separated fields are a type name and zero or more of the
special attribute words listof, oneof, and ignorecase. A
default option value can be specified in the final field
as :=default. The option argument specification can be
followed by a list of option value descriptions enclosed
in braces. A long option that takes an argument is
specified as --longname=value. If the : or # is followed
by ?, the option argument is optional. If only the option
character form is specified then the optional argument
value is not set if the next argument starts with - or +.

4. An option value description.

5. An argument specification. A list of valid option argument
values can be specified by enclosing them inside a {...}
following the option argument specification. Each of the
permitted values can be specified with a [...] containing
the value followed by a description.

6. A group of the form [+\n...] displays the characters
representing ... in fixed-width font without adding line
breaks.

7. A group of the form [+name?text] specifies a section name
with descriptive text. If name is omitted, text is placed
in a new paragraph.

8. A group of the form [-name?text] specifies entries for the
IMPLEMENTATION section.

If the leading character of optstring is +, arguments beginning with
+ are also be considered options.

A leading : character or a : following a leading + in optstring
affects the way errors are handled. If an option character or
longname argument not specified in optstring is encountered when
processing options, the shell variable whose name is name is set to
the ? character. The shell variable OPTARG is set to the character
found. If an option argument is missing or has an invalid value, then
name is set to the : character and the shell variable OPTARG is set
to the option character found. Without the leading :, name is set to
the ? character, OPTARG is unset, and an error message is written to
standard error when errors are encountered.

The end of options occurs when:

1. The special argument -- is encountered.

2. An argument that does not begin with a - is encountered.

3. A help argument is specified.

4. An error is encountered.

If OPTIND is set to the value 1, a new set of arguments can be used.

getopts can also be used to generate help messages containing command
usage and detailed descriptions. Specify args as:

-?
Use this to generate a usage synopsis.

--??
Use this to generate a verbose usage message.

--??man
Use this to generate a formatted manual page.

--??api
Use this to generate an easy to parse usage message.

--??html
Use this to generate a man page in html format.

--??nroff
Use this to generate a man page in nroff format.

--??usage
Use this to list the current optstring.

--???name
Use this to list version=n, where n is greater than 0,
if the option name is recognized by getopts.

When the end of options is encountered, getopts exits with a non-zero
return value and the variable OPTIND is set to the index of the first
non-option argument.

OPTIONS

ksh93
The following options are supported by ksh93:

-a name
Use name instead of the command name in usage messages.

OPERANDS

The following operands are supported:

optstring
A string containing the option characters recognised by
the utility invoking getopts. If a character is followed
by a colon, the option is expected to have an argument,
which should be supplied as a separate argument.
Applications should specify an option character and its
option-argument as separate arguments, but getopts
interprets the characters following an option character
requiring arguments as an argument whether or not this
is done. An explicit null option-argument need not be
recognised if it is not supplied as a separate argument
when getopts is invoked; see getopt(3C). The characters
question-mark (?) and colon (:) must not be used as
option characters by an application. The use of other
option characters that are not alphanumeric produces
unspecified results. If the option-argument is not
supplied as a separate argument from the option
character, the value in OPTARG is stripped of the option
character and the -. The first character in optstring
determines how getopts behaves if an option character is
not known or an option-argument is missing.

name
The name of a shell variable that is set by the getopts
utility to the option character that was found.

The getopts utility by default parses positional parameters passed to
the invoking shell procedure. If args are specified, they are parsed
instead of the positional parameters.

USAGE

Since getopts affects the current shell execution environment, it is
generally provided as a shell regular built-in. If it is called in a
subshell or separate utility execution environment, such as one of
the following:

(getopts abc value "$@")
nohup getopts ...
find . -exec getopts ... \;

it does not affect the shell variables in the caller's environment.

Notice that shell functions share OPTIND with the calling shell even
though the positional parameters are changed. Functions that want to
use getopts to parse their arguments usually want to save the value
of OPTIND on entry and restore it before returning. However, there
are cases when a function wants to change OPTIND for the calling
shell.

EXAMPLES

Example 1: Parsing and Displaying Arguments

The following example script parses and displays its arguments:

aflag=
bflag=
while getopts ab: name
do
case $name in
a) aflag=1;;
b) bflag=1
bval="$OPTARG";;
?) printf "Usage: %s: [-a] [-b value] args\n" $0
exit 2;;
esac
done
if [ ! -z "$aflag" ]; then
printf "Option -a specified\n"
fi
if [ ! -z "$bflag" ]; then
printf 'Option -b "%s" specified\n' "$bval"
fi
shift $(($OPTIND - 1))
printf "Remaining arguments are: %s\n" "$*"

Example 2: Processing Arguments for a Command with Options

The following fragment of a shell program processes the arguments for
a command that can take the options -a or -b. It also processes the
option -o, which requires an option-argument:

while getopts abo: c
do
case $c in
a | b) FLAG=$c;;
o) OARG=$OPTARG;;
\?) echo $USAGE
exit 2;;
esac
done
shift `expr $OPTIND - 1`

Example 3: Equivalent Code Expressions

This code example accepts any of the following as equivalent:

cmd -a -b -o "xxx z yy" filename
cmd -a -b -o "xxx z yy" -- filename
cmd -ab -o xxx,z,yy filename
cmd -ab -o "xxx z yy" filename
cmd -o xxx,z,yy -b -a filename

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment
variables that affect the execution of getopts: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, and NLSPATH.

OPTIND
This variable is used by getopts as the index of the next
argument to be processed.

OPTARG
This variable is used by getopts to store the argument if
an option is using arguments.

EXIT STATUS

The following exit values are returned:

0
An option, specified or unspecified by optstring, was found.

>0
The end of options was encountered or an error occurred.

ksh93
The following exit values are returned by ksh93:

0
A specified option was found.

1
An end of options was encountered.

2
A usage or information message was generated.

ATTRIBUTES

DIAGNOSTICS

Whenever an error is detected and the first character in the
optstring operand is not a colon (:), a diagnostic message is written
to standard error with the following information in an unspecified
format:

o The invoking program name is identified in the message.
The invoking program name is the value of the shell
special parameter 0 at the time the getopts utility is
invoked. A name equivalent to

basename "$0"

can be used.

o If an option is found that was not specified in optstring,
this error is identified and the invalid option character
is identified in the message.

o If an option requiring an option-argument is found, but an
option-argument is not found, this error is identified and
the invalid option character is identified in the message.

November 2, 2007 GETOPTS(1)