I needed a way to search all files in a web directory that contained a certain string, and replace that string with another string. In the example, I am searching for "askapache" and replacing that string with "htaccess". I wanted this to happen as a cron job, and it was important that this happened as fast as possible while at the same time not hogging the CPU since the machine is a server.

So this script uses the nice command to run the sh shell with the command, which makes the whole thing run with priority 19, meaning it won't hog CPU processing. And the -P5 option to the xargs command means it will run 5 separate grep and sed processes simultaneously, so this is much much faster than running a single grep or sed. You may want to do -P0 which is unlimited if you aren't worried about too many processes or if you don't have to deal with process killers in the bg.

Also, the -m1 command to grep means stop grepping this file for matches after the first match, which also saves time.

No need to loop when we have `xargs`. The sed command filters out the first line of `show databases` output, which is always "Database".

change the *.avi to whatever you want to match, you can remove it altogether if you want to check all files.

You're behind on your TV catch-up, but how far behind? This command tries to open mplayer against all files in the current dir. If it's a video file it will contain ID_LENGTH, which is summed and output in hours, minutes and seconds.

Someone better at awk could probably reduce this down a lot.

List all text files in the current directory.

This dup finder saves time by comparing size first, then md5sum, it doesn't delete anything, just lists them.

I sometimes (due to mismanagement!) end up with files in a git repo which have had their modes changed, but not their content. This one-liner lets me revert the mode changes, while leaving changed-content files be, so I can commit just the actual changes made.

yes 6 (tail from 6th line)

A little bit smaller, faster and should handle files with special characters in the name.

This helped me find a botnet that had made into my system. Of course, this is not a foolproof or guarantied way to find all of them or even most of them. But it helped me find it.

This is really fast :)

204753

real 0m0.191s

user 0m0.068s

sys 0m0.116s

Based on the MrMerry one, just add some visuals and sort directory and files

Make sure that find does not touch anything other than regular files, and handles non-standard characters in filenames while passing to xargs.

needs no GNU tools, as far as I see it

saves one command. Needs GNU grep though :-(

The grep switches eliminate the need for awk and sed. Modifying vim with -p will show all files in separate tabs, -o in separate vim windows. Just wish it didn't hose my terminal once I exit vim!!

This will drop you into vim to edit all files that contain your grep string.

xargs can be used in this manner to download multiple files at a time, and xargs will in this case run 10 processes at a time and initiate a new one when the number running falls below 10.

get diskusage of files (in this case logfiles in /var/log) modified during the last n days:

n -> last modified n*24 hours ago

Numeric arguments can be specified as

+n for greater than n,

-n for less than n,

n for exactly n.

=> so 7*24 hours (about 7 days) is -7

1. find file greater than 10 MB

2. direct it to xargs

3. xargs pass them as argument to ls

this command works with one gziped file per table, and restore 4 tables in parallel.