Add a --query option to update-alternatives. Closes: #336091, #441904

* scripts/update-alternatives.pl: add a --query option that works like
--display but outputs a machine parseable rfc822-like output.
* man/update-alternatives.8: document that new option, and the
associated format.

ChangeLog

@@ -1,3 +1,10 @@
+2008-05-11  Pierre Habouzit  <madcoder@debian.org>
+
+	* scripts/update-alternatives.pl: add a --query option that works like
+	--display but outputs a machine parseable rfc822-like output.
+	* man/update-alternatives.8: document that new option, and the
+	associated format.
+
 2008-05-05  Raphael Hertzog  <hertzog@debian.org>
 
 	* scripts/dpkg-gensymbols.pl: Do not accept empty parameters for

THANKS

@@ -132,6 +132,7 @@ Peter Mann <Peter.Mann@tuke.sk>
 Peter van Dijk <peter@dataloss.nl>
 Petr Cech <cech@atrey.karlin.mff.cuni.cz>
 Philippe Batailler <pbatailler@teaser.fr>
+Pierre Habouzit <madcoder@debian.org>
 Piotr Engelking <inkerman42@gmail.com>
 Piotr Roszatycki <dexter@fnet.pl>
 Rakesh 'arky' Ambati <rakesh_ambati@yahoo.com>

TODO

@@ -106,8 +106,6 @@ lenny
 
  * Make dpkg-deb --build check for duped conffiles. (#131633)
 
- * Make update-alternatives --display support --quiet. (#336091)
-
  * Propagate --admindir to programs run from maintainer scritpts. (#97076)
 
  * Fix quotes? <http://www.cl.cam.ac.uk/~mgk25/ucs/quotes.html>

debian/changelog

@@ -10,6 +10,9 @@ dpkg (1.15.0) UNRELEASED; urgency=low
   * dpkg-gensymbols now refuses empty values for the the -v -P and -e
     parameters.
 
+  [ Pierre Habouzit ]
+  * Add a --query option to update-alternatives. Closes: #336091, #441904
+
   [ Updated dpkg translations ]
   * Portuguese (Miguel Figueiredo).
 

man/update-alternatives.8

@@ -283,6 +283,12 @@ what other alternatives are available
 (and their corresponding slave alternatives),
 and the highest priority alternative currently installed.
 .TP
+\fB\-\-query\fR \fIlink\fR
+Display information about the link group of which
+.I link
+is the master link like \-\-display does, but in a machine parseable way
+(see section \fBQUERY FORMAT\fR below).
+.TP
 \fB\-\-list\fR \fIlink\fR
 Display all targets of the link group.
 .TP
@@ -339,6 +345,76 @@ The requested action was successfully performed.
 Problems were encountered whilst parsing the command line
 or performing the action.
 .
+.SH "QUERY FORMAT"
+The \fBupdate\-alternatives\fP \fI\-\-query\fP format is using an
+RFC822-like flat format. It's made of \fIn\fP + 1 blocks where \fIn\fP is
+the number of alternatives available in the queried link group. The first
+block contains the following fields:
+.TP
+.BR Link: " <link>"
+The generic name of the alternative.
+.TP
+.BR Status: " <status>"
+The status of the alternative (\fBauto\fR or \fBmanual\fR).
+.TP
+.BR Best: " <best choice>"
+The path of the best alternative for this link group. Not present if
+there is no alternatives available.
+.TP
+.BR Value: " <currently selected alternative> "
+The path of the currently selected alternative. It can also take the magic
+values \fBnone\fR or \fBerror\fR. The former is used if the link doesn't
+exist, and the latter in case of error.
+.TP
+.BR Error: " <error details>"
+When \fBValue\fR is \fBerror\fR, this field is present and contains a human readable
+string explaining the error.
+.
+.TP
+The other blocks describe the available alternatives in the queried link group:
+.TP
+.BR Alternative: " <path of this alternative>"
+Path to this block's alternative.
+.TP
+.BR Priority: " <priority value>"
+Value of the priority of this alternative.
+.TP
+.BR Slaves: " <list of slaves>"
+When this header is present, the \fBnext\fR lines hold all slave alternatives
+associated to the master link of the alternative. There is one slave per
+line. Each line contains one space, the generic name of the slave
+alternative, another space, and the path to the slave alternative.
+.
+.TP
+.BR Example
+.nf
+$ update\-alternatives \-\-query editor
+Link: editor
+Status: auto
+Best: /usr/bin/vim.gtk
+Value: /usr/bin/vim.gtk
+
+Alternative: /bin/ed
+Priority: \-100
+Slaves:
+ editor.1.gz /usr/share/man/man1/ed.1.gz
+
+Alternative: /usr/bin/vim.gtk
+Priority: 50
+Slaves:
+ editor.1.gz /usr/share/man/man1/vim.1.gz
+ editor.ru.1.gz /usr/share/man/ru/man1/vim.1.gz
+ editor.pl.ISO8859-2.1.gz /usr/share/man/pl.ISO8859-2/man1/vim.1.gz
+ editor.it.ISO8859-1.1.gz /usr/share/man/it.ISO8859-1/man1/vim.1.gz
+ editor.pl.UTF-8.1.gz /usr/share/man/pl.UTF-8/man1/vim.1.gz
+ editor.it.1.gz /usr/share/man/it/man1/vim.1.gz
+ editor.fr.UTF-8.1.gz /usr/share/man/fr.UTF-8/man1/vim.1.gz
+ editor.fr.1.gz /usr/share/man/fr/man1/vim.1.gz
+ editor.it.UTF-8.1.gz /usr/share/man/it.UTF-8/man1/vim.1.gz
+ editor.pl.1.gz /usr/share/man/pl/man1/vim.1.gz
+ editor.fr.ISO8859-1.1.gz /usr/share/man/fr.ISO8859-1/man1/vim.1.gz
+.fi
+.
 .SH DIAGNOSTICS
 .B update\-alternatives
 chatters incessantly about its activities on its standard output channel.

