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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 62
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 73
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 10:26:48 250
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 85
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 17:12:33 294

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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clear screen, keep prompt at eye-level (faster than clear(1), tput cl, etc.)

this leaves the cursor at the bottom of the terminal screen, where your eyes are. ctrl-l moves it to the top, forcing you to look up.

cd to (or operate on) a file across parallel directories

This is useful for quickly jumping around branches in a file system, or operating on a parellel file. This is tested in bash. cd to (substitute in PWD, a for b) where PWD is the bash environmental variable for the "working directory"

Copy a file to a new directory created on the fly

You need to cp, mv, scp, ..., some files around from one place to another, and after having laboriously typed out the source path, you remember that the destination directory doesn't yet exist, and so the command will fail. So rather than killing the command line and starting over, just interpolate the results of creating the directory and echo its name. You could DRY this with a for; do; done, but that may be more trouble than it's worth.

Install pip with Proxy

Installs pip packages defining a proxy

Check if a domain is available for purchase

A quick alias to check if a domain is already registered or if it's available for purchase.

port scan using parallel

It takes over 5 seconds to scan a single port on a single host using nmap $ time (nmap -p 80 192.168.1.1 &> /dev/null) real 0m5.109s user 0m0.102s sys 0m0.004s It took netcat about 2.5 minutes to scan port 80 on the class C $ time (for NUM in {1..255} ; do nc -w 1 -z -v 192.168.1.${NUM} 80 ; done &> /dev/null) real 2m28.651s user 0m0.136s sys 0m0.341s Using parallel, I am able to scan port 80 on the entire class C in under 2 seconds $ time (seq 1 255 | parallel -j255 'nc -w 1 -z -v 192.168.1.{} 80' &> /dev/null) real 0m1.957s user 0m0.457s sys 0m0.994s

Check your unread Gmail from the command line

Checks the Gmail ATOM feed for your account, parses it and outputs a list of unread messages. For some reason sed gets stuck on OS X, so here's a Perl version for the Mac: $ curl -u username:password --silent "https://mail.google.com/mail/feed/atom" | tr -d '\n' | awk -F '' '{for (i=2; i

Go to parent directory of filename edited in last command

Uses the last argument of the last executed command, and gets the directory name from it. Use $!:t for the filename alone, without the dirname.

set your ssd disk as a non-rotating medium

if you still get a permissions error using sudo, then nano the file: sudo nano -w /sys/block/sdb/queue/rotational and change 1 to 0 this thread: http://www.ocztechnologyforum.com/forum/showpost.php?p=369836&postcount=15 says that this will "help the block layer to optimize a few decisions"

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