Phly, boy, phly
the weblog and site of Matthew Weier O'Phinney

One thing I noticed today when using RCS is that it isn't terribly user friendly -- you need to checkout a file to make edits. Often, I make edits, and then want to commit my changes.

So I wrote a wrapper script called revise. It makes a temporary copy of the file you've been editing, checks it out of RCS with locking, makes it writeable, moves the temporary copy to the permanent name, checks it in and unlocks it (which prompts for a log message), and then makes the file writeable for the user and group again. The script is outlined here:

    #!/bin/bash
    FILE=$1
    cp $FILE $FILE.new
    co -l $FILE
    chmod u+w $FILE
    mv $FILE.new $FILE
    ci -u $FILE
    chmod ug+w $FILE

Being the ROX-Filer centric person I am, I also wrote a quick perl script called rox-revise that I can then put in my SendTo menu. It parses the file's path, changes to that directory, and then calls the revise script on the filename, from within a terminal. This script follows:

    #!/usr/bin/perl -w
    use strict;

    use vars qw/$path $file $TERMCMD $REVISE $ZENITY/;

    # Configurable variables
    $TERMCMD = "myTerm";    # What terminal command to use; must be xterm compliant
    $REVISE  = "revise";    # What command to use to revise (i.e. rcs ci) the file
    $ZENITY  = "zenity";    # The zenity or dialog or xdialog command to use

    # Grab the filename from the command line
    $path = shift;
    $file = $path;

    # If no file given, raise a dialog and quit
    if (!$path || ($path eq '')) {
        system(
            $ZENITY, 
            '--title=Error', 
            '--warning', 
            "--text=No path given to $0; rox-revise quit!"
        );
        exit 0;
    }

    # Get the path to the file and switch to that directory
    if ($path =~ m#/#) {
        $path =~ s#^(.*)/.*?$#$1#;
        if ($path !~ m#^/#) { $path = "./$path"; }
        chdir $path or die "$path not found!n";
    } else {
    # Or else assume we're in the current directory
        $path = './';
    }

    # Get the filename
    $file =~ s#^.*/(.*?)$#$1#;

    # Execute the revise statement
    my $failure = system($TERMCMD, '-e', $REVISE, $file);
    if ($failure) {
        # on failure, raise a dialog
        system(
            $ZENITY, 
            '--title=Error', 
            '--warning', 
            "--text=Unable to revise $file"
        );
    }

    1;

Now I just need to check out Subversion, and I can have some robust versioning!

In trying to implement some of the hacks in Linux Server Hacks, I had to go to the ssh manpage, where I discovered a number of cool tricks.

1. In order to get key-based authentication (i.e., passwordless) working, the $HOME/.ssh directory must be mode 0700, and all files in it must be mode 0600. Once that's setup properly, key-based authentication works perfectly.
2. You can have a file called config in your $HOME/.ssh directory that specifies user-specific settings for using SSH, as well as a number of host-specific settings:
   • Compression yes turns on compression
   • ForwardX11 yes turns on X11 forwarding by default
   • ForwardAgent yes turns on ssh-agent forwarding by default
   • Host-based settings go from one Host keyword to the next, so place them at the end of the file. Do it in the following order:

         Host nickname
         HostName actual.host.name
         User username_on_that_host
         Port PortToUse
                 

     This means, for instance, that I can ssh back and forth between home using the same key-based authentication and the same ssh-to script (more below) I use for work servers -- because I don't have to specify the port or the username.

I mentioned a script called ssh-to earlier. This is a neat little hack from the server hacks book as well. Basically, you have the following script in your path somewhere:

    #!/bin/bash
    ssh -C `basename $0` $*

Then, elsewhere in your path, you do a bunch of ln -s /path/to/ssh-to /path/to/$HOSTNAME, where $HOSTNAME is the name of a host to which you ssh regularly; this is where specifying a host nickname in your $HOME/.ssh/config file can come in handy. Then, to ssh to any such server, you simply type $HOSTNAME at the command line, and you're there!

Gleaned from Linux Server Hacks

• Create an RCS directory
• Execute a 'ci -i filename'
• Execute a 'co -l filename' and edit as you wish.
• Execute a 'ci -u filename' to check in changes.

The initial time you checkout the copy, it will be locked, and this can cause problems if someone else wishes to edit it; you should probably edit it once and put in the version placeholder in comments somewhere at the top or bottom:

$VERSION$

and then check it back in with the -u flag to unlock it.