FONTS-CONF(5)                                                    FONTS-CONF(5)

       fonts.conf - Font configuration files


       Fontconfig is a library designed to provide system-wide font configura-
       tion, customization and application access.

       Fontconfig contains two essential  modules,  the  configuration  module
       which  builds an internal configuration from XML files and the matching
       module which accepts font patterns and  returns  the  nearest  matching

       The  configuration  module  consists of the FcConfig datatype, libexpat
       and FcConfigParse which walks over an XML tree and amends a  configura-
       tion  with data found within.  From an external perspective, configura-
       tion of the library consists of generating a valid XML tree and feeding
       that  to  FcConfigParse.  The only other mechanism provided to applica-
       tions for changing the running configuration is to add fonts and direc-
       tories to the list of application-provided font files.

       The intent is to make font configurations relatively static, and shared
       by as many applications as possible.  It is hoped that this  will  lead
       to  more  stable font selection when passing names from one application
       to another.  XML was chosen as a configuration file format  because  it
       provides  a  format which is easy for external agents to edit while re-
       taining the correct structure and syntax.

       Font configuration is separate from font matching; applications needing
       to  do  their  own matching can access the available fonts from the li-
       brary and perform private matching.  The intent is to  permit  applica-
       tions to pick and choose appropriate functionality from the library in-
       stead of forcing them to choose between this library and a private con-
       figuration  mechanism.  The hope is that this will ensure that configu-
       ration of fonts for all applications can be centralized in  one  place.
       Centralizing  font  configuration will simplify and regularize font in-
       stallation and customization.

       While font patterns may contain essentially any properties,  there  are
       some well known properties with associated types.  Fontconfig uses some
       of these properties for font matching and font completion.  Others  are
       provided as a convenience for the applications' rendering mechanism.

         Property        Type    Description
         family          String  Font family names
         familylang      String  Languages corresponding to each family
         style           String  Font style. Overrides weight and slant
         stylelang       String  Languages corresponding to each style
         fullname        String  Font full names (often includes style)
         fullnamelang    String  Languages corresponding to each fullname
         slant           Int     Italic, oblique or roman
         weight          Int     Light, medium, demibold, bold or black
         size            Double  Point size
         width           Int     Condensed, normal or expanded
         aspect          Double  Stretches glyphs horizontally before hinting
         pixelsize       Double  Pixel size
         spacing         Int     Proportional, dual-width, monospace or charcell
         foundry         String  Font foundry name
         antialias       Bool    Whether glyphs can be antialiased
         hinting         Bool    Whether the rasterizer should use hinting
         hintstyle       Int     Automatic hinting style
         verticallayout  Bool    Use vertical layout
         autohint        Bool    Use autohinter instead of normal hinter
         globaladvance   Bool    Use font global advance data (deprecated)
         file            String  The filename holding the font
         index           Int     The index of the font within the file
         ftface          FT_Face Use the specified FreeType face object
         rasterizer      String  Which rasterizer is in use (deprecated)
         outline         Bool    Whether the glyphs are outlines
         scalable        Bool    Whether glyphs can be scaled
         color           Bool    Whether any glyphs have color
         scale           Double  Scale factor for point->pixel conversions (deprecated)
         dpi             Double  Target dots per inch
         rgba            Int     unknown, rgb, bgr, vrgb, vbgr,
                                 none - subpixel geometry
         lcdfilter       Int     Type of LCD filter
         minspace        Bool    Eliminate leading from line spacing
         charset         CharSet Unicode chars encoded by the font
         lang            String  List of RFC-3066-style languages this
                                 font supports
         fontversion     Int     Version number of the font
         capability      String  List of layout capabilities in the font
         fontformat      String  String name of the font format
         embolden        Bool    Rasterizer should synthetically embolden the font
         embeddedbitmap  Bool    Use the embedded bitmap instead of the outline
         decorative      Bool    Whether the style is a decorative variant
         fontfeatures    String  List of the feature tags in OpenType to be enabled
         namelang        String  Language name to be used for the default value of
                                 familylang, stylelang, and fullnamelang
         prgname         String  String  Name of the running program
         postscriptname  String  Font family name in PostScript

       Fontconfig  performs matching by measuring the distance from a provided
       pattern to all of the available  fonts  in  the  system.   The  closest
       matching font is selected.  This ensures that a font will always be re-
       turned, but doesn't ensure that it is anything like the requested  pat-

       Font  matching starts with an application constructed pattern.  The de-
       sired attributes of the resulting font are collected together in a pat-
       tern.   Each  property  of  the pattern can contain one or more values;
       these are listed in priority order; matches earlier  in  the  list  are
       considered "closer" than matches later in the list.

