NAME¶
News::Newsrc - manage newsrc files
SYNOPSIS¶
use News::Newsrc;
$newsrc = new News::Newsrc;
$newsrc = new News::Newsrc $file;
$newsrc = new News::Newsrc $file, create => 1;
$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 5.6.0, 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
- •
- reading and writing newsrc files
- •
- adding and removing newsgroups
- •
- changing the order of 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.
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"
- $newsrc = "new"
"News::Newsrc" $file,
%options
- Creates and returns a "News::Newsrc" object.
If $file is specified, "new" loads the
newsgroups in $file into the object. Subsequent calls
to "save" will write to $file.
If $file exists and the load fails, "new"
"die"s.
If $file doesn't exist and the "create =>
1" option is supplied in %options, then
"new" doesn't load any newsgroups.
If $file doesn't exist and the "create =>
1" option is not supplied in %options, then
"new" dies.
- $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 "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" 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 news
rc
files). I added the same suffix to "export" for symmetry.
ACKNOWLEDGMENTS¶
- •
- Neil Bowers <neilb@cre.canon.co.uk>
- •
- Matthew Darwin <matthew@davin.ottawa.on.ca>
- •
- Philip Hallstrom
<philip.hallstrom@cendantsoft.com>
- •
- M. Hedlund <hedlund@best.com>
- •
- Bruce J. Keeler <bruce@gridpoint.com>
- •
- Chris Leach <Chris.Leach@epa.ericsson.se>
- •
- Abhijit Menon-Sen <ams@wiw.org>
- •
- J.B. Nicholson-Owens
<jbn@pop-a-wheelie.midwest.net>
- •
- Lars Balker Rasmussen <gnort@daimi.aau.dk>
- •
- Mike Stok <mike@stok.co.uk>
- •
- Bennett Todd <bet@onyx.interactive.net>
- •
- Larry W. Virden <lvirden@cas.org>
- •
- Chris Szurgot <szurgot@itribe.net>
AUTHOR¶
Steven McDougall, swmcd@world.std.com
SEE ALSO¶
perl(1), Set::IntSpan
COPYRIGHT¶
Copyright 1996-2007 by Steven McDougall. This module is free software; you can
redistribute it and/or modify it under the same terms as Perl itself.