scripts/update-alternatives.pl

@@ -17,7 +17,7 @@ $admindir = $admindir . '/alternatives';
 
 my $verbosemode = 0;
 
-my $action = '';      # Action to perform (display / install / remove / display / auto / config)
+my $action = '';      # Action to perform (display / query / install / remove / auto / config)
 my $mode = 'auto';    # Update mode for alternative (manual / auto)
 my $state;            # State of alternative:
                       #   expected: alternative with highest priority is the active alternative
@@ -78,6 +78,7 @@ Commands:
   --remove-all <name>      remove <name> group from the alternatives system.
   --auto <name>            switch the master link <name> to automatic mode.
   --display <name>         display information about the <name> group.
+  --query <name>           machine parseable version of --display <name>.
   --list <name>            display all targets of the <name> group.
   --config <name>          show alternatives for the <name> group and ask the
                            user to select which one to use.
@@ -212,6 +213,38 @@ sub display_link_group
     }
 }
 
+sub query_link_group
+{
+    pr(sprintf("Link: %s", $name));
+    pr(sprintf("Status: %s", $mode));
+    if ($best ne '') {
+	pr(sprintf("Best: %s", $best));
+    }
+    $linkname = readlink("$altdir/$name");
+
+    if (defined($linkname)) {
+	pr(sprintf("Value: %s", $linkname));
+    } elsif ($! == ENOENT) {
+	pr("Value: none");
+    } else {
+	pr("Value: error");
+	pr(sprintf("Error: %s", $!));
+    }
+
+    for (my $i = 0; $i <= $#versions; $i++) {
+	pr("");
+	pr(sprintf("Alternative: %s", $versions[$i]));
+	pr(sprintf("Priority: %s", $priorities[$i]));
+	next unless ($#slavenames >= 0);
+	pr("Slaves:");
+	for (my $j = 0; $j <= $#slavenames; $j++) {
+	    my $tspath = $slavepath{$i, $j};
+	    next unless length($tspath);
+	    pr(sprintf(" %s %s", $slavenames[$j], $tspath));
+	}
+    }
+}
+
 sub list_link_group
 {
     for (my $i = 0; $i <= $#versions; $i++) {
@@ -314,7 +347,7 @@ while (@ARGV) {
         @ARGV >= 2 || &badusage(sprintf(_g("--%s needs <name> <path>"), $1));
         ($name,$apath,@ARGV) = @ARGV;
 	$action = $1;
-    } elsif (m/^--(display|auto|config|list|remove-all)$/) {
+    } elsif (m/^--(display|query|auto|config|list|remove-all)$/) {
 	check_many_actions();
         @ARGV || &badusage(sprintf(_g("--%s needs <name>"), $1));
 	$action = $1;
@@ -345,7 +378,7 @@ defined($alink) && $aslavelinkcount{$alink} &&
   badusage(sprintf(_g("link %s is both primary and slave"), $alink));
 
 $action ||
-  badusage(_g("need --display, --config, --set, --install, --remove, --all, --remove-all or --auto"));
+  badusage(_g("need --display, --query, --config, --set, --install, --remove, --all, --remove-all or --auto"));
 $action eq 'install' || !%aslavelink ||
   badusage(_g("--slave only allowed with --install"));
 
@@ -371,6 +404,12 @@ if ($action eq 'display') {
     exit 0;
 }
 
+if ($action eq 'query') {
+    find_best_version();
+    query_link_group();
+    exit 0;
+}
+
 if ($action eq 'list') {
     list_link_group();
     exit 0;