NAME

     feature-check — query a program for supported features

SYNOPSIS

     feature-check [-v] [-O optname] [-P prefix] program feature-name
     feature-check [-O optname] [-P prefix] program feature-name op version
     feature-check [-O optname] [-o json|tsv] [-P prefix] -l program
     feature-check -V | -h
     feature-check --features

DESCRIPTION

     The feature-check tool obtains the list of supported features from a program via various
     methods (e.g. running it with the --features command-line option) and allows other programs
     to check for the presence and, possibly, versions of specific features.

     Options:

     --features
             List the compile-time features supported by this version of feature-check:

             feature-check
                     Always present, with the version of the feature-check tool.

             list    Present if the feature-check tool supports fetching the list of features
                     supported by a program.

             simple  Present if the feature-check tool supports comparing the version of a single
                     feature against a specified version string.

             single  Present if the feature-check tool supports querying a single feature.

     -h, --help
             Display program usage output and exit.

     -O optname
             Specify the option to pass to the program to obtain its list of features (default
             --features).

     -o format
             Specify the output format for the full list of features with the -l option.

     -P prefix
             Specify the prefix that feature-check should look for in the program's output to
             find the line that contains the list of features; default "Features: ".

     -V, --version
             Display program version output and exit.

     -v      When querying a single feature, output the version obtained for it.

EXIT STATUS

     When querying a single feature, feature-check will exit with code 0 if the program supports
     that feature, and with a non-zero code when either the program could not be executed, or its
     list of features could not be parsed, or the feature was not present.

     When examining the version of a single feature, feature-check will exit with code 0 if the
     comparison result is true, and with a non-zero code when either the program could not be
     executed, or its list of features could not be parsed, or the comparison failed.

     When listing the features supported by a program, feature-check will exit with code 0 when
     the list of features was obtained and output, and with a non-zero code when either the
     program could not be executed or its list of features could not be parsed.

EXAMPLES

     The following examples are shown as given to the shell:

           feature-check curl AsynchDNS

     Exit with code 0 if the curl(1) tool is present and it supports asynchronous DNS lookups.

           feature-check -l confget

     List the features supported by the confget(1) tool.

           feature-check timelimit 'timelimit ge 1.9'

     Exit with code 0 if the timelimit(1) tool advertises its timelimit feature at version 1.9 or
     later.

           feature-check timelimit timelimit ge 1.9

     The same check; note that the feature-check tool will treat all the arguments after the
     program name as a single expression, i.e. it will concatenate them into a single string
     separated by spaces and then interpret the string.

STANDARDS

     No standards documentation was harmed in the process of creating feature-check.

BUGS

     Please report any bugs in feature-check to the author.

AUTHOR

     The feature-check utility was written by Peter Pentchev <roam@ringlet.net> in 2018.