News::Newsrc - manage newsrc files

NAME

News::Newsrc - manage newsrc files

SUPPORTED PLATFORMS

This module is not included with the standard ActivePerl distribution. It is available as a separate download using PPM.

SYNOPSIS

  use News::Newsrc;


  $newsrc   = new News::Newsrc;

  $ok       = $newsrc->load;
  $ok       = $newsrc->load             ($file);
              $newsrc->import_rc        ( @lines);
              $newsrc->import_rc        (\@lines);

              $newsrc->save;
              $newsrc->save_as          ($file);
  @lines    = $newsrc->export_rc;

  $ok       = $newsrc-> add_group       ($group,             %options);
  $ok       = $newsrc->move_group       ($group,             %options);
  $ok       = $newsrc-> del_group       ($group);

              $newsrc->  subscribe      ($group,             %options);
              $newsrc->unsubscribe      ($group,             %options);

              $newsrc->mark             ($group,  $article , %options);
              $newsrc->mark_list        ($group, \@articles, %options);
              $newsrc->mark_range       ($group, $from, $to, %options);

              $newsrc->unmark           ($group,  $article , %options);
              $newsrc->unmark_list      ($group, \@articles, %options);
              $newsrc->unmark_range     ($group, $from, $to, %options);

       ... if $newsrc->exists           ($group);
       ... if $newsrc->subscribed       ($group);
       ... if $newsrc->marked           ($group, $article);

  $n        = $newsrc->  num_groups;
  @groups   = $newsrc->      groups;
  @groups   = $newsrc->  sub_groups;
  @groups   = $newsrc->unsub_groups;

  @articles = $newsrc->  marked_articles($group,             %options);
  @articles = $newsrc->unmarked_articles($group, $from, $to, %options);

  $articles = $newsrc->get_articles     ($group,             %options);
  $ok       = $newsrc->set_articles     ($group, $articles,  %options);

REQUIRES

Perl 5.004, Set::IntSpan 1.07

EXPORTS

Nothing

DESCRIPTION

News::Newsrc manages newsrc files, of the style

    alt.foo: 1-21,28,31-34
    alt.bar! 3,5,9-2900,2902

Methods are provided for

NEWSRC FILES

A newsrc file is an ASCII file that lists newsgroups and article numbers. Each line of a newsrc file describes a single newsgroup. Each line is divided into three fields: a group, a subscription mark and an article list.

Lines containing only whitespace are ignored. Whitespace within a line is ignored.

Group
The group is the name of the newsgroup. A group name may not contain colons (:) or exclamation points (!).

Group names must be unique within a newsrc file. The group name is required.

Subscription mark
The subscription mark is either a colon (:), for subscribed groups, or an exclamation point (!), for unsubscribed groups. The subscription mark is required.

Article list
The article list is a comma-separated list of positive integers. The integers must be listed in increasing order. Runs of consecutive integers may be abbreviated a-b, where a is the first integer in the run and b is the last. The article list may be empty.

NEWSGROUP ORDER

News::Newsrc preserves the order of newsgroups in a newsrc file: if a file is loaded and then saved, the newsgroup order will be unchanged.

Methods that add or move newsgroups affect the newsgroup order. By default, these methods put newsgroups at the end of the newsrc file. Other locations may be specified by passing an %options hash with a where key to the method. Recognized locations are:

where => 'first'
Put the newsgroup first.

where => 'last'
Put the newsgroup last.

where => 'alpha'
Put the newsgroup in alphabetical order.

If the other newsgroups are not sorted alphabetically, put the group at an arbitrary location.

where => [ before => $group ]
Put the group immediately before $group.

If $group does not exist, put the group last.

where => [ after => $group ]
Put the group immediately after $group.

If $group does not exist, put the group last.

where => [ number => $n ]
Put the group at position $n in the group list. Indices are zero-based. Negative indices count backwards from the end of the list.

METHODS

$newsrc = new News::Newsrc
Creates and returns a News::Newsrc object. The object contains no newsgroups.

$ok = $newsrc->load
$ok = $newsrc->load($file)
Loads the newsgroups in $file into $newsrc. If $file is omitted, reads $ENV{HOME}/.newsrc. Any existing data in $newsrc is discarded. Returns true on success.

If $file can't be opened, load discards existing data from $newsrc and returns null.

If $file contains invalid lines, load will die. When this happens, the state of $newsrc is undefined.

$newsrc->import_rc(@lines)
$newsrc->import_rc([@lines])
Imports the newsgroups in @lines into $newsrc. Any existing data in $newsrc is discarded.

Each line in @lines describes a single newsgroup, and must have the format described in NEWSRC FILES. If @lines contains invalid lines, import_rc will die. When this happens, the state of $newsrc is undefined.

import_rc accepts either an array or an array reference.

$newsrc->save
Writes the contents of $newsrc back to the file from which it was loaded. If load has not been called, writes to $ENV{HOME}/.newsrc. In either case, if the destination file exists, it is renamed to file.bak.

save will die if there is an error writing the file.

$newsrc->save_as($file)
Writes the contents of $newsrc to $file. If $file exists, it is renamed to $file.bak. Subsequent calls to save will write to $file.

save_as will die if there is an error writing the file.

