From 8f6d8b05152fda68e0c01848c0e5239e0093548a Mon Sep 17 00:00:00 2001 From: Richard Jones Date: Sun, 11 Jul 2010 16:46:15 +0100 Subject: [PATCH] edit: Add -e 'expr' option to non-interactively apply expression to the file. (Suggested by Justin Clift). --- tools/virt-edit | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 125 insertions(+), 15 deletions(-) diff --git a/tools/virt-edit b/tools/virt-edit index e00e4cf..d4e11db 100755 --- a/tools/virt-edit +++ b/tools/virt-edit @@ -1,6 +1,6 @@ #!/usr/bin/perl -w # virt-edit -# Copyright (C) 2009 Red Hat Inc. +# Copyright (C) 2009-2010 Red Hat 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 @@ -40,6 +40,8 @@ virt-edit - Edit a file in a virtual machine virt-edit [--options] disk.img [disk.img ...] file + virt-edit [domname|disk.img] file -e 'expr' + =head1 WARNING You must I use C on live virtual machines. If you do @@ -56,10 +58,18 @@ cases you should look at the L tool. =head1 EXAMPLES +Edit the named files interactively: + virt-edit mydomain /boot/grub/grub.conf virt-edit mydomain /etc/passwd +You can also edit files non-interactively (see +L below). +To change the init default level to 5: + + virt-edit mydomain /etc/inittab -e 's/^id:.*/id:5:initdefault:/' + =head1 OPTIONS =over 4 @@ -92,6 +102,19 @@ connect to the default libvirt hypervisor. If you specify guest block devices directly, then libvirt is not used at all. +=cut + +my $expr; + +=item B<--expr EXPR> | B<-e EXPR> + +Instead of launching the external editor, non-interactively +apply the Perl expression C to each line in the file. +See L below. + +Be careful to properly quote the expression to prevent it from +being altered by the shell. + =back =cut @@ -99,6 +122,7 @@ at all. GetOptions ("help|?" => \$help, "version" => \$version, "connect|c=s" => \$uri, + "expr|e=s" => \$expr, ) or pod2usage (2); pod2usage (1) if $help; if ($version) { @@ -139,33 +163,117 @@ my $root_dev = $roots[0]; my $os = $oses->{$root_dev}; mount_operating_system ($g, $os, 0); -my ($fh, $tempname) = tempfile (); +my ($fh_not_used, $tempname) = tempfile (); # Allow this to fail in case eg. the file does not exist. $g->download($filename, $tempname); -my $oldctime = (stat ($tempname))[10]; +my $do_upload = $tempname; -my $editor = $ENV{EDITOR}; -$editor ||= "vi"; -system ("$editor $tempname") == 0 - or die "edit failed: $editor: $?"; +if (!defined $expr) { + # Interactively edit the file. + my $oldctime = (stat ($tempname))[10]; -my $newctime = (stat ($tempname))[10]; + my $editor = $ENV{EDITOR}; + $editor ||= "vi"; + system ("$editor $tempname") == 0 + or die "edit failed: $editor: $?"; -if ($oldctime != $newctime) { - $g->upload ($tempname, $filename) + my $newctime = (stat ($tempname))[10]; + + if ($oldctime == $newctime) { + $do_upload = undef; + print __"File not changed.\n"; + } } else { - print __"File not changed.\n"; + my ($fh, $tempout) = tempfile (); + + # Apply a Perl expression to the lines of the file. + open IFILE, $tempname or die "$tempname: $!"; + my $lineno = 0; + while () { + $lineno++; + eval $expr; + die if $@; + print $fh $_ or die "print: $!"; + } + close $fh; + + $do_upload = $tempout; } -$g->sync (); -$g->umount_all (); +if (defined $do_upload) { + $g->upload ($do_upload, $filename); + $g->umount_all (); + $g->sync (); +} undef $g; exit 0; +=head1 NON-INTERACTIVE EDITING + +C normally calls out to C<$EDITOR> (or vi) so +the system administrator can interactively edit the file. + +There are two ways also to use C from scripts in order to +make automated edits to files. (Note that although you I use +C like this, it's less error-prone to write scripts +directly using the libguestfs API and Augeas for configuration file +editing.) + +The first method is to temporarily set C<$EDITOR> to any script or +program you want to run. The script is invoked as C<$EDITOR tmpfile> +and it should update C in place however it likes. + +The second method is to use the C<-e> parameter of C to run +a short Perl snippet in the style of L. For example to +replace all instances of C with C in a file: + + virt-edit domname filename -e 's/foo/bar/' + +The full power of Perl regular expressions can be used (see +L). For example to delete root's password you could do: + + virt-edit domname /etc/passwd -e 's/^root:.*?:/root::/' + +What really happens is that the snippet is evaluated as a Perl +expression for each line of the file. The line, including the final +C<\n>, is passed in C<$_> and the expression should update C<$_> or +leave it unchanged. + +To delete a line, set C<$_> to the empty string. For example, to +delete the C user account from the password file you can do: + + virt-edit mydomain /etc/passwd -e '$_ = "" if /^apache:/' + +To insert a line, prepend or append it to C<$_>. However appending +lines to the end of the file is rather difficult this way since there +is no concept of "last line of the file" - your expression just +doesn't get called again. You might want to use the first method +(setting C<$EDITOR>) if you want to do this. + +The variable C<$lineno> contains the current line number. +As is traditional, the first line in the file is number C<1>. + +The return value from the expression is ignored, but the expression +may call C in order to abort the whole program, leaving the +original file untouched. + +Remember when matching the end of a line that C<$_> may contain the +final C<\n>, or (for DOS files) C<\r\n>, or if the file does not end +with a newline then neither of these. Thus to match or substitute +some text at the end of a line, use this regular expression: + + /some text(\r?\n)?$/ + +Alternately, use the perl C function, being careful not to +chomp C<$_> itself (since that would remove all newlines from the +file): + + my $m = $_; chomp $m; $m =~ /some text$/ + =head1 ENVIRONMENT VARIABLES =over 4 @@ -187,7 +295,9 @@ L, L, L, L, -L. +L, +L, +L. =head1 AUTHOR @@ -195,7 +305,7 @@ Richard W.M. Jones L =head1 COPYRIGHT -Copyright (C) 2009 Red Hat Inc. +Copyright (C) 2009-2010 Red Hat 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 -- 1.8.3.1