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7.1 AutoOpts Features

AutoOpts supports option processing; option state saving; and program documentation with innumerable features. Here, we list a few obvious ones and some important ones, but the full list is really defined by all the attributes defined in the Option Definitions section.

  1. POSIX-compliant short (flag) option processing.
  2. GNU-style long options processing. Long options are recognized without case sensitivity, and they may be abbreviated.
  3. Environment variable initializations, See section environment variable presets.
  4. Initialization from configuration files (aka RC or INI files), and saving the option state back into one, See section configuration file presets.
  5. Config files may be partitioned. One config file may be used by several programs by partitioning it with lines containing, [PROGRAM_NAME] or <?program-name>, See section configuration file presets.
  6. Config files may contain AutoOpts directives. <?auto-options [[option-text]]> may be used to set AutoOpts option processing options. Viz., GNU usage layout versus AutoOpts conventional layout, and misuse-usage versus no-misuse-usage, See section Usage and Version Info Display.
  7. Options may be marked as dis-abled with a disablement prefix. Such options may default to either an enabled or a disabled state. You may also provide an enablement prefix, too, e.g., ‘--allow-mumble’ and ‘--prevent-mumble’ (see section Common Option Attributes).
  8. Verify that required options are present between the minimum and maximum number of times on the command line. Verify that conflicting options do not appear together. Verify that options requiring the presence of other options are, in fact, used in the presence of other options. See See section Common Option Attributes, and See section Option Conflict Attributes.
  9. There are several automatically supported options. They will have short flags if any options have option flags and the flags are not suppressed. The associated flag may be altered or suppressed by specifying no value or an alternate character for xxx-value; in the option definition file. xxx is the name of the option below:

    These are always available. ‘--more-help’ will pass the full usage text through a pager.


    This is added to the option list if usage-opt is specified. It yields the abbreviated usage to ‘stdout’.


    This is added to the option list if version = xxx; is specified.


    These are added to the option list if homerc is specified. Mostly. If, disable-save is specified, then ‘--save-opts’ is disabled.

  10. Various forms of main procedures can be added to the output, See section Generating main procedures. There are four basic forms:
    1. A program that processes the arguments and writes to standard out portable shell commands containing the digested options.
    2. A program that will generate portable shell commands to parse the defined options. The expectation is that this result will be copied into a shell script and used there.
    3. A for-each main that will invoke a named function once for either each non-option argument on the command line or, if there are none, then once for each non-blank, non-comment input line read from stdin.
    4. A main procedure of your own design. Its code can be supplied in the option description template or by incorporating another template.
  11. There are several methods for handling option arguments.
  12. The generated usage text can be emitted in either AutoOpts standard format (maximizing the information about each option), or GNU-ish normal form. The default form is selected by either specifying or not specifying the gnu-usage attribute (see section Program Information Attributes). This can be overridden by the user himself with the AUTOOPTS_USAGE environment variable. If it exists and is set to the string ‘gnu’, it will force GNU-ish style format; if it is set to the string ‘autoopts’, it will force AutoOpts standard format; otherwise, it will have no effect.
  13. The usage text and many other strings are stored in a single character array (see section string table functions). This reduces fixup costs when loading the program or library. The downside is that if GCC detects that any of these strings are used in a printf format, you may get the warning, embedded '\0' in format. To eliminate the warning, you must provide GCC with the ‘-Wno-format-contains-nul’ option.
  14. If you compile with ENABLE_NLS defined and _() defined to a localization function (e.g. gettext(3GNU)), then the option processing code will be localizable (see section Internationalizing AutoOpts). Provided also that you do not define the no-xlate attribute to anything (see section User Presentation Attributes).

    You should also ensure that the ATTRIBUTE_FORMAT_ARG() gets #define-ed to something useful. There is an autoconf macro named AG_COMPILE_FORMAT_ARG in ‘ag_macros.m4’ that will set it appropriately for you. If you do not do this, then translated formatting strings may trigger GCC compiler warnings.

  15. Provides a callable routine to parse a text string as if it were from one of the rc/ini/config files, hereafter referred to as a configuration file.
  16. By adding a ‘doc’ and ‘arg-name’ attributes to each option, AutoGen will also be able to produce a man page and the ‘invoking’ section of a texinfo document.
  17. Intermingled option processing. AutoOpts options may be intermingled with command line operands and options processed with other parsing techniques. This is accomplished by setting the allow-errors (see section Program Description Attributes) attribute. When processing reaches a point where optionProcess (see section optionProcess) needs to be called again, the current option can be set with RESTART_OPT(n) (see section RESTART_OPT( n ) - Resume Option Processing) before calling optionProcess.

    See: See section Options for Library Code.

  18. Library suppliers can specify command line options that their client programs will accept. They specify option definitions that get #include-d into the client option definitions and they specify an "anchor" option that has a callback and must be invoked. That will give the library access to the option state for their options.
  19. library options. An AutoOpt-ed library may export its options for use in an AutoOpt-ed program. This is done by providing an option definition file that client programs #include into their own option definitions. See “AutoOpt-ed Library for AutoOpt-ed Program” (see section AutoOpt-ed Library for AutoOpt-ed Program) for more details.

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