Computing

Vim's text objects are not only a powerful, flexible and precise way to specify a region of text, but also intuitive and efficient. They can be used with any command that can be combined with a motion (e.g., "d", "y", "v", "r"), but in this post I will be using the "c" command ("change") to illustrate them.

Vim continues to surprise me with its wonders. Sometimes (many times, in fact) things do not make sense, and I am perplexed as to the reasoning behind them. Then, one day, I grok it. And from that day on, I can never imagine any other way of doing it.

Here are some enhancements that I recently made to my Vim configuration that have revolutionized its power and ease-of-use when grepping for text across multiple buffers and files.

• Position the cursor over any word in an open, and (in normal mode, of course), type "*". This will jump you to the next occurrence of the word under the buffer. If search highlighting is turned on ("set hlsearch"), all occurrences of the word will be highlighted.
• Now type "#". This time, you will be taken back to the previous occurrence of the word under the cursor.
• Now type "[I".

Mounting the Volume on the Head Node

1. Create the directory on the head node on which the volume will be mounted:

           $ mkdir /work1
    

2. Add an entry to '/etc/fstab' that mounts the volume:

           /dev/sdc1   /work1      ext3        defaults    1 2
    

Serve the Mounted Volume using NFS

1. Add an entry to '/etc/exports' to allow NFS sharing of the volume:

           /work1 10.1.1.1(rw,async,no_root_squash) 10.1.0.0/255.255.

Mounting the Volume on the Head Node

1. Create the directory on the head node on which the volume will be mounted:

           $ mkdir /work1
    

2. Add an entry to '/etc/fstab' that mounts the volume:

           /dev/sdc1   /work1      ext3        defaults    1 2
    

Serve the Mounted Volume using NFS

1. Add an entry to '/etc/exports' to allow NFS sharing of the volume:

           /work1 10.1.1.1(rw,async,no_root_squash) 10.1.0.0/255.255.

This package looks promising:

PyMC: Bayesian Stochastic Modelling in Python

There is no way to get tar to ignore directory paths of files that it is archiving. So, for example, if you have a large number of files scattered about in subdirectories, there is no way to tell tar to archive all the files while ignoring their subdirectories, such that when unpacking the archive you extract all the files to the same location. You can, however, tell tar to strip a fixed number of elements from the full (relative) path to the file when extracting using the "--strip-components" option. For example:

In a previous post, I discuss a couple of approaches to dealing with the "Argument list too long" error when transferring large numbers of files. The solution to this problem is to archive the files, using the "-T" option of the "tar" command to pass in a list files generated by a "find" command:

1. Create a list of the files to be archived using the "find" command:

   $ find . -name="*.tre" > filelist.txt

2. Use the "-T" option of the "tar" command to pass in this list of filenames:

   $ tar cvjf archive.tbz -T filelist.txt

If you want to delete a long list of files, however, this approach will not work, as "rm" does not support the very convenient "-T"/"--files-from" flag or the equivalent (so convenient, in fact, that I have started adding this to virtually every file-processing script or program that I write).

Luckily, however, "find" does support a "-delete" flag, so to recursively delete all files and directories:

find path/to/dir -delete