mjhjmtu

i am writing a bash script in which i am storing current date in a variable and then i am greping that variable . issue is its not working

currentdate= $(date +%b %d)
echo "$currentdate"
last |grep -E '$currentdate'>> /usr/IBM/HTTPServer7/logs/alert/users.txt

users.txt is showing empty . if i write mannualy the current date then it works
what am i doing wrong?

In addition to the quotes, you also need to account for the date format used by the last command, which looks like the following:

Dec 3 # Note the padding to the left of '3'.
Nov 23

This requires a slightly different date command:

date "+%b %_d"
Dec 4

The underscore instructs date to pad the field with spaces. You can also use %e as an alternative.

Putting these together, you can modify your script as shown below:

currentdate=$(date "+%b %_d")
last | grep "$currentdate" >> /usr/IBM/HTTPServer7/logs/alert/users.txt

@Sparhawk is correct.

Double quotes cause the shell to expand variables.

$ VAR=blahblah
$ echo "$VAR"
blahblah

Single quotes cause the shell to use the text literally.

$ VAR=blahblah
$ echo '$VAR'
$VAR

You would use this if you wanted to prevent the shell from thinking a dollar sign plus some other text was a variable.

echo 'This script is terminating because you didn't set $IMPORTANT_VARIABLE'

Without single quotes the above message wouldn't output properly.