UNIX for Dummies Questions & Answers

Since the value of $file is states why isn't the output simply:

Visit beautiful states

from

Code:

done < "$file"

This means the the input from the file whose name is in the variable $file gets fed into the loop as stdin, so that read can process it and put the content of a line in variable state at every iteration..

Ok, but the original example does not contain that.

So how is it working?

is the variable name file special or would this work with any named variable?

The variable is just a variable.

In the example it says

Code:

for state in ‘cat $file’

which is not good practice in my opinion (what text book is this?), and again it has the wrong kind of quotes. It should read

Code:

for state in `cat $file`

Here cat extract the contents and "for" will go over them one by one.

This will work for the given sample, but only because the author cleverly left out a state like New Jersey. Watch what happens when you add that to the file...
There are ways to get around that, but fpmurphy's approach is much preferred, and is best practice.

Thank you for the reply.

The quotation issue is because I copy and pasted, please forgive that issue.

I have a better way to ask my question!

How does the command for know to extract the file named in the variable and not the string itself? I know its doing that, but just curious WHY and HOW If you just test `cat $file` you indeed get states so I'm assuming your reference to the "done" tells the command to extract the file if it exists?

The book is Linux Command Line and Scripting Bible by Richard Blum.

Indeed the next section does cover the issue of New Jersey and introduces the while command and the IFS variable but I have not gotten to that section yet! I hate to move forward not understanding this example in detail...

The command for doesn't "know". The shell first expands the variable $file so that it becomes:

Code:

for state in `cat states`

and then `cat states` gets expanded, so that the command becomes:

Code:

for state in Alabama Alaska Arizona Arkansas Colorado Connecticut Delaware Florida Georgia New Jersey
do

So now you know why this construction would not go well for New Jersey

Oh my GOD!

How did I miss that

I am extremely embarrassed seriously.

Thank you for your patience.