Study Notes

1.Double quotation “” is able to quota every strings except of back slash””, back quotation”`”(located nearby 1/! on the keyboard),and dollar”$” character.

2.Single quotation” could quota any strings including “,`$”.

3.Back quotation“,set the system output to variable. what was contain in pairs of “ will be issued as command. for example:
# echo ‘hello’ (single quotation)
hello
# echo `hello`
bash: hello: command no found
# echo `date`
2006年05月09日 星期二 (In my mandriva)
# mydate=`date`
# echo $mydate

How many users are logging on the system:
# echo “there is `who |wc-l` user in the system”

4.Back slash””: convertion
# echo *
it will list all the directy
# echo *
*
# echo “$99.99”
99.99
# echo “$99.99”
$99.99