       The  initial  pattern  is  modified by applying the list of editing in-
       structions specific to patterns found in the configuration;  each  con-
       sists  of  a match predicate and a set of editing operations.  They are
       executed in the order they appeared in the configuration.   Each  match
       causes the associated sequence of editing operations to be applied.

       After  the pattern has been edited, a sequence of default substitutions
       are performed to canonicalize the set  of  available  properties;  this
       avoids the need for the lower layers to constantly provide default val-
       ues for various font properties during rendering.

       The canonical font pattern is finally  matched  against  all  available
       fonts.   The distance from the pattern to the font is measured for each
       of several properties: foundry, charset, family, lang, spacing,  pixel-
       size,  style,  slant,  weight, antialias, rasterizer and outline.  This
       list is in priority order -- results of comparing earlier  elements  of
       this list weigh more heavily than later elements.

       There is one special case to this rule; family names are split into two
       bindings; strong and weak.   Strong  family  names  are  given  greater
       precedence  in the match than lang elements while weak family names are
       given lower precedence than lang elements.  This permits  the  document
       language  to  drive  font selection when any document specified font is

       The pattern representing that font is augmented to include any  proper-
       ties  found  in the pattern but not found in the font itself; this per-
       mits the application to pass rendering instructions or any  other  data
       through the matching system.  Finally, the list of editing instructions
       specific to fonts found in the configuration are applied  to  the  pat-
       tern.  This modified pattern is returned to the application.

       The  return value contains sufficient information to locate and raster-
       ize the font, including the file name, pixel size and  other  rendering
       data.  As none of the information involved pertains to the FreeType li-
       brary, applications are free to use any rasterization engine or even to
       take the identified font file and access it directly.

       The  match/edit  sequences  in  the  configuration are performed in two
       passes because there are essentially two different operations necessary
       -- the first is to modify how fonts are selected; aliasing families and
       adding suitable defaults.  The second is to  modify  how  the  selected
       fonts  are  rasterized.  Those must apply to the selected font, not the
       original pattern as false matches will often occur.

       Fontconfig provides a textual representation for patterns that the  li-
       brary  can  both  accept  and generate.  The representation is in three
       parts, first a list of family names, second a list of point  sizes  and
       finally a list of additional properties:

            <families>-<point sizes>:<name1>=<values1>:<name2>=<values2>...

       Values  in  a list are separated with commas.  The name needn't include
       either families or point sizes; they can be elided.  In addition, there
       are  symbolic  constants that simultaneously indicate both a name and a
       value.  Here are some examples:

         Name                            Meaning
         Times-12                        12 point Times Roman
         Times-12:bold                   12 point Times Bold
         Courier:italic                  Courier Italic in the default size
         Monospace:matrix=1 .1 0 1       The users preferred monospace font
                                         with artificial obliquing

       The '\', '-', ':' and ',' characters in family names must  be  preceded
       by a '\' character to avoid having them misinterpreted. Similarly, val-
       ues containing '\', '=', '_', ':' and ',' must also have them  preceded
       by  a  '\' character. The '\' characters are stripped out of the family
       name and values as the font name is read.

       To help diagnose font and applications problems,  fontconfig  is  built
       with  a  large  amount  of  internal debugging left enabled. It is con-
       trolled by means of the FC_DEBUG environment  variable.  The  value  of
       this  variable  is  interpreted  as  a number, and each bit within that
       value controls different debugging messages.

         Name         Value    Meaning
         MATCH            1    Brief information about font matching
         MATCHV           2    Extensive font matching information
         EDIT             4    Monitor match/test/edit execution
         FONTSET          8    Track loading of font information at startup
         CACHE           16    Watch cache files being written
         CACHEV          32    Extensive cache file writing information
         PARSE           64    (no longer in use)
         SCAN           128    Watch font files being scanned to build caches
         SCANV          256    Verbose font file scanning information
         MEMORY         512    Monitor fontconfig memory usage
         CONFIG        1024    Monitor which config files are loaded
         LANGSET       2048    Dump char sets used to construct lang values
         MATCH2        4096    Display font-matching transformation in patterns

       Add the value of the desired debug levels together and assign that  (in
       base 10) to the FC_DEBUG environment variable before running the appli-
       cation. Output from these statements is sent to stdout.

