[mdlug] Extracting the day of the Week in BASH

[Daniel Hedlund]

Ingles, Raymond wrote:
>> From: Robert Adkins
> 
>>     Anyone know either the variable that returns the actual day of the 
>> week or a very short script to extract the day of the week?
> 
>  date | cut -d" " -f 1

Be careful about using "date" this way (or with +%a or +%A) to extract 
the day of the week if you're going to compare it against something.  I 
believe just running "date" will grab the date based on the current 
locale.  If your script might get run in an environment where the locale 
is set to another language, you could get something unexpected.  For 
example, if you're doing any comparisons in your script such as to only 
do something on Tuesday, you might write:

if [ "$(date +%A)" = "Tuesday" ]; then
     echo "today is Tuesday..."
fi

This could cause a problem if the locale returns the day of the week in 
a slightly different format.  In this circumstance, you would probably 
want to use +%u for extracting the day of the week as a number.  I 
believe this option is hard-coded to start on Monday irrespective of locale:

if [ $(date +%u) -eq 2 ]; then
     echo "today is Tuesday...";
fi

Let me know if I'm mistaken.

Cheers,

Daniel Hedlund
daniel at digitree.org