Computing

Quick and Easy Debugging in Python

Submitted by Jeet Sukumaran on

I am afraid that in practice I have always ended up going the simple "litter the code with print statements" route when debugging my Python. Without the compilation step, the cost of inserting and then removing these lines from the source code is relatively cheap, and has served me well enough so far.

BASH function to return the absolute path of a file (or directory) name passed as an argument

Submitted by Jeet Sukumaran on

For some reason, a portable solution (i.e., something that works on most common flavors of POSIX systems, from the Linux variety to the Unix ones) to this is a little tricky.

Here is one that seems to do the job:

get_abs_path() {
    local PARENT_DIR=$(dirname "$1")
    cd "$PARENT_DIR"
    local ABS_PATH="$(pwd)"/"$(basename $1)"
    cd - >/dev/null
    echo $ABS_PATH
}

Boosting Interactive Bash Efficiency Through History Search/Completion/Editing

Submitted by Jeet Sukumaran on

Most of us know about using the bang operator (`!`) to recall an entry from our bash history:

$ ! # repeat last command
$ !22 # repeat command 22

You can use "!:" followed by a number to substitute in arguments from previous commands. So, for example, to run the command "dosomething" on the first argument of the previous command:

Locally Mounting a Remote Directory through a Firewall Gateway on OS X

Submitted by Jeet Sukumaran on

  1. Download and install MacFUSE.
  2. Download the sshfs binary, renaming/moving to, for example, "/usr/local/bin/sshfs".
  3. Create a wrapper tunneling script and save it to somewhere on your system path (e.g., "/usr/local/bin/ssh-tunnel-gateway.sh"), making sure to set the executable bit ("chmod a+x"): 
    #!

Filter for Unique Lines (Adjacent or Otherwise) While Preserving Original Order

Submitted by Jeet Sukumaran on

There are two BASH utilities that help you filter input for unique lines: 'uniq' and 'sort': One gotcha with 'uniq' is that it only filters out duplicate adjacent lines. So if your input looks like:

apple
apple
apple
chicory
chicory
chicory
banana
banana

Then running 'uniq' on it will yield:

apple
chicory
banana

But if the input has non-adjacent duplicate lines:

Ensuring that SGE Does not Oversubscribe Processors or Memory

Submitted by Jeet Sukumaran on

SGE, be default, will happily oversubscribe processors when multiple queues target the same nodes (nice one, SGE). Furthermore, even if jobs specify a memory limit, if each individual job uses less then the total memory limit, but the sum memory usage of jobs assigned to the machine exceeds the machine's memory, the memory of the entire node can be exhausted, sending it off into limbo (cunning, SGE, very cunning). The solution to both of these issues is to specify processors and memory as consumable resources at the host level. This post details the procedure.

Setting Up Git's difftool to Use Your Diff Viewer/Editor of Choice

Submitted by Jeet Sukumaran on

Git offers two ways of viewing differences between commits, or between commits and your working tree: diff and difftool. The first of these, by default, dumps the results to the standard output. This mode of presentation is great for quick summaries of small sets of changes, but is a little cumbersome if there are a large number of changes between the two commits being compared and/or you want to closely examin

Vim: Making those Arrow Keys Work With You (or Why the Anti-Arrow-Key Propaganda is Wrong ... )

Submitted by Jeet Sukumaran on

The Great Controversy

A standard dictum amongst experienced Vim users is not to use the arrow keys to move around your document. This dictum is often repeated again and again, in tones that range from the taken-for-granted to hysterical-zeal. The most common reason given for this is that using the arrow keys takes your hands away from the home row of your keyboard, and thus is wasteful both in terms of time and energy, whereas the standard Vim movement keys --- `h`, `j`, `k`, and `l` --- keep your hands on the home row, and therefore is far more efficient. Here is what I have discovered: this anti-arrow key argument is wrong!

Vim Regular Expression Special Characters: To Escape or Not To Escape

Submitted by Jeet Sukumaran on

Vim's regular expression dialect is distinct from many of the other more popular ones out there today (and actually predates them). One of the dialect differences that always leaves me fumbling has to do with which special characters need to be escaped. Vim does have a special "very magic" mode (that is activated by "\v" in the regular expression) that makes thing very clean and simple in this regard: only letters, numbers and underscores are treated a

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