The most common actions for user-selected variants is to add or remove dependencies, configure arguments, and build arguments according to various options a port author wishes to provide. Here is an example of several variants that modify depends_lib and configure arguments for a port.

variant fastcgi description {Add fastcgi binary} {
    configure.args-append \
            --enable-fastcgi \
            --enable-force-cgi-redirect \
            --enable-memory-limit
}

variant gmp description {Add GNU MP functions} {
    depends_lib-append port:gmp
    configure.args-append --with-gmp=${prefix}

}

variant sqlite description {Build sqlite support} {
    depends_lib-append \
        port:sqlite3
    configure.args-delete \
        --without-sqlite \
        --without-pdo-sqlite
    configure.args-append \
        --with-sqlite \
        --with-pdo-sqlite=${prefix} \
        --enable-sqlite-utf8
}

In the example variant declaration below, the configure argument --without-x is removed and a number of others are appended.

variant x11 description {Builds port as an X11 program with Lucid widgets} {
    configure.args-delete   --without-x
    configure.args-append   --with-x-toolkit=lucid \
                            --without-carbon \
                            --with-xpm \
                            --with-jpeg \
                            --with-tiff \
                            --with-gif \
                            --with-png
    depends_lib-append      lib:libX11:XFree86 \
                            lib:libXpm:XFree86 \
                            port:jpeg \
                            port:tiff \
                            port:libungif \
                            port:libpng
}

If a variant requires options in addition to those provided by keywords using -append and/or -delete, in other words, any actions that would normally take place within a port installation phase, do not try to do this within the variant declaration. Rather, modify the behavior of any affected phases when the variant is invoked using the variant_isset keyword.

post-destroot {
    xinstall -m 755 -d ${destroot}${prefix}/etc/
    xinstall ${worksrcpath}/examples/foo.conf \
        ${destroot}${prefix}/etc/

    if {[variant_isset carbon]} {
        delete ${destroot}${prefix}/bin/emacs
        delete ${destroot}${prefix}/bin/emacs-${version}
    }
}

Variants are used to specify actions that lie outside the core functions of an application or port, but there may be some cases where you wish to specify these non-core functions by default. For this purpose you may use the keyword default_variants.

default_variants    +foo +bar