Upgrade tar-snapshot-edit script.

* scripts/tar-snapshot-edit: Update Perl syntax to work
correctly with more recent versions of Perl.  (The original
code worked with in the v5.8 timeframe but not with
Perl v5.10.1 and later.)
Add a "-c" option to check the snapshot file for invalid
field values.
Handle NFS indicator character ("+") in version 0 and 1 files.
Preserve the original header/version line when editing version 1
or 2 files.
Tweak output formatting.
* doc/tar-snapshot-edit.texi: Update documentation.

doc/tar-snapshot-edit.texi

@@ -6,24 +6,28 @@
 @cindex Device numbers, changing
 @cindex snapshot files, editing
 @cindex snapshot files, fixing device numbers
-  Sometimes device numbers can change after upgrading your kernel
-version or reconfiguring the hardware.  Reportedly this is the case with
-some newer @i{Linux} kernels, when using @acronym{LVM}.  In majority of
+  Various situations can cause device numbers to change: upgrading your
+kernel version, reconfiguring your hardware, loading kernel modules in a
+different order, using virtual volumes that are assembled dynamically
+(such as with @acronym{LVM} or @acronym{RAID}), hot-plugging drives
+(e.g. external USB or Firewire drives), etc.  In the majority of 
 cases this change is unnoticed by the users.  However, it influences
 @command{tar} incremental backups: the device number is stored in tar
 snapshot files (@pxref{Snapshot Files}) and is used to determine whether
 the file has changed since the last backup.  If the device numbers
-change for some reason, the next backup you run will be a full backup.
+change for some reason, by default the next backup you run will be a
+full backup.
+
 
 @pindex tar-snapshot-edit
   To minimize the impact in these cases, GNU @command{tar} comes with
 the @command{tar-snapshot-edit} utility for inspecting and updating
-device numbers in snapshot files.  The utility, written by
-Dustin J.@: Mitchell, is available from
+device numbers in snapshot files.  (The utility, written by
+Dustin J.@: Mitchell, is also available from the
 @uref{http://www.gnu.org/@/software/@/tar/@/utils/@/tar-snapshot-edit.html,
-@GNUTAR{} home page}.
+@GNUTAR{} home page}.)
 
-  To obtain the device numbers used in the snapshot file, run
+  To obtain a summary of the device numbers found in the snapshot file, run
 
 @smallexample
 $ @kbd{tar-snapshot-edit @var{snapfile}}
@@ -31,10 +35,19 @@ $ @kbd{tar-snapshot-edit @var{snapfile}}
 
 @noindent
 where @var{snapfile} is the name of the snapshot file (you can supply as many
-files as you wish in a single command line).
+files as you wish in a single command line).  You can then compare the 
+numbers across snapshot files, or against those currently in use on the
+live filesystem (using @command{ls -l} or @command{stat}).
+
+  Assuming the device numbers have indeed changed, it's often possible
+to simply tell @GNUTAR{} to ignore the device number when processing the
+incremental snapshot files for these backups, using the
+@option{--no-check-device} option (@pxref{device numbers}).
 
-To update all occurrences of the given device number in the file, use
-@option{-r} option.  It takes a single argument of the form
+  Alternatively, you can use the @command{tar-edit-snapshot} script's 
+@option{-r} option to update all occurrences of the given device
+number in the snapshot file(s).  It takes a single argument
+of the form
 @samp{@var{olddev}-@var{newdev}},  where @var{olddev} is the device number
 used in the snapshot file, and @var{newdev} is the corresponding new device
 number.  Both numbers may be specified in hex (e.g., @samp{0xfe01}),
@@ -49,9 +62,30 @@ backup file is obtained by appending @samp{~} to the original file name.
 
