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gperl(1)                    General Commands Manual                   gperl(1)


Name

       gperl - execute Perl commands in groff documents


Synopsis

       gperl [file ...]

       gperl -h
       gperl --help

       gperl -v
       gperl --version


Description

       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

       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.

              o      .Perl

              o      .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.

              o      .Perl stop

              o      .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
              and
                     .Perl .ds var_name1 .ds var_name2

       .Perl .nr var_name1 varname2
              stores both variables as register variables.  gperl generates
              .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

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

       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

       gperl was written by Bernd Warken <groff-bernd.warken-72@web.de>.


See also

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

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

groff 1.23.0                      2 July 2023                         gperl(1)

groff 1.23.0 - Generated Sat Dec 23 06:21:17 CST 2023
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