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--- packages:alternatives [2016-02-01 06:14] – created glen
+++ packages:alternatives [2016-02-01 06:25] (current) – glen
@@ Line 1: / Line 1: @@
 ====== alternatives ======
-[[http://linux.die.net/man/8/update-alternatives|update-alternatives]] - maintain symbolic links determining default commands
+[[http://linux.die.net/man/8/update-alternatives|update-alternatives]] - maintain symbolic links determining default commands.
+Default implementation in PLD Linux is provided by ''alternatives'' package from [[package>chkconfig]].
+===== switching alternative =====
+By default ''alternatives'' uses ''auto'' mode picking the "best" alternative.
+//TODO: how to enforce sysadmin preference//
+===== integrating =====
+from [[http://git.pld-linux.org/?p=packages/php.git;a=commitdiff;h=82885e7c57e9ee9183eead2319352703c8278a35|phar-php example]]:
+<code rpmspec>
+Requires:      alternatives
+...
+%install
+...
+# touch for ghost
+%{__rm} $RPM_BUILD_ROOT%{_bindir}/phar
+touch $RPM_BUILD_ROOT%{_bindir}/phar
+%post phar
+update-alternatives \
+       --install %{_bindir}/phar phar %{_bindir}/phar%{ver_suffix}.phar %{ver_suffix} \
+       --slave %{_mandir}/man1/phar.1 phar.1 %{_mandir}/man1/phar%{ver_suffix}.1* || :
+%postun phar
+if [ $1 -eq 0 ]; then
+       update-alternatives --remove phar %{_bindir}/phar || :
+fi
+...
+%files
+...
+%ghost %{_bindir}/phar
+%ghost %{_mandir}/man1/phar.1
+</code>
+  - add ''Requires: alternatives'' to runtime deps
+  - the path must be ghost and regular file, otherwise rpm will complin about file-conflicts
+  - use ''%%--install%%'' to setup the symlinks in package ''%post'' scriptlet.
+  - the ''%%--slave%%'' option is optional and may be repeated, use if you wish to "group" alternatives
+  - use proper ''%postun'' to remove alternative on package uninstall
+<note warning>
+Currently it remains unclear how to handle optional files, as for above example:
+  - ''%{_mandir}'' path can be missing if ''%_excludedocs'' is set
+  - ''%{_mandir}'' path could be ''.gz'' compressed or not, it's currently solved with a glob: ''%{_mandir}/man1/phar%{ver_suffix}.1*''
+</note>