 An example session:
 @smallexample
-$ @kbd{tar-snapshot-edit /var/backup/snap.a}
-file version 2
-/tmp/snap: Device 0x0306 occurs 634 times.
-$ @kbd{tar-snapshot-edit -b -r 0x0306-0x4500 /var/backup/snap.a}
-file version 2
+$ @kbd{tar-snapshot-edit root_snap.0 boot_snap.0}
+File: root_snap.0
+  Detected snapshot file version: 2
+
+  Device 0x0000 occurs 1 times.
+  Device 0x0003 occurs 1 times.
+  Device 0x0005 occurs 1 times.
+  Device 0x0013 occurs 1 times.
+  Device 0x6801 occurs 1 times.
+  Device 0x6803 occurs 6626 times.
+  Device 0xfb00 occurs 1 times.
+
+File: boot_snap.0
+  Detected snapshot file version: 2
+
+  Device 0x6801 occurs 3 times.
+$ @kbd{tar-snapshot-edit -b -r 0x6801-0x6901,0x6803-0x6903 root_snap.0 boot_snap.0}
+File: root_snap.0
+  Detected snapshot file version: 2
+
+  Updated 6627 records.
+
+File: boot_snap.0
+  Detected snapshot file version: 2
+
+  Updated 3 records.
 @end smallexample

scripts/tar-snapshot-edit

@@ -1,10 +1,10 @@
 #! /usr/bin/perl -w
 # Display and edit the 'dev' field in tar's snapshots
-# Copyright (C) 2007 Free Software Foundation, Inc.
+# Copyright (C) 2007,2011 Free Software Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 3, or (at your option)
+# the Free Software Foundation; either version 2, or (at your option)
 # any later version.
 #
 # This program is distributed in the hope that it will be useful,
@@ -17,13 +17,37 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 # 02110-1301, USA.
 #
-# Author: Dustin J. Mitchell <[email protected]>
+#
+# tar-snapshot-edit
 #
 # This script is capable of replacing values in the 'dev' field of an
 # incremental backup 'snapshot' file.  This is useful when the device
 # used to store files in a tar archive changes, without the files
 # themselves changing.  This may happen when, for example, a device
 # driver changes major or minor numbers.
+#
+# It can also run a check on all the field values found in the
+# snapshot file, printing out a detailed message when it finds values
+# that would cause an "Unexpected field value in snapshot file" error
+# if tar were run using that snapshot file as input.  (See the
+# comments included in the definition of the check_field_values
+# routine for more detailed information regarding these checks.)
+#
+#
+#
+# Author: Dustin J. Mitchell <[email protected]>
+#
+# Modified Aug 25, 2011 by Nathan Stratton Treadway <nathanst AT ontko.com>:
+#   * update Perl syntax to work correctly with more recent versions of
+#     Perl.  (The original code worked with in the v5.8 timeframe but 
+#     not with Perl v5.10.1 and later.)
+#   * added a "-c" option to check the snapshot file for invalid field values.
+#   * handle NFS indicator character ("+") in version 0 and 1 files
+#   * preserve the original header/version line when editing version 1
+#     or 2 files.
+#   * tweak output formatting
+#
+#
 
 use Getopt::Std;
 
@@ -41,14 +65,15 @@ sub read_incr_db ($) {
 	$file_version = 0;
     }
 
-    print "file version $file_version\n";
+    print "\nFile: $filename\n";
+    print "  Detected snapshot file version: $file_version\n\n";
 
     if ($file_version == 0) {
 	return read_incr_db_0($file, $header_str);
     } elsif ($file_version == 1) {
-	return read_incr_db_1($file);
+	return read_incr_db_1($file, $header_str);
     } elsif ($file_version == 2) {
-	return read_incr_db_2($file);
+	return read_incr_db_2($file, $header_str);
     } else {
 	die "Unrecognized snapshot version in header '$header_str'";
     }
@@ -62,48 +87,66 @@ sub read_incr_db_0 ($$) {
     chop $hdr_timestamp_sec;
     my $hdr_timestamp_nsec = ''; # not present in file format 0
 