       Each font in the database contains a list  of  languages  it  supports.
       This is computed by comparing the Unicode coverage of the font with the
       orthography of each language.  Languages are tagged using  an  RFC-3066
       compatible  naming  and  occur in two parts -- the ISO 639 language tag
       followed a hyphen and then by the ISO 3166 country  code.   The  hyphen
       and country code may be elided.

       Fontconfig  has  orthographies for several languages built into the li-
       brary.  No provision has been made for adding new ones aside  from  re-
       building  the  library.  It currently supports 122 of the 139 languages
       named in ISO 639-1, 141 of the languages with two-letter codes from ISO
       639-2 and another 30 languages with only three-letter codes.  Languages
       with both two and three letter codes are provided  with  only  the  two
       letter code.

       For  languages  used  in  multiple territories with radically different
       character sets, fontconfig includes per-territory orthographies.   This
       includes Azerbaijani, Kurdish, Pashto, Tigrinya and Chinese.

       Configuration  files for fontconfig are stored in XML format; this for-
       mat makes external configuration tools easier to write and ensures that
       they  will  generate syntactically correct configuration files.  As XML
       files are plain text, they can also be manipulated by the  expert  user
       using a text editor.

       The  fontconfig document type definition resides in the external entity
       "fonts.dtd"; this is normally stored in the default font  configuration
       directory  (/etc/fonts).   Each  configuration  file should contain the
       following structure:

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

       This is the top level element for a font configuration and can  contain
       <dir>,  <cachedir>,  <include>, <match> and <alias> elements in any or-

       This element contains a directory name which will be scanned  for  font
       files  to  include in the set of available fonts. If 'prefix' is set to
       "xdg", the value in the  XDG_DATA_HOME  environment  variable  will  be
       added  as  the path prefix. please see XDG Base Directory Specification
       for more details.

       This element contains a directory name that is supposed to be stored or
       read the cache of font information.  If multiple elements are specified
       in the configuration file, the directory that can be accessed first  in
       the list will be used to store the cache files.  If it starts with '~',
       it refers to a directory in the users home directory.  If  'prefix'  is
       set to "xdg", the value in the XDG_CACHE_HOME environment variable will
       be added as the path prefix. please see XDG Base  Directory  Specifica-
       tion     for     more    details.     The    default    directory    is
       ``$XDG_CACHE_HOME/fontconfig'' and it contains the  cache  files  named
       ``<hash value>-<architecture>.cache-<version>'', where <version> is the
       fontconfig cache file version number (currently 7).

       This element contains the name of an additional configuration  file  or
       directory.   If  a directory, every file within that directory starting
       with an ASCII digit (U+0030  -  U+0039)  and  ending  with  the  string
       ``.conf''  will be processed in sorted order.  When the XML datatype is
       traversed by FcConfigParse, the contents of the file(s)  will  also  be
       incorporated  into  the configuration by passing the filename(s) to Fc-
       ConfigLoadAndParse.  If 'ignore_missing' is set to "yes" instead of the
       default  "no",  a missing file or directory will elicit no warning mes-
       sage from the library.  If 'prefix' is set to "xdg", the value  in  the
       XDG_CONFIG_HOME  environment variable will be added as the path prefix.
       please see XDG Base Directory Specification for more details.

       This element provides a place to consolidate  additional  configuration
       information.  <config> can contain <blank> and <rescan> elements in any

       Fonts often include "broken" glyphs which appear in  the  encoding  but
       are  drawn  as blanks on the screen.  Within the <blank> element, place
       each Unicode characters which is supposed to be blank in an <int>  ele-
       ment.   Characters outside of this set which are drawn as blank will be
       elided from the set of characters supported by the font.

       The <rescan> element holds an <int> element which indicates the default
       interval  between  automatic  checks  for  font  configuration changes.
       Fontconfig will validate all of the configuration files and directories
       and  automatically rebuild the internal datastructures when this inter-
       val passes.

       This element is used to black/white list fonts  from  being  listed  or
       matched against.  It holds acceptfont and rejectfont elements.

       Fonts  matched  by  an acceptfont element are "whitelisted"; such fonts
       are explicitly included in the set of fonts used to  resolve  list  and
       match  requests;  including  them in this list protects them from being
       "blacklisted" by a rejectfont  element.   Acceptfont  elements  include
       glob and pattern elements which are used to match fonts.

