Grep and Awk.

If you're getting tired, this would be a good place to quit. Grep and Awk are very useful tools but not entirely trivial for mere mortals to use.

GREP

Grep lets you search a file for a string pattern and then spews any lines that match the string anywhere to the screen. We can find thisline in this html file using:
grep thisline grep.html.

And get these results:
can find thisline in this html file using:

Grep has several switches but the two I find most useful are -i which makes it case insensitive and -v which says to find any line which doesn't match the pattern.

AWK

According to the man page, awk is a "pattern scanning and processing language," but I most often use it to chop a file into columns and pull out, rearrange, whatever to the results.

The date command lets you print today's date in a specified format such as:
/bin/date -u +%c%m%d
which gives: Tue Feb 06 15:49:52 20010206. (Use man date if you want to learn more).

Now to just get a date string use:
/bin/date -u +%c%m%d | /bin/awk '{print $5}'
which produces: 20010206. We used awk here to print only the fifth column of the output of date.

Now we can pipe this through julday to get the julian date:
/bin/date -u +%c%m%d | /bin/awk '{print $5}' | julday
which produces:
Calendar Date 02 06 2001
Julian Date 037 2001
We fed the fifth column of the output of date to the julday program.

Finally we can make a julian date string using:
/bin/date -u +%c%m%d | /bin/awk '{print $5}' | julday | grep Julian | awk '{print $4$3}'
resulting in:2001037. We fed the fifth column of the output of date to the julday program then printed the fourth and third columns of the results.

Had enough? I warned you to quit earlier.