Manual Reference Pages - OPTIONS (1)
options - a general description of the AIM tools options handler.
command line ::= <program name> [<options>] [<filename>]
option ::= <flag option> | <valued option>
flag option ::= -<name> | [-]<name>=on|off
valued option ::= -<name>[=]<value> | [-]<name>=<value>
A program may take one or more files as input, and several options to set internal parameters. The function of the options handler is to parse the command line and interpret options according to the defined syntax, to assign internal default values to the internal parameters represented by each option, and then to override these using any corresponding options found on the command line.
Command line syntax
Programs which do not read input from files have a command line:
<program name> [<options>]
Programs which expect to read input from one or more files have command line syntax:
<program name> [<options>] [<filenames>]
The command line parser assumes that each space-separated token on the command line is either an option or a filename. The strategy is to parse the command line until either it is empty or a token with invalid option syntax is found. All tokens remaining on the command line after parsing are assumed to be input filenames. Programs which read from one or more files expect the filenames to be given as the final arguments on the command line. If the command line is empty after parsing the options, but a file is expected, then input is read from the standard input, (eg. via re-direction or a pipe). The filename - is also interpreted as the standard input.
Typographical errors which cause options to have bad syntax are therefore treated as potential filenames. The program reports the error as if it were a file not found, by printing a message on the stderr:
<program name>: cant open <option>
and quits with an exit status of 1. In the (unlikely) event that a file with a name matching the error is found then this file will be opened for input to the program.
The general syntax for flag options (which do not take a <value> part) is:
-<name> | [-]<name>=on|off
The general syntax for valued options is:
-<name>[=]<value> | [-]<name>=<value>
The usual Unix notation is observed, (characters within square brackets are optional and the bar sign denotes exclusive OR) so that flag options may take any of the forms:
-<name> -<name>=on <name>=on -<name>=off <name>=off
Similarly, valued options may take any of the forms:
-<name><value> -<name>=<value> <name>=<value>
Option syntax is designed to be compatible between a Unix options style and a more declarative style. This is facilitated by allowing the <name> part of each option to be given in abbreviated form provided this is unambiguous with other options for the program.
The general option syntax in Unix and the declarative style respectively is:
An example of the same option in both styles respectively would be:
In many cases the option names are designed to be unambiguous from the first letter to allow for complete compatibility, but in some cases the need for declarative option names was felt to override the need for absolute compatibility. If necessary any option name can easily be changed by changing the name given in the first field of the static Options structure defined near the top of each program source code, and then re-compile the program. The change affects only the user interface via the options handler and has no other side effects.
An exact match for option <name> is unambiguous even if the <name> matches the head of another option <name>.
If insufficient of the <name> part is given to disambiguate it from other options, then the program prints a message on the stderr:
<program name>: ambiguous option [<option>]
and quits with an exit status of 1.
For example, if a program takes options with names frames and frameshift then the following are synonymous for setting the frameshift to 20:
frameshift=20 framesh=20 -framesh20
but the following would be ambiguous:
However an exact match is allowed to be unambiguous, so that the following would set the frames option to 3:
The <value> part may take the form of a number with optional units. Time variables may be given in s (seconds) ms (milliseconds) and p (sample points). The default with no units is interpreted as sample points. For example:
10 10 samples 10p 10 samples 10s 10 seconds 10ms 10 milliseconds
Values given with time units are converted to a number of samples internally using the given samplerate option.
Frequency variables take Hz (Hertz) and kHz (KiloHertz). The default with no units is interpreted as Hertz.. For example:
20000 20000 Hertz 20000Hz 20000 Hertz 20kHz 20000 Hertz
A <value> may be given as a hyphen-separated range of values with the general syntax:
<value> = a[-b]
where a and b are both values or the strings "min" or "max". For example, the frame option is used to select a range of frames for processing:
frame=a Select just the ath frame. frame=a-b Select frames from the ath to bth inclusive. frame=min Select the first frame. frame=max Select the last frame. frame=a-max Select frames from the ath to the last inclusive. frame=min-b Select frames from the first to the bth inclusive.
Values which specify a time or frequency range take units as appropriate. For example:
All tools take an option called help which causes the program to print help information on the stdout. The following are usually synonymous calls for help:
<program name> -h <program name> -help <program name> help=on
In some cases the abbreviation -h will be ambiguous with another option name, however -help and help=on are always unambiguous. The help printed on the stdout includes a summary of the programs application, its command-line syntax or usage, and a list of the program options with their default values and a brief comment about the use of each option. The option syntax for each option is printed in place of option comment line when the call for help takes the form:
<program name> help=syntax
Help with particular named options can be called with:
<program name> help=<name>
where the <name> part can be abbreviated provided it is unambiguous. Certain options are silent in the sense that they are not printed in the options list by the standard call for help because they are considered to be rarely used. However they can be included in the options list by the call:
<program name> help=all
Silent options are assigned on the command line in the same way as ordinary options.
A filename which matches a typographical error in option name would be opened for input, leading to unexpected results.
Copyright (c) Applied Psychology Unit, Medical Research Council, 1995
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|SunOS 5.6||OPTIONS (1)||1 September 1993|