       Fonts  matched  by  an rejectfont element are "blacklisted"; such fonts
       are excluded from the set of fonts used to resolve list and  match  re-
       quests  as if they didn't exist in the system.  Rejectfont elements in-
       clude glob and pattern elements which are used to match fonts.

       Glob elements hold shell-style filename matching patterns (including  ?
       and  *)  which match fonts based on their complete pathnames.  This can
       be used to exclude a set of  directories  (/usr/share/fonts/uglyfont*),
       or  particular font file types (*.pcf.gz), but the latter mechanism re-
       lies rather heavily on filenaming conventions  which  can't  be  relied
       upon.   Note  that  globs  only apply to directories, not to individual

       Pattern elements perform list-style matching on  incoming  fonts;  that
       is,  they  hold  a  list  of elements and associated values.  If all of
       those elements have a matching value,  then  the  pattern  matches  the
       font.  This can be used to select fonts based on attributes of the font
       (scalable, bold, etc), which is a more reliable  mechanism  than  using
       file extensions.  Pattern elements include patelt elements.

       Patelt elements hold a single pattern element and list of values.  They
       must have a 'name' attribute which indicates the pattern element  name.
       Patelt  elements include int, double, string, matrix, bool, charset and
       const elements.

       This element holds first a (possibly empty) list of <test> elements and
       then  a (possibly empty) list of <edit> elements.  Patterns which match
       all of the tests are subjected to all the edits.  If 'target' is set to
       "font"  instead  of the default "pattern", then this element applies to
       the font name resulting from a match rather than a font pattern  to  be
       matched.  If  'target' is set to "scan", then this element applies when
       the font is scanned to build the fontconfig database.

       This element contains a single value which is compared with the  target
       ('pattern',  'font',  'scan' or 'default') property "property" (substi-
       tute any of the property names seen above). 'compare'  can  be  one  of
       "eq",  "not_eq",  "less",  "less_eq",  "more", "more_eq", "contains" or
       "not_contains".  'qual' may either be the default, "any", in which case
       the  match  succeeds  if any value associated with the property matches
       the test value, or "all", in which case all of  the  values  associated
       with  the  property must match the test value.  'ignore-blanks' takes a
       boolean value. if 'ignore-blanks' is set  "true",  any  blanks  in  the
       string  will be ignored on its comparison. this takes effects only when
       compare="eq" or compare="not_eq".  When used in a <match target="font">
       element,  the  target=  attribute in the <test> element selects between
       matching the original pattern or the font.  "default" selects whichever
       target the outer <match> element has selected.

       This  element  contains a list of expression elements (any of the value
       or operator elements).  The expression elements are evaluated  at  run-
       time  and  modify the property "property".  The modification depends on
       whether "property" was matched by one of  the  associated  <test>  ele-
       ments, if so, the modification may affect the first matched value.  Any
       values inserted into the  property  are  given  the  indicated  binding
       ("strong",  "weak"  or "same") with "same" binding using the value from
       the matched pattern element.  'mode' is one of:

         Mode                    With Match              Without Match
         "assign"                Replace matching value  Replace all values
         "assign_replace"        Replace all values      Replace all values
         "prepend"               Insert before matching  Insert at head of list
         "prepend_first"         Insert at head of list  Insert at head of list
         "append"                Append after matching   Append at end of list
         "append_last"           Append at end of list   Append at end of list
         "delete"                Delete matching value   Delete all values
         "delete_all"            Delete all values       Delete all values

       These elements hold a single value of the indicated type.  <bool>  ele-
       ments hold either true or false.  An important limitation exists in the
       parsing of floating point numbers -- fontconfig requires that the  man-
       tissa start with a digit, not a decimal point, so insert a leading zero
       for purely fractional values (e.g. use 0.5 instead of .5 and  -0.5  in-
       stead of -.5).

       This  element holds four numerical expressions of an affine transforma-
       tion.  At their simplest these will be four <double> elements but  they
       can also be more involved expressions.

       This element holds the two <int> elements of a range representation.

       This  element holds at least one <int> element of an Unicode code point
       or more.

       This element holds at least one <string> element  of  a  RFC-3066-style
       languages or more.

       Holds  a property name.  Evaluates to the first value from the property
       of the pattern.  If the 'target' attribute is not present, it will  de-
       fault  to  'default',  in  which case the property is returned from the
       font pattern during a target="font" match, and to the pattern during  a
       target="pattern"  match.  The attribute can also take the values 'font'
       or 'pattern' to explicitly choose which pattern to use.  It is an error
       to use a target of 'font' in a match that has target="pattern".

