gperl(1) — Linux manual page

Name | Synopsis | Description | Options | Perl Parts | Example | Authors | See Also | COLOPHON

gperl(1)                   General Commands Manual                  gperl(1)

Name         top

       gperl - groff preprocessor for Perl parts in roff files

Synopsis         top

       gperl [filespec ...]

       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.

Options         top

       So far, there are only filespec or breaking options.

       filespec are file names or the minus character - character for
       standard input.  As usual, the argument -- can be used in order to
       let all following arguments mean file names, even if the names begin
       with a minus character -.

       An option is breaking, when the program just writes the information
       that was asked for and then stops.  All other arguments will be
       ignored by that.  These breaking options are here

       -h | --help
              Print help information with a short explanation of options to
              standard output.

       -v | --version
              Print version information to standard output.

Perl Parts         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 number 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 number 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 number registers
       can be very restrictive.

       In string mode, gperl generates a groff string storage line
              .ds var_name content
       In number 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 number 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 number register and the second as
              string by
              .nr var_name1 output_line1
              .ds var_name2 output_line2

   Printing towards STDERR is without storage
       The printing towards STDERR, (standard error) works as usual.  All
       error information goes to the real normal standard error, without
       other automatic storage.

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 created:
              .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 2020-07-14.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-07-12.)  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            16 May 2020                        gperl(1)