Linux Commands

Linux Commands that I rarely use and often forget.

Print Working Directory (pwd)

pwd = (Print Working Directory) Displays the current directory you're in.

Network Map (nmap)

nmap = (Network Map) Utility that displays open network ports.
Basic usage: nmap 192.168.0.1

String Filter (grep)

grep = Hard to explain, Filtering utility.
Basic usage: grep 'FilterString' filename
Usefull grep options:

-i 'FilterString'   =   case insensitive
-b #                =   Display # number of lines BEFORE a match
-a #                =   Display # number of lines AFTER a match
-v                  =   Invert Match or Exclusion
'FilterString1\|FilterString2\|FilterString3'  =  Multiple Filters

Remove Comments from files

grep -v '#' FileName1 > FileName2

Remove Whitespace from files

grep -v "^$" FileName1 > FileName2

Remove Comments and Whitespace

grep -v '#\|^$' FileName > FileName2

List File/Directory Size

du = List the size of a file or Directory
Basic usage: du -hs <file or dir>
Usefull du options:

-h                  = human readable
-s                  = summarize (Display only total for each arguement)

File Comptession (tar)

Basic usage

to create a tar archive:

tar -pcvzf filename.tgz directory1/ directory2/

to extract an archive

tar -xvzf filename.tgz -C destination_directory/

Usefull tar options:

-x                  = extract
-c                  = create
-v                  = verbose (displays whats being archived or extracted on screen)
-j                  = use BZip format (.tar.bz2)
-z                  = use GZip format (.tar.gz or .tgz)
-p                  = Preserve file permissions
-f                  = File
-M                  = Multi-Volume
-L                  = Tape Length (or --tape-length=) accepts values in Kb.  Size = value x 1024

Span Multiple Files Example This will create multiple files 100MB in size (100 x 1024 = 102400)

tar -c -M -L=102400 --file=filename.part1.tar largefile.to.split.iso

When the first part is complete you will be presented a prompt like this:

Prepare Volume #2 for 'filename.part1.tar' and hit return:

To tell Tar that we want to continue with a new file we enter this:

n filename.part2.tar

Now you will be presented this prompt:

Prepare Volume #2 for 'filename.part2.tar' and hit return:

Notice the filename was accepted filename.part2.tar'. Now just press return

To Extract spanned tar files do this:

tar -x -M --file=filename.part1.tar largefile.that.was.split.iso

You will be prompted with this:

Prepare volume #2 for filename.part1.tar and hit return: n filename.part2.tar

Prepare volume #2 for filename.part2.tar and hit return: Now Press Retuen. Thats it.

Symbolic Links (symlinks)

ln -s path/to/target linkname

or if the linkname is going to be the same as the source filename then

ln -s path/to/target

This would create a symlink named target that would point to path/to/target ( target -> path/to/target )
Note: This also works for directories.

Find

Find all conf files on your system

find / -iname "*.conf"

Find files who haven't been modified in 1 year

find / -type f -mtime +356 -print0

-mtime = modified time -print0 = needed to display files containing white space -type f = files (not directories)

Find old files who haven't been modified in the past 2 years and display their total disk usage

find / -type f -mtime 730 -print0 | du --files0-from=- -hc | tail -n1

Turn off Linux Case Sensitivity

shopt -u nocasematch

shopt -s nocasematch

More to come...