       Holds  the  name  of a constant; these are always integers and serve as
       symbolic names for common font values:

         Constant        Property        Value
         thin            weight          0
         extralight      weight          40
         ultralight      weight          40
         light           weight          50
         demilight       weight          55
         semilight       weight          55
         book            weight          75
         regular         weight          80
         normal          weight          80
         medium          weight          100
         demibold        weight          180
         semibold        weight          180
         bold            weight          200
         extrabold       weight          205
         black           weight          210
         heavy           weight          210
         roman           slant           0
         italic          slant           100
         oblique         slant           110
         ultracondensed  width           50
         extracondensed  width           63
         condensed       width           75
         semicondensed   width           87
         normal          width           100
         semiexpanded    width           113
         expanded        width           125
         extraexpanded   width           150
         ultraexpanded   width           200
         proportional    spacing         0
         dual            spacing         90
         mono            spacing         100
         charcell        spacing         110
         unknown         rgba            0
         rgb             rgba            1
         bgr             rgba            2
         vrgb            rgba            3
         vbgr            rgba            4
         none            rgba            5
         lcdnone         lcdfilter       0
         lcddefault      lcdfilter       1
         lcdlight        lcdfilter       2
         lcdlegacy       lcdfilter       3
         hintnone        hintstyle       0
         hintslight      hintstyle       1
         hintmedium      hintstyle       2
         hintfull        hintstyle       3

   <OR>, <AND>, <PLUS>, <MINUS>, <TIMES>, <DIVIDE>
       These elements perform the specified operation on a list of  expression
       elements.  <or> and <and> are boolean, not bitwise.

       These elements compare two values, producing a boolean result.

       Inverts the boolean sense of its one expression element

       This element takes three expression elements; if the value of the first
       is true, it produces the value of the second, otherwise it produces the
       value of the third.

       Alias elements provide a shorthand notation for the set of common match
       operations needed to substitute one font family for another.  They con-
       tain a <family> element followed by  optional  <prefer>,  <accept>  and
       <default>  elements.  Fonts matching the <family> element are edited to
       prepend the list of <prefer>ed families before the  matching  <family>,
       append the <accept>able families after the matching <family> and append
       the <default> families to the end of the family list.

       Holds a single font family name

       These hold a list of <family> elements to be used by the  <alias>  ele-

       This is an example of a system-wide configuration file

       <?xml version="1.0"?>
       <!DOCTYPE fontconfig SYSTEM "fonts.dtd">
       <!-- /etc/fonts/fonts.conf file to configure system font access -->
            Find fonts in these directories

            Accept deprecated 'mono' alias, replacing it with 'monospace'
       <match target="pattern">
            <test qual="any" name="family"><string>mono</string></test>
            <edit name="family" mode="assign"><string>monospace</string></edit>

            Names not including any well known alias are given 'sans-serif'
       <match target="pattern">
            <test qual="all" name="family" compare="not_eq"><string>sans-serif</string></test>
            <test qual="all" name="family" compare="not_eq"><string>serif</string></test>
            <test qual="all" name="family" compare="not_eq"><string>monospace</string></test>
            <edit name="family" mode="append_last"><string>sans-serif</string></edit>

            Load per-user customization file, but don't complain
            if it doesn't exist
       <include ignore_missing="yes" prefix="xdg">fontconfig/fonts.conf</include>

            Load local customization files, but don't complain
            if there aren't any
       <include ignore_missing="yes">conf.d</include>
       <include ignore_missing="yes">local.conf</include>

            Alias well known font names to available TrueType fonts.
            These substitute TrueType faces for similar Type1
            faces to improve screen appearance.
            <prefer><family>Times New Roman</family></prefer>
            <prefer><family>Courier New</family></prefer>

            Provide required aliases for standard names
            Do these after the users configuration file so that
            any aliases there are used preferentially
            <prefer><family>Times New Roman</family></prefer>
            <prefer><family>Andale Mono</family></prefer>

            The example of the requirements of OR operator;
            If the 'family' contains 'Courier New' OR 'Courier'
            add 'monospace' as the alternative
       <match target="pattern">
            <test name="family" compare="eq">
                 <string>Courier New</string>
            <edit name="family" mode="prepend">
       <match target="pattern">
            <test name="family" compare="eq">
            <edit name="family" mode="prepend">


