gperl(1) — Linux manual page

Name | Synopsis | Description | Perl regions | Example | Authors | See also | COLOPHON

gperl(1)                 General Commands Manual                gperl(1)

Name         top

       gperl - execute Perl commands in groff documents

Synopsis         top

       gperl [file ...]

       gperl -h
       gperl --help

       gperl -v
       gperl --version

Description         top

       This is a preprocessor for groff(1).  It allows the use of
       perl(7) code in groff(7) files.  The result of a Perl part can be
       stored in groff strings or numerical registers based on the
       arguments at a final line of a Perl part.

       If no operands are given, or if file is “-”, gperl reads the
       standard input stream.  A double-dash argument (“--”) causes all
       subsequent arguments to be interpreted as file operands, even if
       their names start with a dash.  -h and --help display a usage
       message, whereas -v and --version display version information;
       all exit afterward.

Perl regions         top

       Perl parts in groff files are enclosed by two .Perl requests with
       different arguments, a starting and an ending command.

   Starting Perl mode
       The starting Perl request can either be without arguments, or by
       a request that has the term start as its only argument.

              •      .Perl.Perl start

   Ending Perl mode without storage
       A .Perl command line with an argument different from start
       finishes a running Perl part.  Of course, it would be reasonable
       to add the argument stop; that's possible, but not necessary.

              •      .Perl stop.Perl other_than_start
       The argument other_than_start can additionally be used as a groff
       string variable name for storage — see next section.

   Ending Perl mode with storage
       A useful feature of gperl is to store one or more results from
       the Perl mode.

       The output of a Perl part can be got with backticks `...`.

       This program collects all printing to STDOUT (normal standard
       output) by the Perl print program.  This pseudo-printing output
       can have several lines, due to printed line breaks with \n.  By
       that, the output of a Perl run should be stored into a Perl
       array, with a single line for each array member.

       This Perl array output can be stored by gperl in either

       groff strings
              by creating a groff command .ds

       groff register
              by creating a groff command .rn

       The storage modes can be determined by arguments of a final
       stopping .Perl command.  Each argument .ds changes the mode into
       groff string and .nr changes the mode into groff register for all
       following output parts.

       By default, all output is saved as strings, so .ds is not really
       needed before the first .nr command.  That suits to groff(7),
       because every output can be saved as groff string, but the
       registers can be very restrictive.

       In string mode, gperl generates a groff string storage line
              .ds var_name content
       In register mode the following groff command is generated
              .nr var_name content

       We present argument collections in the following.  You can add as
       first argument for all stop.  We omit this additional element.

       .Perl .ds var_name
              This will store 1 output line into the groff string named
              var_name by the automatically created command
                     .ds var_name output

       .Perl var_name
              If var_name is different from start this is equivalent to
              the former command, because the string mode is string with
              .ds command.  default.

       .Perl var_name1 var_name2
              This will store 2 output lines into groff string names
              var_name1 and var_name2, because the default mode .ds is
              active, such that no .ds argument is needed.  Of course,
              this is equivalent to
                     .Perl .ds var_name1 var_name2
                     .Perl .ds var_name1 .ds var_name2

       .Perl .nr var_name1 varname2
              stores both variables as register variables.  gperl
              .nr var_name1 output_line1
              .nr var_name2 output_line2

       .Perl .nr var_name1 .ds var_name2
              stores the 1st argument as register and the second as
              string by
              .nr var_name1 output_line1
              .ds var_name2 output_line2

Example         top

       A possible Perl part in a roff file could look like that:
              .Perl start
              my $result = 'some data';
              print $result;
              .Perl stop .ds string_var

       This stores the result ”some data” into the roff string called
       string_var, such that the following line is printed:
              .ds string_var some data
       by gperl as food for the coming groff run.

       A Perl part with several outputs is:
              .Perl start
              print ”first\n”;
              print ”second line\n”;
              print ”3\n”;
              .Perl var1 var2 .nr var3
       This stores 3 printed lines into 3 groff strings.
       var1,var2,var3.  So the following groff command lines are
              .ds var1 first
              .ds var2 second line
              .nr var3 3

Authors         top

       gperl was written by Bernd Warken ⟨⟩.

See also         top

       Man pages related to groff are groff(1), groff(7), and grog(1).

       Documents related to Perl are perl(1), perl(7).

COLOPHON         top

       This page is part of the groff (GNU troff) project.  Information
       about the project can be found at 
       ⟨⟩.  If you have a bug report
       for this manual page, see ⟨⟩.
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-08.)  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

groff 1 November 2023                    gperl(1)