/ 
News-Newsrc-1.02
River stage zero No dependents
/ News::Newsrc

NAME

News::Newsrc - manage newsrc files

SYNOPSIS

    use News::Newsrc;

    $newsrc = new News::Newsrc;
    
    $newsrc->load();
    $newsrc->load($file);
    
    $newsrc->save();
    $newsrc->save_as($file);

    $newsrc->add_group($group);
    $newsrc->del_group($group);
	
    $newsrc->subscribe  ($group);
    $newsrc->unsubscribe($group);

    $newsrc->mark        ($group,  $article);
    $newsrc->mark_list   ($group, \@articles);
    $newsrc->mark_range  ($group, $from, $to);
    
    $newsrc->unmark      ($group,  $article);
    $newsrc->unmark_list ($group, \@articles);
    $newsrc->unmark_range($group, $from, $to);
    
    ... if $newsrc->exists    ($group);
    ... if $newsrc->subscribed($group);
    ... if $newsrc->marked    ($group, $article);
    
    @groups   = $newsrc->groups();
    @groups   = $newsrc->sub_groups();
    @groups   = $newsrc->unsub_groups();
    @articles = $newsrc->marked_articles($group);
    @articles = $newsrc->unmarked_articles($group, $from, $to);

REQUIRES

Perl 5.002, Exporter, Set::IntSpan 1.01

EXPORTS

None

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

  • reading and writing newsrc files

  • adding and removing newsgroups

  • subscribing and unsubscribing from newsgroups

  • testing whether groups exist and are subscribed

  • marking and unmarking articles

  • testing whether articles are marked

  • returning lists of newsgroups

  • returning lists of articles

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.

METHODS

new News::Newsrc

Creates and returns a News::Newsrc object. The object contains no newsgroups.

load()
load($file)

Loads the newsgroups in $file into a newsrc object. If $file is omitted, reads $ENV{HOME}/.newsrc. Any existing data in the object is discarded. Returns non-null on success.

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

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

save()

Writes the contents of a newsrc object back to the file from which it was load()ed. 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_as($file)

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

add_group($group)

Adds $group to the list of newsgroups in a newsrc object. $group is initially subscribed. The article list for $group is initially empty.

del_group($group)

Removes $group from the list of groups in a newsrc object. The article list for $group is lost.

subscribe($group)

Subscribes to $group. $group will be created if it does not exist.

unsubscribe($group)

Unsubscribes from $group. $group will be created if it does not exist.

mark($group, $article)

Adds $article to the article list for $group. $group will be created if it does not exist.

mark_list($group, \@articles)

Adds @articles to the article list for $group. $group will be created if it does not exist.

mark_range($group, $from, $to)

Adds all the articles from $from to $to, inclusive, to the article list for $group. $group will be created if it does not exist.

unmark($group, $article)

Removes $article from the article list for $group. $group will be created if it does not exist.

unmark_list($group, \@articles)

Removes @articles from the article list for $group. $group will be created if it does not exist.

unmark_range($group, $from, $to)

Removes all the articles from $from to $to, inclusive, from the article list for $group. $group will be created if it does not exist.

exists($group)

Returns true if $group exists in the newsrc object.

subscribed($group)

Returns true if $group exists and is subscribed.

marked($group, $article)

Returns true if $group exists and its article list contains $article.

groups()

Returns the list of groups in a newsrc object. In scalar context, returns an array reference.

sub_groups()

Returns the list of subscribed groups in a newsrc object. In scalar context, returns an array reference.

unsub_groups()

Returns the list of unsubscribed groups in a newsrc object. In scalar context, returns an array reference.

marked_articles($group)

Returns the list of articles in the article list for $group. In scalar context, returns an array reference.

unmarked_articles($group, $from, $to)

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.

DIAGNOSTICS

load() returns null if it can't open the newsrc file.

load() will die() if the newsrc file contains invalid lines.

save() and save_as() will die() if they can't backup or write the newsrc file.

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.

AUTHOR

Steven McDougall, swm@cric.com

SEE ALSO

perl(1), Set::IntSpan

COPYRIGHT

Copyright (c) 1996 Steven McDougall. All rights reserved. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.