       This  is  an  example  of  a  per-user configuration file that lives in

       <?xml version="1.0"?>
       <!DOCTYPE fontconfig SYSTEM "fonts.dtd">
       <!-- $XDG_CONFIG_HOME/fontconfig/fonts.conf for per-user font configuration -->

            Private font directory
       <dir prefix="xdg">fonts</dir>

            use rgb sub-pixel ordering to improve glyph appearance on
            LCD screens.  Changes affecting rendering, but not matching
            should always use target="font".
       <match target="font">
            <edit name="rgba" mode="assign"><const>rgb</const></edit>
            use WenQuanYi Zen Hei font when serif is requested for Chinese
                 If you don't want to use WenQuanYi Zen Hei font for zh-tw etc,
                 you can use zh-cn instead of zh.
                 Please note, even if you set zh-cn, it still matches zh.
                 if you don't like it, you can use compare="eq"
                 instead of compare="contains".
            <test name="lang" compare="contains">

            <test name="family">
            <edit name="family" mode="prepend">
                 <string>WenQuanYi Zen Hei</string>
            use VL Gothic font when sans-serif is requested for Japanese
            <test name="lang" compare="contains">
            <test name="family">
            <edit name="family" mode="prepend">
                 <string>VL Gothic</string>

       fonts.conf contains configuration information for  the  fontconfig  li-
       brary consisting of directories to look at for font information as well
       as instructions on editing program specified font patterns  before  at-
       tempting to match the available fonts.  It is in XML format.

       conf.d  is the conventional name for a directory of additional configu-
       ration files managed by external applications or the local  administra-
       tor.   The filenames starting with decimal digits are sorted in lexico-
       graphic order and used as additional configuration files.  All of these
       files  are  in  XML format.  The master fonts.conf file references this
       directory in an <include> directive.

       fonts.dtd is a DTD that  describes  the  format  of  the  configuration

       $XDG_CONFIG_HOME/fontconfig/conf.d  and  ~/.fonts.conf.d is the conven-
       tional name for a per-user directory of (typically auto-generated) con-
       figuration  files,  although  the  actual  location is specified in the
       global fonts.conf file. please note that ~/.fonts.conf.d is  deprecated
       now. it will not be read by default in the future version.

       $XDG_CONFIG_HOME/fontconfig/fonts.conf and ~/.fonts.conf is the conven-
       tional location for per-user font configuration,  although  the  actual
       location  is  specified in the global fonts.conf file. please note that
       ~/.fonts.conf is deprecated now. it will not be read by default in  the
       future version.

       $XDG_CACHE_HOME/fontconfig/*.cache-*  and   ~/.fontconfig/*.cache-*  is
       the conventional repository of font information that isn't found in the
       per-directory  caches.   This file is automatically maintained by font-
       config. please note that ~/.fontconfig/*.cache-* is deprecated now.  it
       will not be read by default in the future version.

       FONTCONFIG_FILE is used to override the default configuration file.

       FONTCONFIG_PATH  is  used  to override the default configuration direc-

       FONTCONFIG_SYSROOT is used to set a default sysroot directory.

       FC_DEBUG is used to output the detailed debugging messages. see  Debug-
       ging Applications section for more details.

       FC_DBG_MATCH_FILTER  is  used  to filter out the patterns. this takes a
       comma-separated list of object names and effects only when FC_DEBUG has
       MATCH2. see Debugging Applications section for more details.

       FC_LANG  is used to specify the default language as the weak binding in
       the query. if this isn't set, the default language will  be  determined
       from current locale.

       FONTCONFIG_USE_MMAP is used to control the use of mmap(2) for the cache
       files if available. this take a boolean value. fontconfig  will  checks
       if  the  cache  files  are stored on the filesystem that is safe to use
       mmap(2). explicitly setting this environment variable will causes skip-
       ping this check and enforce to use or not use mmap(2) anyway.

       SOURCE_DATE_EPOCH  is  used  to ensure fc-cache(1) generates files in a
       deterministic manner in order to support reproducible builds. When  set
       to  a  numeric representation of UNIX timestamp, fontconfig will prefer
       this value over using the modification timestamps of the input files in
       order   to   identify   which  cache  files  require  regeneration.  If
       SOURCE_DATE_EPOCH is not set (or is newer than the mtime of the  direc-
       tory), the existing behaviour is unchanged.

       fc-cat(1),    fc-cache(1),    fc-list(1),   fc-match(1),   fc-query(1),

       Fontconfig version 2.13.1

                                 06 April 2020                   FONTS-CONF(5)
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