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refer(1)                    General Commands Manual                   refer(1)


       refer - process bibliographic references for groff


       refer [-bCenPRS] [-a n] [-B field.macro] [-c fields] [-f n] [-i fields]
             [-k field] [-l range-expression] [-p database-file] [-s fields]
             [-t n] [file ...]

       refer --help

       refer -v
       refer --version


       The GNU implementation of refer is part of the groff(1) document
       formatting system.  refer is a troff(1) preprocessor that prepares
       bibilographic citations by looking up keywords specified in a roff(7)
       input document, obviating the need to type such annotations, and
       permitting the citation style in formatted output to be altered
       independently and systematically.  It copies the contents of each file
       to the standard output stream, except that it interprets lines between
       .[ and .] as citations to be translated into groff input, and lines
       between .R1 and .R2 as instructions regarding how citations are to be
       processed.  Normally, refer is not executed directly by the user, but
       invoked by specifying the -R option to groff(1).  If no file operands
       are given on the command line, or if file is "-", the standard input
       stream is read.

       Each citation specifies a reference.  The citation can specify a
       reference that is contained in a bibliographic database by giving a set
       of keywords that only that reference contains.  Alternatively it can
       specify a reference by supplying a database record in the citation.  A
       combination of these alternatives is also possible.

       For each citation, refer can produce a mark in the text.  This mark
       consists of some label which can be separated from the text and from
       other labels in various ways.  For each reference it also outputs
       groff(7) language commands that can be used by a macro package to
       produce a formatted reference for each citation.  The output of refer
       must therefore be processed using a suitable macro package, such as me,
       mm, mom, or ms.  The commands to format a citation's reference can be
       output immediately after the citation, or the references may be
       accumulated, and the commands output at some later point.  If the
       references are accumulated, then multiple citations of the same
       reference will produce a single formatted reference.

       The interpretation of lines between .R1 and .R2 as prepreocessor
       commands is a feature of GNU refer.  Documents making use of this
       feature can still be processed by AT&T refer just by adding the lines
              .de R1
              .ig R2
       to the beginning of the document.  This will cause troff(1) to ignore
       everything between .R1 and .R2.  The effect of some commands can also
       be achieved by options.  These options are supported mainly for
       compatibility with AT&T refer.  It is usually more convenient to use

       refer generates .lf requests so that file names and line numbers in
       messages produced by commands that read refer output will be correct;
       it also interprets lines beginning with .lf so that file names and line
       numbers in the messages and .lf lines that it produces will be accurate
       even if the input has been preprocessed by a command such as soelim(1).

   Bibliographic databases
       The bibliographic database is a text file consisting of records
       separated by one or more blank lines.  Within each record fields start
       with a % at the beginning of a line.  Each field has a one character
       name that immediately follows the %.  It is best to use only upper and
       lower case letters for the names of fields.  The name of the field
       should be followed by exactly one space, and then by the contents of
       the field.  Empty fields are ignored.  The conventional meaning of each
       field is as follows:

       %A     The name of an author.  If the name contains a suffix such as
              "Jr.", it should be separated from the last name by a comma.
              There can be multiple occurrences of the %A field.  The order is
              significant.  It is a good idea always to supply an %A field or
              a %Q field.

       %B     For an article that is part of a book, the title of the book.

       %C     The place (city) of publication.

       %D     The date of publication.  The year should be specified in full.
              If the month is specified, the name rather than the number of
              the month should be used, but only the first three letters are
              required.  It is a good idea always to supply a %D field; if the
              date is unknown, a value such as in press or unknown can be

       %E     For an article that is part of a book, the name of an editor of
              the book.  Where the work has editors and no authors, the names
              of the editors should be given as %A fields and ", (ed.)" or
              ", (eds.)" should be appended to the last author.

       %G     U.S. government ordering number.

       %I     The publisher (issuer).

       %J     For an article in a journal, the name of the journal.

       %K     Keywords to be used for searching.

       %L     Label.

       %N     Journal issue number.

       %O     Other information.  This is usually printed at the end of the

       %P     Page number.  A range of pages can be specified as m-n.

       %Q     The name of the author, if the author is not a person.  This
              will only be used if there are no %A fields.  There can only be
              one %Q field.

       %R     Technical report number.

       %S     Series name.

       %T     Title.  For an article in a book or journal, this should be the
              title of the article.

       %V     Volume number of the journal or book.

       %X     Annotation.