+    my $nfs;
     my @dirs;
 
     while (<$file>) {
-	/^([0-9]*) ([0-9]*) (.*)\n$/ || die("Bad snapshot line $_");
+	/^(\+?)([0-9]*) ([0-9]*) (.*)\n$/ || die("Bad snapshot line $_");
 
-	push @dirs, { dev=>$1,
-		      ino=>$2,
-		      name=>$3 };
+        if ( $1 eq "+" ) {
+          $nfs="1";
+        } else {
+          $nfs="0";
+        }
+	push @dirs, { nfs=>$nfs,
+		      dev=>$2,
+		      ino=>$3,
+		      name=>$4 };
     }
 
     close($file);
 
-    # file version, timestamp, timestamp, dir list
-    return [ 0, $hdr_timestamp_sec, $hdr_timestamp_nsec, \@dirs ];
+    # file version, timestamp, timestamp, dir list, file header line
+    return [ 0, $hdr_timestamp_sec, $hdr_timestamp_nsec, \@dirs, ""];
 }
 
-sub read_incr_db_1 ($) {
+sub read_incr_db_1 ($$) {
     my $file = shift;
+    my $header_str = shift;
+
 
     my $timestamp = <$file>; # "sec nsec"
     my ($hdr_timestamp_sec, $hdr_timestamp_nsec) = ($timestamp =~ /([0-9]*) ([0-9]*)/);
 
+    my $nfs;
     my @dirs;
 
     while (<$file>) {
-	/^([0-9]*) ([0-9]*) ([0-9]*) ([0-9]*) (.*)\n$/ || die("Bad snapshot line $_");
-
-	push @dirs, { timestamp_sec=>$1,
-		      timestamp_nsec=>$2,
-		      dev=>$3,
-		      ino=>$4,
-		      name=>$5 };
+	/^(\+?)([0-9]*) ([0-9]*) ([0-9]*) ([0-9]*) (.*)\n$/ || die("Bad snapshot line $_");
+
+        if ( $1 eq "+" ) {
+          $nfs="1";
+        } else {
+          $nfs="0";
+        }
+ 
+	push @dirs, { nfs=>$nfs,
+		      timestamp_sec=>$2,
+		      timestamp_nsec=>$3,
+		      dev=>$4,
+		      ino=>$5,
+		      name=>$6 };
     }
 
     close($file);
 
-    # file version, timestamp, timestamp, dir list
-    return [ 1, $hdr_timestamp_sec, $hdr_timestamp_nsec, \@dirs ];
+    # file version, timestamp, timestamp, dir list, file header line
+    return [ 1, $hdr_timestamp_sec, $hdr_timestamp_nsec, \@dirs, $header_str ];
 }
 
-sub read_incr_db_2 ($) {
+sub read_incr_db_2 ($$) {
     my $file = shift;
+    my $header_str = shift;
 
     $/="\0"; # $INPUT_RECORD_SEPARATOR
     my $hdr_timestamp_sec = <$file>;
@@ -150,40 +193,158 @@ sub read_incr_db_2 ($) {
     close($file);
     $/ = "\n"; # reset to normal
 
-    # file version, timestamp, timestamp, dir list
-    return [ 2, $hdr_timestamp_sec, $hdr_timestamp_nsec, \@dirs ];
+    # file version, timestamp, timestamp, dir list, file header line
+    return [ 2, $hdr_timestamp_sec, $hdr_timestamp_nsec, \@dirs,  $header_str];
 }
 
 ## display
 
-sub show_device_counts ($$) {
+sub show_device_counts ($) {
     my $info = shift;
-    my $filename = shift;
     my %devices;
-    foreach my $dir (@{${@$info}[3]}) {
-	my $dev = ${%$dir}{'dev'};
+    foreach my $dir (@{$info->[3]}) {
+	my $dev = $dir->{'dev'};
 	$devices{$dev}++;
     }
 
