If the 'lm' flag is present, then the CPU is 64-bit.

If no output, then CPU is 32-bit.

From 'man netstat'

"netstat -i | -I interface [-abdnt] [-f address_family] [-M core] [-N system]

Show the state of all network interfaces or a single interface

which have been auto-configured (interfaces statically configured

into a system, but not located at boot time are not shown). An

asterisk (``*'') after an interface name indicates that the

interface is ``down''. If -a is also present, multicast

addresses currently in use are shown for each Ethernet interface

and for each IP interface address. Multicast addresses are shown

on separate lines following the interface address with which they

are associated. If -b is also present, show the number of bytes

in and out. If -d is also present, show the number of dropped

packets. If -t is also present, show the contents of watchdog

timers."

This is a nice way to kill processes.. the example here is for firefox!!! substitute firefox for whatever the process name is...

To save the result, redirect the output to another file.

convenience.

Useful to check DDoS attacks on servers.

Yet another ps grep function, but this one includes the column headings.

My variant on this common function. Some highlights:

Allows you to override the default ps args of "aux"

Uses bracket trick to omit the grep process itself without having to use a second grep

Always prints the correct header row of ps output

Limitations: Ugly ps error output if you forget to quote your multi word grep argument

This command takes the output of the 'last' command, removes empty lines, gets just the first field ($USERNAME), sort the $USERNAMES in reverse order and then gives a summary count of unique matches.

Searching for a String in Multiple Files With Grep

This will give you the Dell Service tag number associated with your machine. Incredibly useful when you need that number for tech support or downloads.

This command deletes all files in all subfolders if their name or path contains "deleteme".

To dry-run the command without actually deleting files run:

This is a 'killall' command equivalent where it is not available.

Prior to executing it, set the environment variable USERNAME to the username, whose processes you want to kill or replace the username with the $USERNAME on the command above.

Side effect: If any processes from other users, are running with a parameter of $USERNAME, they will be killed as well (assuming you are running this as root user)

[-9] in square brackets at the end of the command is optional and strongly suggested to be your last resort. I do not like to use it as the killed process leaves a lot of mess behind.

finds all forms instanciated into a symfony project, pruning svn files.

Get simple description on each file from /bin dir, in list form, usefull for newbies.

this will find text in the directory you specify and give you line where it appears.

/proc/cpuinfo contains information about the CPU.

Search for "processor" in the /proc/cpuinfo file

wc -l, counts the number of lines.

grep -sq "" filename && command

grep can be used in combination with && to run a command if a file exists.

The trick here is to use the brackets [ ] around any one of the characters of the grep string. This uses the fact that [?] is a character class of one letter and will be removed when parsed by the shell. This is useful when you want to parse the output of grep or use the return value in an if-statement without having its own process causing it to erroneously return TRUE.

Filter comments and empty lines in files. I find this very useful when trying to find what values are actually set in a very long example config file.

I often set an alias for it, like :

alias nocomment='grep -v "^\($\|#\)"'

only works for freeBSD where ports are installed in /usr/ports

credit to http://wiki.freebsd.org/PortsTasks

changes the PS1 to something better than default.

[username.hostname.last-2-digits-of-ip] (current directory)

Very useful set of commands to know when your file system was created.