@lines = $newsrc->export_rc
Returns the contents of $newsrc as a list of lines. Each line describes a single newsgroup, and has the format described in NEWSRC FILES.

In scalar context, returns an array reference.

$ok = $newsrc->add_group($group, %options)
Adds $group to the list of newsgroups in $newsrc. $group is initially subscribed. The article list for $group is initially empty.

By default, $group is added to the end of the list of newsgroups. Other locations may be specified in %options; see NEWSGROUP ORDER for details.

By default, add_group does nothing if $group already exists. If the replace => 1 option is provided, then add_group will delete $group if it exists, and then add it.

add_group returns true iff $group was added.

$ok = $newsrc->move_group($group, %options)
Changes the position of $group in $newsrc according to %options. See NEWSGROUP ORDER for details.

If $group does not exist, move_group does nothing and returns false. Otherwise, it returns true.

$ok = $newsrc->del_group($group)
If $group exists in $newsrc, del_group removes it and returns true. The article list for $group is lost.

If $group does not exist in $newsrc, del_group does nothing and returns false.

$newsrc->subscribe($group, %options)
Subscribes to $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->unsubscribe($group, %options)
Unsubscribes from $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->mark($group, $article, %options)
Adds $article to the article list for $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->mark_list($group, \@articles, %options)
Adds @articles to the article list for $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->mark_range($group, $from, $to, %options)
Adds all the articles from $from to $to, inclusive, to the article list for $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->unmark($group, $article, %options)
Removes $article from the article list for $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->unmark_list($group, \@articles, %options)
Removes @articles from the article list for $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->unmark_range($group, $from, $to, %options)
Removes all the articles from $from to $to, inclusive, from the article list for $group.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$newsrc->exists($group)
Returns true iff $group exists in $newsrc.

$newsrc->subscribed($group)
Returns true iff $group exists and is subscribed.

$newsrc->marked($group, $article)
Returns true iff $group exists and its article list contains $article.

$n = $newsrc->num_groups
Returns the number of groups in $newsrc.

@groups = $newsrc->groups
Returns the list of groups in $newsrc, in newsrc order. In scalar context, returns an array reference.

@groups = $newsrc->sub_groups
Returns the list of subscribed groups in $newsrc, in newsrc order. In scalar context, returns an array reference.

@groups = $newsrc->unsub_groups
Returns the list of unsubscribed groups in $newsrc, in newsrc order. In scalar context, returns an array reference.

@articles = $newsrc->marked_articles($group)
Returns the list of articles in the article list for $group. In scalar context, returns an array reference.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

@articles = $newsrc->unmarked_articles($group, $from, $to, %options)
Returns the list of articles from $from to $to, inclusive, that do not appear in the article list for $group. In scalar context, returns an array reference.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

$articles = $newsrc->get_articles($group, %options)
Returns the article list for $group as a string, in the format described in NEWSRC FILES.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

If you plan to do any nontrivial processing on the article list, consider converting it to a Set::IntSpan object:

  $articles = Set::IntSpan->new($newsrc->get_articles('alt.foo'))

$ok = $newsrc->set_articles($group, $articles, %options)
Sets the article list for $group. Any existing article list is lost.

$articles is a string, as described in NEWSRC FILES.

$group will be created if it does not exist. Its location may be specified in %options; see NEWSGROUP ORDER for details.

If $articles does not have the format described in NEWSRC FILES, set_articles does nothing and returns false. Otherwise, it returns true.

DIAGNOSTICS

Bad newsrc line
A line in the newsrc file does not have the format described in NEWSRC FILES.

Bad article list
The article list for a newsgroup does not have the format described in NEWSRC FILES.

News::Newsrc::save_as: Can't rename $file, $file.bak: $!
News::Newsrc::save_as: Can't open $file: $!
News::Newsrc::format: Can't write $file: $!

NOTES

Error Handling

``Don't test for errors that you can't handle.''

load returns null if it can't open the newsrc file, and dies if the newsrc file contains invalid data. This isn't as schizophrenic as it seems.

There are several ways a program could handle an open failure on the newsrc file. It could prompt the user to reenter the file name. It could assume that the user doesn't have a newsrc file yet. If it doesn't want to handle the error, it could go ahead and die.

On the other hand, it is very difficult for a program to do anything sensible if the newsrc file opens successfully and then turns out to contain invalid data. Was there a disk error? Is the file corrupt? Did the user accidentally specify his kill file instead of his newsrc file? And what are you going to do about it?

Rather than try to handle an error like this, it's probably better to die and let the user sort things out. By the same rational, save and save_as die on failure.

Programs that must retain control can use eval{...} to protect calls that may die. For example, Perl/Tk runs all callbacks inside an eval{...}. If a callback dies, Perl/Tk regains control and displays $@ in a dialog box. The user can then decide whether to continue or quit from the program.

import_rc/export_rc

I was going to call these methods import and export, but import turns out not to be a good name for a method, because use also calls import, and expects different semantics.

I added the _rc suffix to import to avoid this conflict. It's reasonably short and somewhat mnemonic (the module manages newsrc files). I added the same suffix to export for symmetry.

AUTHOR

Steven McDougall, swmcd@world.std.com

SEE ALSO

perl(1), Set::IntSpan

COPYRIGHT

Copyright 1996-1998 by Steven McDougall. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

 News::Newsrc - manage newsrc files