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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 commands.
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 used.
%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 reference.
%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 used.
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
Citations have a characteristic format.
.[opening-text
flags keywords
fields
.]closing-text
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 recognized.
# 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
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*
Accumulate references instead of writing out each reference
as it is encountered. Accumulated references will be
written out whenever a reference of the form
.[
$LIST$
.]
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
.string
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 annotation.
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 block.
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.
compatible*
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.
default-database*
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.
label-in-reference*
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.
label-in-text*
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
reference.
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.
move-punctuation*
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 ignored.
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-adjacent-labels*
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
field n
The n-th part of field. If n is omitted, it defaults to 1.
'string'
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
representation.
%n
%a
%A
%i
%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
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.
expr.+y
The part of expr before the year, or the whole of expr if
it does not contain a year.
expr.-y
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~expr2
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.
expr1|expr2
If expr1 is non-empty then expr1 otherwise expr2.
expr1&expr2
If expr1 is non-empty then expr2 otherwise an empty string.
expr1?expr2:expr3
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.
/usr/dict/papers/Ind
Default database.
file.i Index files.
/usr/local/share/groff/1.23.0/tmac/refer.tmac
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
expressions.
We can illustrate the operation of refer with a sample
bibliographic database containing one entry and a simple roff
document to cite that entry.
$ 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
.[
friedman
.]
on your summer vacation.
<Control+D>
.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 task.
$ REFER=my-db-file groff -R -ms
.LP
Read the book
.[
friedman
.]
on your summer vacation.
Commentary is available.\*{*\*}
.FS \*{*\*}
Space reserved for penetrating insight.
.FE
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.
“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)
This page is part of the groff (GNU troff) project. Information
about the project can be found at
⟨http://www.gnu.org/software/groff/⟩. If you have a bug report for
this manual page, see ⟨http://www.gnu.org/software/groff/⟩. This
page was obtained from the tarball groff-1.23.0.tar.gz fetched
from ⟨https://ftp.gnu.org/gnu/groff/⟩ on 2026-01-16. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
groff 1.23.0 2 July 2023 refer(1)
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