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Writing a Bash script that knows its own location

I wrote a small bash script the other day, on Ubuntu, to launch a java program in a jar file. My first attempt worked, but it only worked if you invoked the script from the folder the script was in, but if it was invoked from any other folder, it would fail, because it was referencing the jar file with a relative path, and that path was relative of the location the script was invoked from, not the location it resided in.

Here's an example script:

#!/bin/bash
LSOF=$(lsof -p $$ | grep -E "/"$(basename $0)"$")
MY_PATH=$(echo $LSOF | sed -r s/'^([^\/]+)\/'/'\/'/1 2>/dev/null)
MY_ROOT=$(dirname $MY_PATH)
java -cp $MY_ROOT/../target/yourjar-1.0-SNAPSHOT-jar-with-dependencies.jar com.acme.YourClass

I did find one edge case where this doesn't work.. If the script is in a folder with the same name as the script, it gets messed up.

Filed under // bash howto java ubuntu

Using "citext" in PostgreSQL for case insensitive comparisons

I think its new in PostgreSQL 8.4, there is a new field type called citext, which stands for case insensitive text. Currently on Ubuntu 9.10 its in the PostgreSQL contrib package, which often serves as a testbed for features before they are adopted into PostgreSQL proper.

Using citext ensures that all comparisons are case insensitive, which includes referential integrity on inserts, updates and deletes, and SQL queries for lookups for example, which I think will work well for those fields that should always be compared case insensitive.

Although citext (and probably many other modules) are not listed on the contrib page, they are included, you can see them in the complete file list.

Steps to install on Ubuntu 9.10 (Karmic Koala):

# Install the contrib package
sudo apt-get install postgresql-contrib-8.4
# Add the citext module to a database of your choice
psql [username] -d [databaseName] -f /usr/share/postgresql/8.4/contrib/citext.sql

Where in this case /usr/share/postgresql/8.4 is the PostgreSQL SHARE_DIR folder.

Now you can use the field citext instead of text. If you'd like to use citext on Ubuntu 9.04 Jaunty (which only includes PostgreSQL 8.3), then check out Mark's post about installing PostgreSQL 8.4 on Ubuntu 9.04.

Filed under // howto linux postgres postgresql ubuntu

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Writing a Bash script that knows its own location

Using "citext" in PostgreSQL for case insensitive comparisons