feature-check - query a program for supported features

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.

Check for a single feature

Specify a program name and a feature name; the feature-check tool will exit with an exit code of 0 if the program supports it, and a non-zero exit code if the program doesn't support the feature or something goes wrong when querying it (e.g. it doesn't support the --features option at all):

#!/bin/sh

if feature-check confget ini; then
    # process an INI file with the confget tool
fi

If the program needs a different option to display its list of features, specify it using the feature-check tool's -O option:

[roam@straylight ~]$ feature-check curl AsynchDNS; echo $?
2
[roam@straylight ~]$ feature-check -O--version curl AsynchDNS; echo $?
0
[roam@straylight ~]$

To display the version of a feature advertised by the program, use the -v option:

[roam@straylight ~]$ feature-check -v timelimit subsecond
1.0
[roam@straylight ~]$

If the program's features output is on a line which starts with a marker other than "Features: ", specify it using the -P option.

Compare a single feature against a version number

After the program name, specify one or more arguments that, when all concatenated, form a "feature op version" string. The operation may be one of:

lt, <: the program's feature is at an earlier version
le, <=: the program's feature is at an earlier or the same version
eq, =: the program's feature is at the specified version
ge, >=: the program's feature is at a later or the same version
gt, >: the program's feature is at a later version

Here are some examples:

[roam@straylight ~]$ feature-check -l feature-check
feature-check   0.1.0
list    1.0
simple  1.0
single  1.0
[roam@straylight ~]$ feature-check feature-check 'simple <= 1.0' && echo yes
yes
[roam@straylight ~]$ feature-check feature-check 'simple lt 1.0a' && echo yes
yes
[roam@straylight ~]$ feature-check feature-check simple gt 1.0a && echo yes
[roam@straylight ~]$ feature-check feature-check simple lt 1.0.beta && echo yes
[roam@straylight ~]$ feature-check feature-check simple gt 1.0.beta && echo yes
yes

List a program's features

Specify the -l option and a program name; the feature-check tool will query the program's features and display them all. The default output format is one feature per line, name and value separated by a tab. The -o option allows specifying alternative output formats; the only one supported so far is json which outputs the features as a JSON object.

[roam@straylight ~]$ feature-check -l timelimit
subsecond       1.0
timelimit       1.9.0
[roam@straylight ~]$ feature-check -l -o json timelimit
{
   "subsecond" : "1.0",
   "timelimit" : "1.9.0"
}
[roam@straylight ~]$

Contact

The feature-check library was written by Peter Pentchev. It is developed in a GitLab repository. This documentation is hosted at Ringlet with a copy at ReadTheDocs.