UNIX operating systems enforce strict access control of files based on the owner, a group, and everyone else. This document describes the techniques for setting these access controls with chmod. The UNIX chmod command can be confusing until a few basic points are explained. It allows different access control for the owner of the file [...]

# last filed zcat access.log.gz |grep 27/Jan/2008 |awk ‘{ field = $NF }; {print field}’ # count per Hits zcat access.log.gz  |grep 27/Jan/2008 |awk ‘{ field = $NF }; {print “Host: ” field } ‘ | sort |uniq -c # count per Hits + Totale al fondo cat nomefile |grep “27/Jan/2008:” |awk ‘ { field [...]

When variables are used they are referred to with the $ symbol in front of them. There are several useful variables available in the shell program. Here are a few: $$ = The PID number of the process executing the shell. $? = Exit status variable. $0 = The name of the command you used [...]