Login Activity on a Unix Server

To check the login activity on a Unix server you can run the following command:
# last | head

'head' just displays the last 10 logins.

You can also check the login activity of a specific user:
# last user_name | head

Total Memory Installed on Solaris

Use the prtconf command to get the total amount of memory installed on a Solaris machine:
# prtconf

Counting the number of occurrences of each line in a file

To count the number of occurrences of each line in Linux you can use the following command:
sort input_file | uniq -c > output_file

You may want to ignore the case and then apply the count:
cat input_file | tr '[:upper:]' '[:lower:]' | sort | uniq -c > output_file

Removing punctuation from a file in Linux

To remove the punctuation from a file run the following command:
cat input_file | tr -d '[:punct:]' > output_file

Converting all Upper Case letters to Lower Case in Linux

To convert all upper case characters to lower case in Linux, run the following command:
cat input_file | tr '[:upper:]' '[:lower:]' > output_file