$XDG_DATA_HOME defines the base directory relative to which user specific data files should be stored. If $XDG_DATA_HOME is either not set or empty, a default equal to $HOME/.local/share should be used.

$XDG_CONFIG_HOME defines the base directory relative to which user specific configuration files should be stored. If $XDG_CONFIG_HOME is either not set or empty, a default equal to $HOME/.config should be used.

$XDG_DATA_DIRS defines the preference-ordered set of base directories to search for data files in addition to the $XDG_DATA_HOME base directory. The directories in $XDG_DATA_DIRS should be seperated with a colon ‘:‘.

If $XDG_DATA_DIRS is either not set or empty, a value equal to /usr/local/share/:/usr/share/ should be used.

$XDG_CONFIG_DIRS defines the preference-ordered set of base directories to search for configuration files in addition to the $XDG_CONFIG_HOME base directory. The directories in $XDG_CONFIG_DIRS should be seperated with a colon ‘:‘.

If $XDG_CONFIG_DIRS is either not set or empty, a value equal to /etc/xdg should be used.

The order of base directories denotes their importance; the first directory listed is the most important. When the same information is defined in multiple places the information defined relative to the more important base directory takes precedent. The base directory defined by $XDG_DATA_HOME is considered more important than any of the base directories defined by $XDG_DATA_DIRS. The base directory defined by $XDG_CONFIG_HOME is considered more important than any of the base directories defined by $XDG_CONFIG_DIRS.

$XDG_CACHE_HOME defines the base directory relative to which user specific non-essential data files should be stored. If $XDG_CACHE_HOME is either not set or empty, a default equal to $HOME/.cache should be used.

$XDG_RUNTIME_DIR defines the base directory relative to which user-specific non-essential runtime files and other file objects (such as sockets, named pipes, ...) should be stored. The directory MUST be owned by the user, and he MUST be the only one having read and write access to it. Its Unix access mode MUST be 0700.

<?xml version="1.0"?><!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
 <dir>~/.fonts</dir>

<match>
        <test name="lang" compare="contains">
                <string>zh</string>
        </test>
        <test name="family">
                <string>serif</string>
        </test> 
        <edit name="family" mode="prepend">
                <string>Source Han Sans CN</string>
        </edit>
</match>

<match>
        <test name="lang" compare="contains">
                <string>zh</string>
        </test>
        <test name="family">
                <string>sans</string>
        </test>
        <edit name="family" mode="prepend">
                <string>Source Han Sans CN</string>
        </edit>
</match>

<match>
        <test name="lang" compare="contains">
                <string>zh</string>
        </test>
        <test name="family">
                <string>mono</string>
        </test>
        <edit name="family" mode="prepend">
                <string>Source Han Sans CN</string>
        </edit>
</match>

</fontconfig>

<?xml version="1.0"?><!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
 <dir>~/.fonts</dir>

<alias>
        <family>serif</family>
        <prefer>
                <family>DejaVu Serif</family>
                <family>Source Han Sans CN</family>
        </prefer>
</alias>

<alias>
        <family>sans serif</family>
        <prefer>
                <family>DejaVu Sans</family>
                <family>Source Han Sans CN</family>
        </prefer>
</alias>

<alias>
        <family>sans</family>
        <prefer>
                <family>DejaVu Sans</family>
                <family>Source Han Sans CN</family>
        </prefer>
</alias>

<alias>
        <family>mono</family>
        <prefer>
                <family>DejaVu Sans Mono</family>
                <family>Source Han Sans CN</family>
        </prefer>
</alias>

</fontconfig>

[tong@T7:~]
% fc-match -a serif > 3
[tong@T7:~]
% fc-match -s serif > 33
[tong@T7:~]
% diff 1 3
8a9,15
> SourceHanSansCN-Regular.otf: "Source Han Sans CN" "Regular"
> SourceHanSansCN-Normal.otf: "Source Han Sans CN" "Normal"
> SourceHanSansCN-Light.otf: "Source Han Sans CN" "Light"
> SourceHanSansCN-ExtraLight.otf: "Source Han Sans CN" "ExtraLight"
> SourceHanSansCN-Medium.otf: "Source Han Sans CN" "Medium"
> SourceHanSansCN-Bold.otf: "Source Han Sans CN" "Bold"
> SourceHanSansCN-Heavy.otf: "Source Han Sans CN" "Heavy"
247d253
< SourceHanSansCN-Regular.otf: "Source Han Sans CN" "Regular"
363d368
< SourceHanSansCN-Normal.otf: "Source Han Sans CN" "Normal"
369d373
< SourceHanSansCN-Light.otf: "Source Han Sans CN" "Light"
372d375
< SourceHanSansCN-ExtraLight.otf: "Source Han Sans CN" "ExtraLight"
377d379
< SourceHanSansCN-Medium.otf: "Source Han Sans CN" "Medium"
527d528
< SourceHanSansCN-Bold.otf: "Source Han Sans CN" "Bold"
553d553
< SourceHanSansCN-Heavy.otf: "Source Han Sans CN" "Heavy"
[tong@T7:~]
% diff 11 33                                                                                                     1 ?
4a5
> SourceHanSansCN-Regular.otf: "Source Han Sans CN" "Regular"
14d14
< MSJH.TTC: "Microsoft JhengHei" "Normal"
79d78
< SourceHanSansCN-Regular.otf: "Source Han Sans CN" "Regular"
[tong@T7:~]

<?xml version="1.0"?><!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
 <dir>~/.fonts</dir>

<alias>
        <family>serif</family>
        <prefer>
                <family>DejaVu Serif</family>
                <family>Source Han Sans CN</family>
        </prefer>
</alias>

<alias>
        <family>sans-serif</family>
        <prefer>
                <family>DejaVu Sans</family>
                <family>Source Han Sans CN</family>
        </prefer>
</alias>

<alias>
        <family>monospace</family>
        <prefer>
                <family>DejaVu Sans Mono</family>
                <family>Source Han Sans CN</family>
        </prefer>
</alias>

</fontconfig>