Commands using grep

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.

Great for finding which jar some pesky class is hiding in!

Backups all MySQL databases to individual files. Can be put into a script that grabs current date so you have per day backups.

This gets you your default route programatically, useful for scripts

This is the simple revision number on stdout, that can be fed to any useful/fun script of yours. Setting LC_ALL is useful if you use another locale, in which case "Revision" is translated and cannot be found. I use this with doxygen to insert my source files revisions into the doc. An example in Doxyfile:

FILE_VERSION_FILTER = "function svn_filter { LC_ALL=C svn info $1 | grep Revision | awk '{print $2}'; }; svn_filter"

Share your ideas about what to do with the revision number !

This is just one method of checking to see if an IP is blocked via IP tables or CSF. Simple and to the point. Replace xx.xx.xx.xx with the IP you wish to check.