Meaning of certain commands in script?

SlowCoder · 10-12-2007, 07:51 AM

Suppose the following script.

Code:

cat myfile | \
while read strLine
do
set -- $strLine
echo $strLine
done

I would like to know the function of the highlighted parts?
I would also like to know when to, and when not to, use the $ in relation to script variables?

Tischbein · 10-12-2007, 09:48 AM

Code:

cat myfile | \ <---- the backslash is a linebreak, so the cat
                           is piping into the while statement.

while read strLine
do
set -- $strLine  <----- sets the $* variable to the lines one at a time,
                        so $1 is set to the first word in the line,
                        $2 to the second and so on.

echo "________________"
echo '$* == ' $*
echo '$1 == ' $1 '  $2 == ' $2

echo $strLine

done

SlowCoder · 10-12-2007, 11:21 AM

Excellent explanation! Thank you.

For clarification, I don't actually need to use set -- $strLine in the example I gave, assuming I just want to display the entire string value? So, really the set line is extraneous?

Can you also answer my 2nd question, regarding when to use the $ symbol? From what I can tell, you don't have to use it when setting a value to a variable, but should use it when getting a value from the same variable?