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Count number of hits per IP address in last 2000 lines of apache logs and print the IP and hits if hits > 20

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Calculating series with awk: add numbers from 1 to 100
"seq 100" outputs 1,2,..,100, separated by newlines. awk adds them up and displays the sum. "seq 1 2 11" outputs 1,3,..,11. Variations: 1+3+...+(2n-1) = n^2 $ seq 1 2 19 | awk '{sum+=$1} END {print sum}' # displays 100 1/2 + 1/4 + ... = 1 $ seq 10 | awk '{sum+=1/(2**$1)} END {print sum}' # displays 0.999023

list block devices
Shows all block devices in a tree with descruptions of what they are.

Make vim open in tabs by default (save to .profile)
I always add this to my .profile rc so I can do things like: "vim *.c" and the files are opened in tabs.

Random number generation within a range N, here N=10

delete multiple files with spaces in filenames (with confirmation)
ls -Q will show the filenames in quotes. xargs -p rm will print all the filenames piped from ls -Q and ask for confirmation before deleting the files. without the -Q switch, if we have spaces in names, then the files won't be deleted.

Find the process you are looking for minus the grepped one
faster ;) but your idea is really cool

LDAP search to query an ActiveDirectory server
These are the parameters to ldapsearch (from ldap-utils in Ubuntu), for searching for the record for Joe Blogg's user. sAMAccountName is the LDAP field that ActiveDirectory uses to store the user name. 'DOMAIN\Joe.Bloggs' where "DOMAIN" is the the active directory domain. Othewise you could use "CN=Joe.Bloggs,DC=example,DC=com" instead of "DOMAIN\Joe.Bloggs"

Backup your hard drive with dd
This will create an exact duplicate image of your hard drive that you can then restore by simply reversing the "if" & "of" locations. $ sudo dd if=/media/disk/backup/sda.backup of=/dev/sda Alternatively, you can use an SSH connection to do your backups: $dd if=/dev/sda | ssh user@ssh.server.com dd of=~/backup/sda.backup


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