-    foreach $dev (sort keys %devices) {
-	printf "$filename: Device 0x%04x occurs $devices{$dev} times.\n", $dev;
+    foreach $dev (sort {$a <=> $b} keys %devices) {
+	printf "  Device 0x%04x occurs $devices{$dev} times.\n", $dev;
     }
 }
 
+## check field values
+
+# returns a warning message if $field isn't a valid string representation
+# of an integer, or if the resulting integer is out of the specified range
+sub validate_integer_field ($$$$) {
+    my $field = shift;
+    my $field_name = shift;
+    my $min = shift;
+    my $max = shift;
+
+    my $msg = "";
+
+    if ( not $field =~ /^-?\d+$/ ) { 
+	$msg = "      $field_name value contains invalid characters: \"$field\"\n";
+    } else {  
+	if ( $field < $min ) {
+	    $msg = "      $field_name value too low: \"$field\" < $min \n";
+        } elsif ( $field > $max ) {
+	    $msg = "      $field_name value too high: \"$field\" > $max \n";
+        } 
+    } 
+    return $msg;
+}
+
+
+# This routine loops through each directory entry in the $info data
+# structure and prints a warning message if tar would abort with an
+# "Unexpected field value in snapshot file" error upon reading this
+# snapshot file.
+#
+# (Note that this specific error message was introduced along with the
+# change to snapshot file format "2", starting with tar v1.16 [or,
+# more precisely, v1.15.91].)
+#
+# The checks here are intended to match those found in the incremen.c
+# source file (as of tar v1.16.1).  
+#
+# In that code, the checks are done against pre-processor expressions,
+# as defined in the C header files at compile time.   In the routine
+# below, a Perl variable is created for each expression used as part of
+# one of these checks, assigned the value of the related pre-processor
+# expression as found on a Linux 2.6.8/i386 system.  
+#
+# It seems likely that these settings will catch most invalid
+# field values found in actual snapshot files on all systems.  However,
+# if "tar" is erroring out on a snapshot file that this check routine
+# does not complain about, that probably indicates that the values
+# below need to be adjusted to match those used by "tar" in that
+# particular environment.
+#
+# (Note: the checks here are taken from the code that processes
+# version 2 snapshot files, but to keep things simple we apply those
+# same checks to files having earlier versions -- but only for 
+# the fields that actually exist in those input files.)
+
+sub check_field_values ($) {
+    my $info = shift;
+
+    # set up a variable with the value of each pre-processor 
+    # expression used for field-value checks in incremen.c 
+    # (these values here are from a Linux 2.6.8/i386 system) 
+    my $BILLION = 1000000000;        # BILLION
+    my $MIN_TIME_T = -2147483648;    # TYPE_MINIMUM(time_t)
+    my $MAX_TIME_T = 2147483647;     # TYPE_MAXIUMUM(time_t)
+    my $MAX_DEV_T = 4294967295;      # TYPE_MAXIUMUM(dev_t)
+    my $MAX_INO_T = 4294967295;      # TYPE_MAXIUMUM(ino_t)
+
+
+    my $msg;
+    my $error_found = 0;
+
+    print "  Checking field values in snapshot file...\n";
+
+    $snapver = $info->[0];
+
+    $msg = "";
+    $msg .= validate_integer_field($info->[1],
+	                   'timestamp_sec', $MIN_TIME_T, $MAX_TIME_T);
+    if ($snapver >= 1) {
+      $msg .= validate_integer_field($info->[2],
+	                   'timestamp_nsec', 0, $BILLION-1);
+    } 
+    if ( $msg ne "" ) {
+        $error_found = 1;
+	print "\n    shapshot file header:\n";
+	print $msg;
+    }
+
+
+    foreach my $dir (@{$info->[3]}) {
+
+	$msg = "";
+
+	$msg .= validate_integer_field($dir->{'nfs'}, 'nfs', 0, 1);
+        if ($snapver >= 1) {
+  	  $msg .= validate_integer_field($dir->{'timestamp_sec'},
+	                   	'timestamp_sec', $MIN_TIME_T, $MAX_TIME_T);
+	  $msg .= validate_integer_field($dir->{'timestamp_nsec'},
+	                   	'timestamp_nsec', 0, $BILLION-1);
+	}
+	$msg .= validate_integer_field($dir->{'dev'}, 'dev', 0, $MAX_DEV_T);
+	$msg .= validate_integer_field($dir->{'ino'}, 'ino', 0, $MAX_INO_T);
+
+	if ( $msg ne "" ) {
+          $error_found = 1;
+	  print "\n    directory: $dir->{'name'}\n";
+	  print $msg;
+	}
+    }
+
+    print "\n  Snapshot field value check complete" ,
+           $error_found ?  "" : ", no errors found" , 
+           ".\n";
+}
+
 ## editing
 