       For all fields except %A and %E, if there is more than one occurrence
       of a particular field in a record, only the last such field will be

       If accent strings are used, they should follow the character to be
       accented.  This means that an ms document must call the .AM macro when
       it initializes.  Accent strings should not be quoted: use one \ rather
       than two.  Accent strings are an obsolescent feature of the me and ms
       macro packages; modern documents should use groff special character
       escape sequences instead; see groff_char(7).

       Citations have a characteristic format.
              flags keywords

       The opening-text, closing-text, and flags components are optional.
       Only one of the keywords and fields components need be specified.

       The keywords component says to search the bibliographic databases for a
       reference that contains all the words in keywords.  It is an error if
       more than one reference is found.

       The fields components specifies additional fields to replace or
       supplement those specified in the reference.  When references are being
       accumulated and the keywords component is non-empty, then additional
       fields should be specified only on the first occasion that a particular
       reference is cited, and will apply to all citations of that reference.

       The opening-text and closing-text components specify strings to be used
       to bracket the label instead of those in the bracket-label command.  If
       either of these components is non-empty, the strings specified in the
       bracket-label command will not be used; this behavior can be altered
       using the [ and ] flags.  Leading and trailing spaces are significant
       for these components.

       The flags component is a list of non-alphanumeric characters each of
       which modifies the treatment of this particular citation.  AT&T refer
       will treat these flags as part of the keywords and so will ignore them
       since they are non-alphanumeric.  The following flags are currently

       #      Use the label specified by the short-label command, instead of
              that specified by the label command.  If no short label has been
              specified, the normal label will be used.  Typically the short
              label is used with author-date labels and consists of only the
              date and possibly a disambiguating letter; the "#" is supposed
              to be suggestive of a numeric type of label.

       [      Precede opening-text with the first string specified in the
              bracket-label command.

       ]      Follow closing-text with the second string specified in the
              bracket-label command.

       An advantage of using the [ and ] flags rather than including the
       brackets in opening-text and closing-text is that you can change the
       style of bracket used in the document just by changing the
       bracket-label command.  Another is that sorting and merging of
       citations will not necessarily be inhibited if the flags are used.

       If a label is to be inserted into the text, it will be attached to the
       line preceding the .[ line.  If there is no such line, then an extra
       line will be inserted before the .[ line and a warning will be given.

       There is no special notation for making a citation to multiple
       references.  Just use a sequence of citations, one for each reference.
       Don't put anything between the citations.  The labels for all the
       citations will be attached to the line preceding the first citation.
       The labels may also be sorted or merged.  See the description of the <>
       label expression, and of the sort-adjacent-labels and
       abbreviate-label-ranges commands.  A label will not be merged if its
       citation has a non-empty opening-text or closing-text.  However, the
       labels for a citation using the ] flag and without any closing-text
       immediately followed by a citation using the [ flag and without any
       opening-text may be sorted and merged even though the first citation's
       opening-text or the second citation's closing-text is non-empty.  (If
       you wish to prevent this, use the dummy character escape sequence \& as
       the first citation's closing-text.)

       Commands are contained between lines starting with .R1 and .R2.
       Recognition of these lines can be prevented by the -R option.  When a
       .R1 line is recognized any accumulated references are flushed out.
       Neither .R1 nor .R2 lines, nor anything between them, is output.

       Commands are separated by newlines or semicolons.  A number sign (#)
       introduces a comment that extends to the end of the line, but does not
       conceal the newline.  Each command is broken up into words.  Words are
       separated by spaces or tabs.  A word that begins with a (neutral)
       double quote (") extends to the next double quote that is not followed
       by another double quote.  If there is no such double quote, the word
       extends to the end of the line.  Pairs of double quotes in a word
       beginning with a double quote collapse to one double quote.  Neither a
       number sign nor a semicolon is recognized inside double quotes.  A line
       can be continued by ending it with a backslash "\"; this works
       everywhere except after a number sign.

       Each command name that is marked with * has an associated negative
       command no-name that undoes the effect of name.  For example, the
       no-sort command specifies that references should not be sorted.  The
       negative commands take no arguments.

       In the following description each argument must be a single word; field
       is used for a single upper or lower case letter naming a field; fields
       is used for a sequence of such letters; m and n are used for a non-
       negative numbers; string is used for an arbitrary string; file is used
       for the name of a file.

       abbreviate* fields string1 string2 string3 string4
              Abbreviate the first names of fields.  An initial letter will be
              separated from another initial letter by string1, from the last
              name by string2, and from anything else (such as "von" or "de")
              by string3.  These default to a period followed by a space.  In
              a hyphenated first name, the initial of the first part of the
              name will be separated from the hyphen by string4; this defaults
              to a period.  No attempt is made to handle any ambiguities that
              might result from abbreviation.  Names are abbreviated before
              sorting and before label construction.

       abbreviate-label-ranges* string
              Three or more adjacent labels that refer to consecutive
              references will be abbreviated to a label consisting of the
              first label, followed by string, followed by the last label.
              This is mainly useful with numeric labels.  If string is
              omitted, it defaults to "-".

