Merge pull request #73 from katrinleinweber/useful-file-names

Improve filename examples & re-iterate use of $(date)

_episodes/05-counting-mining.md

@@ -529,11 +529,11 @@ $ grep -i revolution *.tsv
 {: .bash}
 
 This script looks in the defined files and prints any lines containing `revolution`
-(without regard to case) to the shell. We add today's date to the filename using
-[ISO format](https://en.wikipedia.org/wiki/ISO_8601) of `YYYY-MM-DD`.
+(without regard to case) to the shell. We let the shell add today's date to the
+filename:
 
 ~~~
-$ grep -i revolution *.tsv > results/2016-07-19_JAi-revolution.tsv
+$ grep -i revolution *.tsv > results/$(date -I)_JAi-revolution.tsv
 ~~~
 {: .bash}
 
@@ -546,7 +546,7 @@ Thankfully, the `-w` flag instructs `grep` to look for whole words only,
 giving us greater precision in our search.
 
 ~~~
-$ grep -iw revolution *.tsv > results/2016-07-19_JAiw-revolution.tsv
+$ grep -iw revolution *.tsv > results/$(date -I)_JAiw-revolution.tsv
 ~~~
 {: .bash}
 
@@ -567,6 +567,17 @@ $ wc -l results/*.tsv
 ~~~
 {: .output}
 
+> ## Automatically adding a date prefix
+> Notice how we didn't type the `YYYY-MM-DD` date ourselves, but let
+> `date -I` do that mindless task for us. Find out about this option
+> and the standard format that it uses.
+> 
+> > ## Solution
+> > Using `date --help` will show you that `-I` is short for [--iso-8601](https://en.wikipedia.org/wiki/ISO_8601), which essentially avoids the confusion between the European
+> > and American date formats `DD.MM.YYYY` and `MM/DD/YYYY`.
+> {: .solution}
+{: .challenge}
+
 Finally, we'll use the **regular expression syntax** covered earlier to search for similar words.
 
 > ## Basic and extended regular expressions
@@ -661,23 +672,23 @@ Pair up with your neighbor and work on these exercises:
 
 > ## Case insensitive search in select files
 > Search for all case insensitive instances of that
-> word in the 'America' and 'Africa' `.tsv` files in this directory. Print your results to  a file `results/new.tsv`.
+> word in the 'America' and 'Africa' `.tsv` files in this directory. Print your results to  a file `results/hero.tsv`.
 >
 > > ## Solution
 > > ~~~
-> > $ grep -i hero *a.tsv > results/new.tsv
+> > $ grep -i hero *a.tsv > results/hero.tsv
 > > ~~~
 > > {: .bash}
 > {: .solution}
 {: .challenge}
 
 > ## Case insensitive search in select files (whole word)
 > Search for all case insensitive instances of that whole word
-> in the 'America' and 'Africa' `.tsv` files in this directory. Print your results to a file `results/new2.tsv`.
+> in the 'America' and 'Africa' `.tsv` files in this directory. Print your results to a file `results/hero-i.tsv`.
 >
 > > ## Solution
 > > ~~~
-> > $ grep -iw hero *a.tsv > results/new2.tsv
+> > $ grep -iw hero *a.tsv > results/hero-i.tsv
 > > ~~~
 > > {: .bash}
 > {: .solution}