 sub replace_device_number ($@) {
     my $info = shift(@_);
     my @repl = @_;
 
-    foreach my $dir (@{${@$info}[3]}) {
+    my $count = 0;
+
+    foreach my $dir (@{$info->[3]}) {
         foreach $x (@repl) {
-	    if (${%$dir}{'dev'} eq $$x[0]) {
-	        ${%$dir}{'dev'} = $$x[1];
+	    if ($dir->{'dev'} eq $$x[0]) {
+	        $dir->{'dev'} = $$x[1];
+                $count++;
                 last;
             }
 	}
     }
+    print "  Updated $count records.\n"
 }
 
 ## writing
@@ -211,14 +372,17 @@ sub write_incr_db ($$) {
 sub write_incr_db_0 ($$) {
     my $info = shift;
     my $file = shift;
-
+    
     my $timestamp_sec = $info->[1];
     print $file "$timestamp_sec\n";
 
-    foreach my $dir (@{${@$info}[3]}) {
-	print $file "${%$dir}{'dev'} ";
-	print $file "${%$dir}{'ino'} ";
-	print $file "${%$dir}{'name'}\n";
+    foreach my $dir (@{$info->[3]}) {
+        if ($dir->{'nfs'}) {
+          print $file '+'
+        }
+	print $file "$dir->{'dev'} ";
+	print $file "$dir->{'ino'} ";
+	print $file "$dir->{'name'}\n";
     }
 }
 
@@ -226,19 +390,22 @@ sub write_incr_db_0 ($$) {
 sub write_incr_db_1 ($$) {
     my $info = shift;
     my $file = shift;
-
-    print $file "GNU tar-1.15-1\n";
+    
+    print $file $info->[4];
 
     my $timestamp_sec = $info->[1];
     my $timestamp_nsec = $info->[2];
     print $file "$timestamp_sec $timestamp_nsec\n";
 
-    foreach my $dir (@{${@$info}[3]}) {
-	print $file "${%$dir}{'timestamp_sec'} ";
-	print $file "${%$dir}{'timestamp_nsec'} ";
-	print $file "${%$dir}{'dev'} ";
-	print $file "${%$dir}{'ino'} ";
-	print $file "${%$dir}{'name'}\n";
+    foreach my $dir (@{$info->[3]}) {
+        if ($dir->{'nfs'}) {
+          print $file '+'
+        }
+	print $file "$dir->{'timestamp_sec'} ";
+	print $file "$dir->{'timestamp_nsec'} ";
+	print $file "$dir->{'dev'} ";
+	print $file "$dir->{'ino'} ";
+	print $file "$dir->{'name'}\n";
     }
 }
 
@@ -246,22 +413,22 @@ sub write_incr_db_1 ($$) {
 sub write_incr_db_2 ($$) {
     my $info = shift;
     my $file = shift;
-
-    print $file "GNU tar-1.16-2\n";
+    
+    print $file $info->[4];
 
     my $timestamp_sec = $info->[1];
     my $timestamp_nsec = $info->[2];
     print $file $timestamp_sec . "\0";
     print $file $timestamp_nsec . "\0";
 
