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Optimal way of deleting huge numbers of files

Using xargs is better than: find /path/to/dir -type f -exec rm \-f {} \; as the -exec switch uses a separate process for each remove. xargs splits the streamed files into more managable subsets so less processes are required.
This is sample output - yours may be different.
12

find /path/to/dir -type f -print0 | xargs -0 rm

root · 2009-01-26 11:30:47 64
Display PHP files that directly instantiate a given class

This greps all PHP files for a given classname and displays both the file and the usage. Show Sample Output
This is sample output - yours may be different.
```
tao/tests/filter/TestUrl.php:        $this->objFilter = new filter_Url();
tao/classes/local/view/Photos.php:        $objFilter  = new filter_Url();
```
1

find . -name "*.php" -exec grep \-H "new filter_" {} \;

root · 2009-01-26 10:43:09 77
Run the last command as root

Useful when you forget to use sudo for a command. "!!" grabs the last run command.
This is sample output - yours may be different.
1219

sudo !!

root · 2009-01-26 10:26:48 263
Creates a customized search command

Creates a command alias ('cr' in the above example) that searches the contents of files matching a set of file extensions (C & C++ source-code in the above example) recursively within the current directory. Search configured to be in colour, ignore-case, show line numbers and show 4 lines of context. Put in shell initialisation file of your choice. Trivially easy to use, e.g: cr sha1_init Show Sample Output
This is sample output - yours may be different.
```
./openssl/signatures.c-600-xmlSecOpenSSLDsaSha1EvpInit(EVP_MD_CTX *ctx)
./openssl/signatures.c-601-{
./openssl/signatures.c:602:    return SHA1_Init(ctx->md_data);
./openssl/signatures.c-603-}
./openssl/signatures.c-604-
--
./openssl/signatures.c-706-    NULL,
./openssl/signatures.c-707-#else /* XMLSEC_OPENSSL_096 */
./openssl/signatures.c:708:    SHA1_Init,
./openssl/signatures.c-709-    SHA1_Update,
./openssl/signatures.c-710-    SHA1_Final,
```
0

alias cr='find . 2>/dev/null -regex '\''.*\.$c\|cpp\|pc\|h\|hpp\|cc$$'\'' | xargs grep --color=always -ni -C2'

chrisdrew · 2009-01-26 08:54:25 56
Outputs a sorted list of disk usage to a text file

Recursively searches current directory and outputs sorted list of each directory's disk usage to a text file. Show Sample Output
This is sample output - yours may be different.
```
712     .
328     ./test
176     ./lib
144     ./doc
100     ./test/data
96      ./lib/rake
64      ./doc/release_notes
```
6

du | sort -gr > file_sizes

chrisdrew · 2009-01-26 01:12:54 62
Watch how fast the files in a drive are being deleted

This can be useful when a large remove operation is taking place.
This is sample output - yours may be different.
6

watch "df | grep /path/to/drive"

root · 2009-01-25 21:16:41 674
Execute a command at a given time

This is an alternative to cron which allows a one-off task to be scheduled for a certain time.
This is sample output - yours may be different.
266

echo "ls -l" | at midnight

root · 2009-01-25 21:07:42 86
Analyse an Apache access log for the most common IP addresses

This uses awk to grab the IP address from each request and then sorts and summarises the top 10.
This is sample output - yours may be different.
22

tail -10000 access_log | awk '{print $1}' | sort | uniq -c | sort -n | tail

root · 2009-01-25 21:01:52 47
Add SVN keywords property to all PHP and Javascript files
This is sample output - yours may be different.
3

find . $ -name "*.php" -o -name "*.js" $ -exec svn propset svn:keywords Id {} \;

root · 2009-01-24 00:54:35 63
Count files beneath current directory (including subfolders)
This is sample output - yours may be different.
18

find . -type f | wc -l

root · 2009-01-23 17:19:32 74

Display the top ten running processes - sorted by memory usage

ps returns all running processes which are then sorted by the 4th field in numerical order and the top 10 are sent to STDOUT. Show Sample Output

106

ps aux | sort -nk +4 | tail

root · 2009-01-23 17:12:33 295

Checks all MySQL tables

See http://dev.mysql.com/doc/refman/5.0/en/myisamchk.html for further details. You can also repair all tables by running: myisamchk -r *.MYI
This is sample output - yours may be different.
-2

myisamchk /path/to/mysql/files/*.MYI

root · 2009-01-22 10:20:00 133
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Prevent non-root users from logging in

Also with optional message: $ echo "no login for you" > /etc/nologin (This doesn't affect your current X session - you're already logged in!)

Find brute force attempts on SSHd

Searches the /var/log/secure log file for Failed and/or invalid user log in attempts.

list block devices

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

determine if a shared library is compiled as 32bit or 64bit

Determines the flavor of a shared library by looking at the addresses of its exposed functions and seeing if they are 16 bytes or 8 bytes long. The command is written so the library you are querying is passed to a variable up font -- it would be simple to convert this to a bash function or script using this format.

download specific files only from a website

Huh? Where did all my precious space go ?

Sort ls output of all files in current directory in ascending order Just the 20 biggest ones: $ ls -la | sort -k 5bn | tail -n 20 A variant for the current directory tree with subdirectories and pretty columns is: $ find . -type f -print0 | xargs -0 ls -la | sort -k 5bn | column -t And finding the subdirectories consuming the most space with displayed block size 1k: $ du -sk ./* | sort -k 1bn | column -t

play high-res video files on a slow processor

Certain codecs in high res don't play so well on my Dell Mini 9. Using this command, I can play just about anything and it keeps the sound in sync to boot!

Securely destroy data (including whole hard disks)

GNU shred is provided by the coreutils package on most Linux distribution (meaning, you probably have it installed already), and is capable of wiping a device to DoD standards. You can give shred any file to destroy, be it your shell history or a block device file (/dev/hdX, for IDE hard drive X, for example). Shred will overwrite the target 25 times by default, but 3 is enough to prevent most recovery, and 7 passes is enough for the US Department of Defense. Use the -n flag to specify the number of passes, and man shred for even more secure erasing fun. Note that shredding your shell history may not be terribly effective on devices with journaling filesystems, RAID copies or snapshot copies, but if you're wiping a single disk, none of that is a concern. Also, it takes quite a while :)

Get your current Public IP

Create backup copy of file, adding suffix of the date of the file modification (NOT today's date)

When I go to change a configuration file I always like to make a backup first. You can use "cp -p" to preserve the modification time, but it gets confusing to have file.prev, file.prev2, etc. So I like to add a YYMMDD suffix that shows when the file was last changed. "stat -c %Y" gives you the modification time in epoch seconds, then "date -d @" converts that to whatever format you specify in your "+format" string.

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