              Accumulate references instead of writing out each reference as
              it is encountered.  Accumulated references will be written out
              whenever a reference of the form
              is encountered, after all input files have been processed, and
              whenever a .R1 line is recognized.

       annotate* field string
              field is an annotation; print it at the end of the reference as
              a paragraph preceded by the line


              If string is omitted, it will default to AP; if field is also
              omitted it will default to X.  Only one field can be an

       articles string ...
              Each string is a definite or indefinite article, and should be
              ignored at the beginning of T fields when sorting.  Initially,
              "a", "an", and "the" are recognized as articles.

       bibliography file ...
              Write out all the references contained in each bibliographic
              database file.  This command should come last in an .R1/.R2

       bracket-label string1 string2 string3
              In the text, bracket each label with string1 and string2.  An
              occurrence of string2 immediately followed by string1 will be
              turned into string3.  The default behavior is as follows.
                     bracket-label \*([. \*(.] ", "

       capitalize fields
              Convert fields to caps and small caps.

              Recognize .R1 and .R2 even when followed by a character other
              than space or newline.

       database file ...
              Search each bibliographic database file.  For each file, if an
              index file.i created by indxbib(1) exists, then it will be
              searched instead; each index can cover multiple databases.

       date-as-label* string
              string is a label expression that specifies a string with which
              to replace the D field after constructing the label.  See
              subsection "Label expressions" below for a description of label
              expressions.  This command is useful if you do not want explicit
              labels in the reference list, but instead want to handle any
              necessary disambiguation by qualifying the date in some way.
              The label used in the text would typically be some combination
              of the author and date.  In most cases you should also use the
              no-label-in-reference command.  For example,
                     date-as-label D.+yD.y%a*D.-y
              would attach a disambiguating letter to the year part of the D
              field in the reference.

              The default database should be searched.  This is the default
              behavior, so the negative version of this command is more
              useful.  refer determines whether the default database should be
              searched on the first occasion that it needs to do a search.
              Thus a no-default-database command must be given before then, in
              order to be effective.

       discard* fields
              When the reference is read, fields should be discarded; no
              string definitions for fields will be output.  Initially, fields
              are XYZ.

       et-al* string m n
              Control use of et al. in the evaluation of @ expressions in
              label expressions.  If the number of authors needed to make the
              author sequence unambiguous is u and the total number of authors
              is t then the last t-u authors will be replaced by string
              provided that t-u is not less than m and t is not less than n.
              The default behavior is as follows.
                     et-al " et al" 2 3
              Note the absence of a dot from the end of the abbreviation,
              which is arguably not correct.  (Et al[.] is short for et alli,
              as etc. is short for et cetera.)

       include file
              Include file and interpret the contents as commands.

       join-authors string1 string2 string3
              Join multiple authors together with strings.  When there are
              exactly two authors, they will be joined with string1.  When
              there are more than two authors, all but the last two will be
              joined with string2, and the last two authors will be joined
              with string3.  If string3 is omitted, it will default to
              string1; if string2 is also omitted it will also default to
              string1.  For example,
                     join-authors " and " ", " ", and "
              will restore the default method for joining authors.

              When outputting the reference, define the string [F to be the
              reference's label.  This is the default behavior, so the
              negative version of this command is more useful.

              For each reference output a label in the text.  The label will
              be separated from the surrounding text as described in the
              bracket-label command.  This is the default behavior, so the
              negative version of this command is more useful.

       label string
              string is a label expression describing how to label each

       separate-label-second-parts string
              When merging two-part labels, separate the second part of the
              second label from the first label with string.  See the
              description of the <> label expression.

              In the text, move any punctuation at the end of line past the
              label.  It is usually a good idea to give this command unless
              you are using superscripted numbers as labels.

       reverse* string
              Reverse the fields whose names are in string.  Each field name
              can be followed by a number which says how many such fields
              should be reversed.  If no number is given for a field, all such
              fields will be reversed.

       search-ignore* fields
              While searching for keys in databases for which no index exists,
              ignore the contents of fields.  Initially, fields XYZ are

       search-truncate* n
              Only require the first n characters of keys to be given.  In
              effect when searching for a given key words in the database are
              truncated to the maximum of n and the length of the key.
              Initially, n is 6.

       short-label* string
              string is a label expression that specifies an alternative
              (usually shorter) style of label.  This is used when the # flag
              is given in the citation.  When using author-date style labels,
              the identity of the author or authors is sometimes clear from
              the context, and so it may be desirable to omit the author or
              authors from the label.  The short-label command will typically
              be used to specify a label containing just a date and possibly a
              disambiguating letter.

       sort* string
              Sort references according to string.  References will
              automatically be accumulated.  string should be a list of field
              names, each followed by a number, indicating how many fields
              with the name should be used for sorting.  "+" can be used to
              indicate that all the fields with the name should be used.  Also
              . can be used to indicate the references should be sorted using
              the (tentative) label.  (Subsection "Label expressions" below
              describes the concept of a tentative label.)

