| 1 | #!/usr/bin/perl |
| 2 | |
| 3 | use strict; |
| 4 | use Cwd 'abs_path'; |
| 5 | |
| 6 | my $RSYNC = '/usr/bin/rsync'; |
| 7 | |
| 8 | my $dest_dir = $ARGV[-1]; |
| 9 | usage(1) if $dest_dir eq '' || $dest_dir =~ /^--/; |
| 10 | |
| 11 | if (!-d $dest_dir) { |
| 12 | print STDERR "$dest_dir is not a directory.\n\n"; |
| 13 | usage(1); |
| 14 | } |
| 15 | |
| 16 | if (@_ = grep(/^--(link|compare)-dest/, @ARGV)) { |
| 17 | $_ = join(' or ', @_); |
| 18 | print STDERR "You may not use $_ as an rsync option.\n\n"; |
| 19 | usage(1); |
| 20 | } |
| 21 | |
| 22 | $dest_dir = abs_path($dest_dir); |
| 23 | if ($dest_dir eq '/') { |
| 24 | print STDERR 'You must not use "/" as the destination directory.', "\n\n"; |
| 25 | usage(1); |
| 26 | } |
| 27 | |
| 28 | my $old_dir = "$dest_dir~old~"; |
| 29 | my $new_dir = $ARGV[-1] = "$dest_dir~new~"; |
| 30 | |
| 31 | if (-d $old_dir) { |
| 32 | rename($old_dir, $new_dir) or die "Unable to rename $old_dir to $new_dir: $!"; |
| 33 | } |
| 34 | |
| 35 | if (system($RSYNC, "--link-dest=$dest_dir", @ARGV)) { |
| 36 | if ($? == -1) { |
| 37 | print "failed to execute $RSYNC: $!\n"; |
| 38 | } elsif ($? & 127) { |
| 39 | printf "child died with signal %d, %s coredump\n", |
| 40 | ($? & 127), ($? & 128) ? 'with' : 'without'; |
| 41 | } else { |
| 42 | printf "child exited with value %d\n", $? >> 8; |
| 43 | } |
| 44 | exit $?; |
| 45 | } |
| 46 | |
| 47 | rename($dest_dir, $old_dir) or die "Unable to rename $new_dir to $old_dir: $!"; |
| 48 | rename($new_dir, $dest_dir) or die "Unable to rename $new_dir to $dest_dir: $!"; |
| 49 | |
| 50 | exit; |
| 51 | |
| 52 | |
| 53 | sub usage |
| 54 | { |
| 55 | my($ret) = @_; |
| 56 | my $fh = $ret ? *STDERR : *STDOUT; |
| 57 | print $fh <<EOT; |
| 58 | Usage: atomic-rsync [RSYNC-OPTIONS] HOST:SOURCE DEST |
| 59 | |
| 60 | This script allows you to pull some files into DEST on the local system |
| 61 | (which must exist) in an atomic manner. It does this by first pulling |
| 62 | files to DEST~new~ (using hard-links to unchanged files in order to keep |
| 63 | the space requirements down), and then, at the end of the transfer, it |
| 64 | renames DEST to DEST~old~ and renames DEST~new~ to DEST to effect the |
| 65 | atomic update. The DEST~old~ hierarchy will be preserved until the next |
| 66 | run of this script, at which point it will be renamed to DEST~new~ and |
| 67 | used in the copy. |
| 68 | |
| 69 | See the "rsync" command for its list of options. You may not use the |
| 70 | --link-dest or --compare-dest options (since this script uses --link-dest |
| 71 | to effect the atomic transfer). Also, DEST cannot be "/". |
| 72 | EOT |
| 73 | exit $ret; |
| 74 | } |