-    foreach my $dir (@{${@$info}[3]}) {
-	print $file ${%$dir}{'nfs'} . "\0";
-	print $file ${%$dir}{'timestamp_sec'} . "\0";
-	print $file ${%$dir}{'timestamp_nsec'} . "\0";
-	print $file ${%$dir}{'dev'} . "\0";
-	print $file ${%$dir}{'ino'} . "\0";
-	print $file ${%$dir}{'name'} . "\0";
-	foreach my $dirent (@{${%$dir}{'dirents'}}) {
+    foreach my $dir (@{$info->[3]}) {
+	print $file $dir->{'nfs'} . "\0";
+	print $file $dir->{'timestamp_sec'} . "\0";
+	print $file $dir->{'timestamp_nsec'} . "\0";
+	print $file $dir->{'dev'} . "\0";
+	print $file $dir->{'ino'} . "\0";
+	print $file $dir->{'name'} . "\0";
+	foreach my $dirent (@{$dir->{'dirents'}}) {
 	    print $file $dirent . "\0";
 	}
 	print $file "\0";
@@ -271,9 +438,10 @@ sub write_incr_db_2 ($$) {
 ## main
 
 sub main {
-    our ($opt_b, $opt_r, $opt_h);
-    getopts('br:h');
-    HELP_MESSAGE() if ($opt_h || $#ARGV == -1 || ($opt_b && !$opt_r));
+    our ($opt_b, $opt_r, $opt_h, $opt_c);
+    getopts('br:hc');
+    HELP_MESSAGE() if ($opt_h || $#ARGV == -1 || ($opt_b && !$opt_r) ||
+                       ($opt_r && $opt_c) );
 
     my @repl;
     if ($opt_r) {
@@ -292,22 +460,38 @@ sub main {
 
 	    replace_device_number($info, @repl);
 	    write_incr_db($info, $snapfile);
+	} elsif ($opt_c) {
+	    check_field_values($info);
 	} else {
-	    show_device_counts($info, $snapfile);
+	    show_device_counts($info);
 	}
     }
 }
 
 sub HELP_MESSAGE {
-    print "Usage: tar-snapshot-edit.pl [-r 'DEV1-DEV2[,DEV3-DEV4...]' [-b]] SNAPFILE [SNAPFILE [..]]\n";
-    print "\n";
-    print "  Without -r, summarize the 'device' values in each SNAPFILE.\n";
-    print "\n";
-    print "  With -r, replace occurrences of DEV1 with DEV2 in each SNAPFILE.\n";
-    print "  DEV1 and DEV2 may be specified in hex (e.g., 0xfe01), decimal (e.g.,\n";
-    print "  65025), or MAJ:MIN (e.g., 254:1).  To replace multiple occurrences,\n";
-    print "  separate them with commas.  If -b is also specified, backup\n";
-    print "  files (ending with '~') will be created.\n";
+    print <<EOF;
+
+Usage:
+  tar-snapshot-edit SNAPFILE [SNAPFILE [...]]
+  tar-snapshot-edit -r 'DEV1-DEV2[,DEV3-DEV4...]' [-b] SNAPFILE [SNAPFILE [...]]
+  tar-snapshot-edit -c SNAPFILE [SNAPFILE [...]]
+
+     With no options specified: print a summary of the 'device' values 
+     found in each SNAPFILE.
+
+     With -r: replace occurrences of DEV1 with DEV2 in each SNAPFILE.
+     DEV1 and DEV2 may be specified in hex (e.g., 0xfe01), decimal (e.g.,
+     65025), or MAJ:MIN (e.g., 254:1).  To replace multiple occurrences,
+     separate them with commas.  If -b is also specified, backup files
+     (ending with '~') will be created.
+
+     With -c: Check the field values in each SNAPFILE and print warning
+     messages if any invalid values are found.  (An invalid value is one
+     that would cause \"tar\" to generate an 
+         Unexpected field value in snapshot file 
+     error message as it processed the snapshot file.)
+
+EOF
     exit 1;
 }