docs: Clarify error handler example.

[libguestfs.git] / src / guestfs.pod

diff --git a/src/guestfs.pod b/src/guestfs.pod
index 5d9d804..a1831c0 100644 (file)
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -728,7 +728,7 @@ and we are looking for help to complete this binding.
 =item B<Java>
 
 Full documentation is contained in the Javadoc which is distributed
-with libguestfs.
+with libguestfs.  For examples, see L<guestfs-java(3)>.
 
 =item B<OCaml>
 
@@ -1344,8 +1344,6 @@ been printed to C<stderr> before the program exits.
 For other programs the caller will almost certainly want to install an
 alternate error handler or do error handling in-line like this:
 
- g = guestfs_create ();
- 
  /* This disables the default behaviour of printing errors
     on stderr. */
  guestfs_set_error_handler (g, NULL, NULL);
@@ -1354,9 +1352,12 @@ alternate error handler or do error handling in-line like this:
    /* Examine the error message and print it etc. */
    char *msg = guestfs_last_error (g);
    int errnum = guestfs_last_errno (g);
-   fprintf (stderr, "%s\n", msg);
+   fprintf (stderr, "%s", msg);
+   if (errnum != 0)
+     fprintf (stderr, ": %s", strerror (errnum));
+   fprintf (stderr, "\n");
    /* ... */
-  }
+ }
 
 Out of memory errors are handled differently.  The default action is
 to call L<abort(3)>.  If this is undesirable, then you can set a
@@ -1949,6 +1950,45 @@ this example, messages are directed to syslog:
      syslog (priority, "event 0x%lx: %s", event, buf);
  }
 
+=head1 CANCELLING LONG TRANSFERS
+
+Some operations can be cancelled by the caller while they are in
+progress.  Currently only operations that involve uploading or
+downloading data can be cancelled (technically: operations that have
+C<FileIn> or C<FileOut> parameters in the generator).
+
+=head2 guestfs_user_cancel
+
+ void guestfs_user_cancel (guestfs_h *g);
+
+C<guestfs_user_cancel> cancels the current upload or download
+operation.
+
+Unlike most other libguestfs calls, this function is signal safe and
+thread safe.  You can call it from a signal handler or from another
+thread, without needing to do any locking.
+
+The transfer that was in progress (if there is one) will stop shortly
+afterwards, and will return an error.  The errno (see
+L</guestfs_last_errno>) is set to C<EINTR>, so you can test for this
+to find out if the operation was cancelled or failed because of
+another error.
+
+No cleanup is performed: for example, if a file was being uploaded
+then after cancellation there may be a partially uploaded file.  It is
+the caller's responsibility to clean up if necessary.
+
+There are two common places that you might call C<guestfs_user_cancel>.
+
+In an interactive text-based program, you might call it from a
+C<SIGINT> signal handler so that pressing C<^C> cancels the current
+operation.  (You also need to call L</guestfs_set_pgroup> so that
+child processes don't receive the C<^C> signal).
+
+In a graphical program, when the main thread is displaying a progress
+bar with a cancel button, wire up the cancel button to call this
+function.
+
 =head1 PRIVATE DATA AREA
 
 You can attach named pieces of private data to the libguestfs handle,
@@ -2658,6 +2698,11 @@ Automated tests of the C API.
 The L<virt-cat(1)>, L<virt-filesystems(1)> and L<virt-ls(1)> commands
 and documentation.
 
+=item C<caution>
+
+Safety and liveness tests of components that libguestfs depends upon
+(not of libguestfs itself).  Mainly this is for qemu and the kernel.
+
 =item C<contrib>
 
 Outside contributions, experimental parts.
@@ -2671,6 +2716,10 @@ actions.
 
 L<virt-df(1)> command and documentation.
 
+=item C<edit>
+
+L<virt-edit(1)> command and documentation.
+
 =item C<examples>
 
 C API example code.
@@ -2759,6 +2808,61 @@ Language bindings.
 
 =back
 
+=head2 MAKING A STABLE RELEASE
+
+When we make a stable release, there are several steps documented
+here.  See L</LIBGUESTFS VERSION NUMBERS> for general information
+about the stable branch policy.
+
+=over 4
+
+=item *
+
+Check C<make && make check> works on at least Fedora, Debian and
+Ubuntu.
+
+=item *
+
+Finalize RELEASE-NOTES.
+
+=item *
+
+Update ROADMAP.
+
+=item *
+
+Run C<src/api-support/update-from-tarballs.sh>.
+
+=item *
+
+Push and pull from Transifex.
+
+Run:
+
+ tx push -s
+
+to push the latest POT files to Transifex.  Then run:
+
+ ./tx-pull.sh
+
+which is a wrapper to pull the latest translated C<*.po> files.
+
+=item *
+
+Create new stable and development directories under
+L<http://libguestfs.org/download>.
+
+=item *
+
+Create the branch in git:
+
+ git tag -a 1.XX.0 -m "Version 1.XX.0 (stable)"
+ git tag -a 1.YY.0 -m "Version 1.YY.0 (development)"
+ git branch stable-1.XX
+ git push origin tag 1.XX.0 1.YY.0 stable-1.XX
+
+=back
+
 =head1 LIMITS
 
 =head2 PROTOCOL LIMITS
@@ -2863,6 +2967,16 @@ be reached in practice.  See the source code for more information.
 
 =over 4
 
+=item FEBOOTSTRAP_KERNEL
+
+=item FEBOOTSTRAP_MODULES
+
+These two environment variables allow the kernel that libguestfs uses
+in the appliance to be selected.  If C<$FEBOOTSTRAP_KERNEL> is not
+set, then the most recent host kernel is chosen.  For more information
+about kernel selection, see L<febootstrap-supermin-helper(8)>.  This
+feature is only available in febootstrap E<ge> 3.8.
+
 =item LIBGUESTFS_APPEND
 
 Pass additional options to the guest kernel.
@@ -2913,7 +3027,9 @@ enough.
 =head1 SEE ALSO
 
 L<guestfs-examples(3)>,
+L<guestfs-java(3)>,
 L<guestfs-ocaml(3)>,
+L<guestfs-perl(3)>,
 L<guestfs-python(3)>,
 L<guestfs-ruby(3)>,
 L<guestfish(1)>,
@@ -2936,6 +3052,7 @@ L<virt-tar-out(1)>,
 L<virt-win-reg(1)>,
 L<qemu(1)>,
 L<febootstrap(1)>,
+L<febootstrap-supermin-helper(8)>,
 L<hivex(3)>,
 L<http://libguestfs.org/>.