              Sort labels that are adjacent in the text according to their
              position in the reference list.  This command should usually be
              given if the abbreviate-label-ranges command has been given, or
              if the label expression contains a <> expression.  This will
              have no effect unless references are being accumulated.

   Label expressions
       Label expressions can be evaluated both normally and tentatively.  The
       result of normal evaluation is used for output.  The result of
       tentative evaluation, called the tentative label, is used to gather the
       information that normal evaluation needs to disambiguate the label.
       Label expressions specified by the date-as-label and short-label
       commands are not evaluated tentatively.  Normal and tentative
       evaluation are the same for all types of expression other than @, *,
       and % expressions.  The description below applies to normal evaluation,
       except where otherwise specified.

       field n
              The n-th part of field.  If n is omitted, it defaults to 1.

              The characters in string literally.

       @      All the authors joined as specified by the join-authors command.
              The whole of each author's name will be used.  However, if the
              references are sorted by author (that is, the sort specification
              starts with "A+"), then authors' last names will be used
              instead, provided that this does not introduce ambiguity, and
              also an initial subsequence of the authors may be used instead
              of all the authors, again provided that this does not introduce
              ambiguity.  The use of only the last name for the i-th author of
              some reference is considered to be ambiguous if there is some
              other reference, such that the first i-1 authors of the
              references are the same, the i-th authors are not the same, but
              the i-th authors last names are the same.  A proper initial
              subsequence of the sequence of authors for some reference is
              considered to be ambiguous if there is a reference with some
              other sequence of authors which also has that subsequence as a
              proper initial subsequence.  When an initial subsequence of
              authors is used, the remaining authors are replaced by the
              string specified by the et-al command; this command may also
              specify additional requirements that must be met before an
              initial subsequence can be used.  @ tentatively evaluates to a
              canonical representation of the authors, such that authors that
              compare equally for sorting purpose will have the same

       %I     The serial number of the reference formatted according to the
              character following the %.  The serial number of a reference
              is 1 plus the number of earlier references with same tentative
              label as this reference.  These expressions tentatively evaluate
              to an empty string.

       expr*  If there is another reference with the same tentative label as
              this reference, then expr, otherwise an empty string.  It
              tentatively evaluates to an empty string.

       expr-n The first (+) or last (-) n upper or lower case letters or
              digits of expr.  roff special characters (such as \('a) count as
              a single letter.  Accent strings are retained but do not count
              towards the total.

       expr.l expr converted to lowercase.

       expr.u expr converted to uppercase.

       expr.c expr converted to caps and small caps.

       expr.r expr reversed so that the last name is first.

       expr.a expr with first names abbreviated.  Fields specified in the
              abbreviate command are abbreviated before any labels are
              evaluated.  Thus .a is useful only when you want a field to be
              abbreviated in a label but not in a reference.

       expr.y The year part of expr.

              The part of expr before the year, or the whole of expr if it
              does not contain a year.

              The part of expr after the year, or an empty string if expr does
              not contain a year.

       expr.n The last name part of expr.

              expr1 except that if the last character of expr1 is - then it
              will be replaced by expr2.

       expr1 expr2
              The concatenation of expr1 and expr2.

              If expr1 is non-empty then expr1 otherwise expr2.

              If expr1 is non-empty then expr2 otherwise an empty string.

              If expr1 is non-empty then expr2 otherwise expr3.

       <expr> The label is in two parts, which are separated by expr.  Two
              adjacent two-part labels which have the same first part will be
              merged by appending the second part of the second label onto the
              first label separated by the string specified in the
              separate-label-second-parts command (initially, a comma followed
              by a space); the resulting label will also be a two-part label
              with the same first part as before merging, and so additional
              labels can be merged into it.  It is permissible for the first
              part to be empty; this may be desirable for expressions used in
              the short-label command.

       (expr) The same as expr.  Used for grouping.

       The above expressions are listed in order of precedence (highest
       first); & and | have the same precedence.

