A Better Expect Subversion Post-Commit Hook

In a previous post I wrote a small expect script to update a remote web server’s deployed code on a new commit to a Subversion repository using Expect and Subversion’s post-commit hooks. That first script was extraordinarily basic, so I’ve been wanting to add some sanity and error checking to it for a while. I finally got around to it today.

This improved version of the post-commit hook does the same thing as the last one (that is, it logs into your web server over SSH with the given user and password, and yes, I’m aware of the scariness of embedding a password in such a way, so you should really set up SSH to use public keys for authentication for this), except now it also produces useful output.

Here’s the same script as before, but improved:

#!/usr/bin/expect -f

#
# AUTHOR: Meitar Moscovitz
# DATE : Thu Jun 21 16:32:42 EDT 2007
#

set HOST my.web.server
set USER someuser
set PASS xxx

# the working copy we're going to update
set WC /path/to/working/copy

# the path to the svn executable on the remote web server
set SVNBIN /usr/local/bin/svn

# our network is slow, set a long timeout
set timeout 30

##### DO NOT EDIT PAST THIS LINE! #####

# POST-COMMIT HOOK
#
# The post-commit hook is invoked after a commit.  Subversion runs
# this hook by invoking a program (script, executable, binary, etc.)
# named 'post-commit' (this file) with the
# following ordered arguments:
#
#   [1] REPOS-PATH   (the path to this repository)
#   [2] REV          (the number of the revision just committed)
#
# Note that Subversion does not provide this program with an environment
# of any kind. That means this program lacks a current working directory,
# a home directory, a $PATH, and so on.

set REPOS [lindex $argv 0]
set REV [lindex $argv 1]

# Define error codes
set E_NO_SSH     1 ;# can't find a usable SSH on our system
set E_NO_CONNECT 2 ;# failure to connect to remote server (timed out)
set E_WRONG_PASS 3 ;# password provided does not work
set E_UNKNOWN   25 ;# unexpected failure

# find the SSH binary on our system
if {[file executable /usr/bin/ssh]} {
    set SSHBIN /usr/bin/ssh
} elseif {[file executable /usr/local/bin/ssh]} {
    set SSHBIN /usr/local/bin/ssh
} else {
    send_error "Can't find a usable SSH on this system.\n"
    exit $E_NO_SSH
}

spawn $SSHBIN $USER@$HOST $SVNBIN update $WC

expect {
    "continue connecting (yes/no)? " { send "yes\r"; exp_continue; }
    -nocase "password:" { send "$PASS\r"; }
    timeout {
        send_error "\nWe have timed out after $timeout seconds while trying to connect to $HOST!\n";
        exit $E_NO_CONNECT;
    }
}

expect {
    -nocase "password:" { ;# if we are asked for the password again, then we have provided the wrong password
        send_error "\nCan not log in to $HOST because the password provided for user $USER has been rejected.\n";
        exit $E_WRONG_PASS;
    }
    -re "revision (\[0-9]+)." {
        if {$REV == $expect_out(1,string)} {
            send_user "\nSuccessfully updated $WC on $HOST to revision $REV.\n"
        } else {
            send_user "\nUpdated repository to revision $expect_out(1,string), but svn reports that we are at revision number $REV.\n"
            send_error "CAUTION: Repository updated to revision $expect_out(1,string), but committed revision $REV.\n"
        }
    }
    default {
        send_error "An unexpected error has occured. The process at spawn ID $spawn_id has produced the following output:\n"
        send_error $expect_out(buffer)
        exit $E_UNKNOWN
    }
}

from: http://maymay.net/blog/2007/06/21/a-better-expect-subversion-post-commit-hook/

Found a way to get around the svn password prob.

spawn $SSHBIN $USER@$HOST -t “$SVNBIN update $WC -password $PASS2″