As always with Linux, there’s a plethora of ways to do what I am doing below, so this is just an example for your reference:

function check_mounted () {
    local result=`df | grep $1`
    echo $((${#result} > 0 ? 1 : 0))
}

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1. Relative path to absolute path in a bash shell.
2. Handy command line currency converter.
3. Masking fixed length strings in PHP.

$ pwd
/media/usbdisk/bin

$ readlink -f ./../mnt/.Skype
/media/usbdisk/mnt/.Skype

When you use readlink in a script and assign a resulting path to a variable, you should add the n flag (-fn) to suppress the trailing newline.

As you might have noticed, I needed to use this in a script to launch Skype but specify that I want to use the data files on my usb key as opposed to the default ~/.Skype location. This however was not working with relative paths and Skype would crash with something like:

$ FatalAssert(*out_ptr != ‘.’ && !strstr(out_ptr, “../”) && !strstr(out_ptr, “..\\”))
FatalAssert(*out_ptr != ‘.’ && !strstr(out_ptr, “../”) && !strstr(out_ptr, “..\\”))

The moment I pass a real path to Skype’s –dbpath parameter, everything works as expected.

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1. Ternary operator for bash scripting.
2. Automatically download and merge multiple PDF files with a Unix shell.
3. How to install KDE on Fedora Core 13 and onwards.

At the time, I did this hoping that in a worse-case-scenario, a maximum of 2 sources would die in any weekend. Luckily, the sources lasted for the 3 years whilst I was working for that company (and apparently for another two after that). Now, I hear, they are manually updating a static text file… once in a while.

Today, I have no such needs but as always I am constantly looking for new ways to do things, should the need arise. I also needed a simple currency converter for doing small calculations like how much to top up a prepaid credit card by to purchase something from eBay which is listed in another currency.

Full credits to rafacas at commandliners for the inspiration and as he points out, note that the script uses Google Finance’s page.

#!/bin/bash

# 2009 - Rafa Casado - http://bit.ly/bYZwex
# 2010 - Chris Ergatides - http://bit.ly/9XjAUz

if [ $# -lt 2 ]; then
    echo -e "\nUsage: $0 currency1 currency2 amount"
    echo "Default: $0 GBP EUR 1"
    echo "Example 1: $0 USD GBP"
    echo "Example 2: $0 GBP USD 42"
fi

toUpper() {
    echo $@ | tr "[:lower:]" "[:upper:]"
}

if [ -n "$1" ]; then FROM=$(toUpper "$1"); else FROM=GBP; fi
if [ -n "$2" ]; then TO=$(toUpper "$2"); else TO=EUR; fi
if [ $TO == $FROM ]; then echo 'Nothing to do!'; exit 2; fi
if [ -n "$3" ]; then A=$3; else A=1; fi

CONVERTER="http://www.google.com/finance/converter?a=$A&from=$FROM&to=$TO"

RESULT=`wget -nv -O - "$CONVERTER" 2>&1 | \
sed -n -e 's/.*<span class=bld>\(.*\)<\/span>.*/\1/p'`

echo -e "\nResult: $A $FROM = $RESULT\n"

So, let’s say you’ve named the script currency.sh and made it executable with chmod +x, what does the output look like?

#Called without any parameters:
[chris@r500 ~/bin]$ ./currency.sh

Usage: /home/chris/bin/currency.sh currency1 currency2 amount
Default: /home/chris/bin/currency.sh GBP EUR 1
Example 1: /home/chris/bin/currency.sh USD GBP
Example 2: /home/chris/bin/currency.sh GBP USD 42

Result: 1 GBP = 1.1387 EUR

#Called with example 1's parameters:
[chris@r500 ~/bin]$ ./currency.sh usd gbp

Result: 1 USD = 0.6475 GBP

#Called with example 2's parameters
[chris@r500 ~/bin]$ ./currency.sh gbp usd 42

Result: 42 GBP = 64.8606 USD

Related posts:

1. What’s my IP? Check your IP address from the command line.
2. Ternary operator for bash scripting.
3. Using sed to search and replace contents of next line in a file.