   Macro interface
       Each reference starts with a call to the macro ]-.  The string [F will
       be defined to be the label for this reference, unless the
       no-label-in-reference command has been given.  There then follows a
       series of string definitions, one for each field: string [X corresponds
       to field X.  The register [P is set to 1 if the P field contains a
       range of pages.  The [T, [A and [O registers are set to 1 according as
       the T, A and O fields end with any of .?! (an end-of-sentence
       character).  The [E register will be set to 1 if the [E string contains
       more than one name.  The reference is followed by a call to the ][
       macro.  The first argument to this macro gives a number representing
       the type of the reference.  If a reference contains a J field, it will
       be classified as type 1, otherwise if it contains a B field, it will be
       type 3, otherwise if it contains a G or R field it will be type 4,
       otherwise if it contains an I field it will be type 2, otherwise it
       will be type 0.  The second argument is a symbolic name for the type:
       other, journal-article, book, article-in-book, or tech-report.  Groups
       of references that have been accumulated or are produced by the
       bibliography command are preceded by a call to the ]< macro and
       followed by a call to the ]> macro.


       --help displays a usage message, while -v and --version show version
       information; all exit afterward.

       -R     Don't recognize lines beginning with .R1/.R2.

       Other options are equivalent to refer commands.

       -a n            reverse An

       -b              no-label-in-text; no-label-in-reference

       -B              See below.

       -c fields       capitalize fields

       -C              compatible

       -e              accumulate

       -f n            label %n

       -i fields       search-ignore fields

       -k              label L~%a

       -k field        label field~%a

       -l              label A.nD.y%a

       -l m            label A.n+mD.y%a

       -l ,n           label A.nD.y-n%a

       -l m,n          label A.n+mD.y-n%a

       -n              no-default-database

       -p db-file      database db-file

       -P              move-punctuation

       -s spec         sort spec

       -S              label "(A.n|Q) ', ' (D.y|D)"; bracket-label " (" ) "; "

       -t n            search-truncate n

       The B option has command equivalents with the addition that the file
       names specified on the command line are processed as if they were
       arguments to the bibliography command instead of in the normal way.

       -B              annotate X AP; no-label-in-reference

       -B field.macro  annotate field macro; no-label-in-reference


       REFER  If set, overrides the default database.


              Default database.

       file.i Index files.

              defines macros and strings facilitating integration with macro
              packages that wish to support refer.

       refer uses temporary files.  See the groff(1) man page for details of
       where such files are created.


       In label expressions, <> expressions are ignored inside .char


       We can illustrate the operation of refer with a sample bibliographic
       database containing one entry and a simple roff document to cite that

              $ cat > my-db-file
              %A Daniel P.\& Friedman
              %A Matthias Felleisen
              %C Cambridge, Massachusetts
              %D 1996
              %I The MIT Press
              %T The Little Schemer, Fourth Edition
              $ refer -p my-db-file
              Read the book
              on your summer vacation.
              .lf 1 -
              Read the book\*([.1\*(.]
              .ds [F 1
              .ds [A Daniel P. Friedman and Matthias Felleisen
              .ds [C Cambridge, Massachusetts
              .ds [D 1996
              .ds [I The MIT Press
              .ds [T The Little Schemer, Fourth Edition
              .nr [T 0
              .nr [A 0
              .][ 2 book
              .lf 5 -
              on your summer vacation.

       The foregoing shows us that refer (a) produces a label "1"; (b)
       brackets that label with interpolations of the "[." and ".]" strings;
       (c) calls a macro "]-"; (d) defines strings and registers containing
       the label and bibliographic data for the reference; (e) calls a macro
       "]["; and (f) uses the lf request to restore the line numbers of the
       original input.  As discussed in subsection "Macro interface" above, it
       is up to the document or a macro package to employ and format this
       information usefully.  Let us see how we might turn groff_ms(7) to this

              $ REFER=my-db-file groff -R -ms
              Read the book
              on your summer vacation.
              Commentary is available.\*{*\*}
              .FS \*{*\*}
              Space reserved for penetrating insight.

       ms's automatic footnote numbering mechanism is not aware of refer's
       label numbering, so we have manually specified a (superscripted)
       symbolic footnote for our non-bibliographic aside.

See also

       "Some Applications of Inverted Indexes on the Unix System", by M. E.
       Lesk, 1978, AT&T Bell Laboratories Computing Science Technical Report
       No. 69.

       indxbib(1), lookbib(1), lkbib(1)

groff 1.23.0                      2 July 2023                         refer(1)

groff 1.23.0 - Generated Sat Dec 23 06:20:35 CST 2023
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