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20 Unix Command Line Tricks – Part I
================================================================================
Let us start new year with **these Unix command line tricks** to increase productivity at the Terminal. I have found them over the years and I'm now going to share with you.
![](http://s0.cyberciti.org/uploads/cms/2015/01/unix-command-line-tricks.001.jpg)
### Deleting a HUGE file ###
I had a huge log file 200GB I need to delete on a production web server. My rm and ls command was crashed and I was afraid that the system to a crawl with huge disk I/O load. To remove a HUGE file, enter:
> /path/to/file.log
# or use the following syntax
: > /path/to/file.log
# finally delete it
rm /path/to/file.log
### Want to cache console output? ###
Try the script command line utility to create a typescript of everything printed on your terminal.
script my.terminal.sessio
Type commands:
ls
date
sudo service foo stop
To exit (to end script session) type *exit* or *logout* or press *control-D*
exit
To view type:
more my.terminal.session
less my.terminal.session
cat my.terminal.session
### Restoring deleted /tmp folder ###
As my journey continues with [Linux and Unix shell, I made a few mistakes][1]. I accidentally deleted /tmp folder. To restore it all you have to do is:
mkdir /tmp
chmod 1777 /tmp
chown root:root /tmp
ls -ld /tmp
### Locking a directory ###
For privacy of my data I wanted to lock down /downloads on my file server. So I ran:
chmod 0000 /downloads
The root user can still has access and ls and cd commands will not work. To go back:
chmod 0755 /downloads
### Password protecting file in vim text editor ###
Afraid that root user or someone may snoop into your personal text files? Try password protection to a file in vim, type:
vim +X filename
Or, before quitting in vim use :X vim command to encrypt your file and vim will prompt for a password.
### Clear gibberish all over the screen ###
Just type:
reset
### Becoming human ###
Pass the *-h* or *-H* (and other options) command line option to GNU or BSD utilities to get output of command commands like ls, df, du, in human-understandable formats:
ls -lh
# print sizes in human readable format (e.g., 1K 234M 2G)
df -h
df -k
# show output in bytes, KB, MB, or GB
free -b
free -k
free -m
free -g
# print sizes in human readable format (e.g., 1K 234M 2G)
du -h
# get file system perms in human readable format
stat -c %A /boot
# compare human readable numbers
sort -h -a file
# display the CPU information in human readable format on a Linux
lscpu
lscpu -e
lscpu -e=cpu,node
# Show the size of each file but in a more human readable way
tree -h
tree -h /boot
### Show information about known users in the Linux based system ###
Just type:
## linux version ##
lslogins
## BSD version ##
logins
Sample outputs:
UID USER PWD-LOCK PWD-DENY LAST-LOGIN GECOS
0 root 0 0 22:37:59 root
1 bin 0 1 bin
2 daemon 0 1 daemon
3 adm 0 1 adm
4 lp 0 1 lp
5 sync 0 1 sync
6 shutdown 0 1 2014-Dec17 shutdown
7 halt 0 1 halt
8 mail 0 1 mail
10 uucp 0 1 uucp
11 operator 0 1 operator
12 games 0 1 games
13 gopher 0 1 gopher
14 ftp 0 1 FTP User
27 mysql 0 1 MySQL Server
38 ntp 0 1
48 apache 0 1 Apache
68 haldaemon 0 1 HAL daemon
69 vcsa 0 1 virtual console memory owner
72 tcpdump 0 1
74 sshd 0 1 Privilege-separated SSH
81 dbus 0 1 System message bus
89 postfix 0 1
99 nobody 0 1 Nobody
173 abrt 0 1
497 vnstat 0 1 vnStat user
498 nginx 0 1 nginx user
499 saslauth 0 1 "Saslauthd user"
### How do I fix mess created by accidentally untarred files in the current dir? ###
So I accidentally untar a tarball in /var/www/html/ directory instead of /home/projects/www/current. It created mess in /var/www/html/. The easiest way to fix this mess:
cd /var/www/html/
/bin/rm -f "$(tar ztf /path/to/file.tar.gz)"
### Confused on a top command output? ###
Seriously, you need to try out htop instead of top:
sudo htop
### Want to run the same command again? ###
Just type !!. For example:
/myhome/dir/script/name arg1 arg2
# To run the same command again
!!
## To run the last command again as root user
sudo !!
The !! repeats the most recent command. To run the most recent command beginning with "foo":
!foo
# Run the most recent command beginning with "service" as root
sudo !service
The !$ use to run command with the last argument of the most recent command:
# Edit nginx.conf
sudo vi /etc/nginx/nginx.conf
# Test nginx.conf for errors
/sbin/nginx -t -c /etc/nginx/nginx.conf
# After testing a file with "/sbin/nginx -t -c /etc/nginx/nginx.conf", you
# can edit file again with vi
sudo vi !$
### ###Get a reminder you when you have to leave
If you need a reminder to leave your terminal, type the following command:
leave +hhmm
Where,
- **hhmm** - The time of day is in the form hhmm where hh is a time in hours (on a 12 or 24 hour clock), and mm are minutes. All times are converted to a 12 hour clock, and assumed to be in the next 12 hours.
### Home sweet home ###
Want to go the directory you were just in? Run:
cd -
Need to quickly return to your home directory? Enter:
cd
The variable *CDPATH* defines the search path for the directory containing directories:
export CDPATH=/var/www:/nas10
Now, instead of typing cd */var/www/html/* I can simply type the following to cd into /var/www/html path:
cd html
### Editing a file being viewed with less pager ###
To edit a file being viewed with less pager, press v. You will have the file for edit under $EDITOR:
less *.c
less foo.html
## Press v to edit file ##
## Quit from editor and you would return to the less pager again ##
### List all files or directories on your system ###
To see all of the directories on your system, run:
find / -type d | less
# List all directories in your $HOME
find $HOME -type d -ls | less
To see all of the files, run:
find / -type f | less
# List all files in your $HOME
find $HOME -type f -ls | less
### Build directory trees in a single command ###
You can create directory trees one at a time using mkdir command by passing the -p option:
mkdir -p /jail/{dev,bin,sbin,etc,usr,lib,lib64}
ls -l /jail/
### Copy file into multiple directories ###
Instead of running:
cp /path/to/file /usr/dir1
cp /path/to/file /var/dir2
cp /path/to/file /nas/dir3
Run the following command to copy file into multiple dirs:
echo /usr/dir1 /var/dir2 /nas/dir3 | xargs -n 1 cp -v /path/to/file
[Creating a shell function][2] is left as an exercise for the reader
### Quickly find differences between two directories ###
The diff command compare files line by line. It can also compare two directories:
ls -l /tmp/r
ls -l /tmp/s
# Compare two folders using diff ##
diff /tmp/r/ /tmp/s/
[![Fig. : Finding differences between folders](http://s0.cyberciti.org/uploads/cms/2015/01/differences-between-folders.jpg)][3]
Fig. : Finding differences between folders
### Text formatting ###
You can reformat each paragraph with fmt command. In this example, I'm going to reformat file by wrapping overlong lines and filling short lines:
fmt file.txt
You can also split long lines, but do not refill i.e. wrap overlong lines, but do not fill short lines:
fmt -s file.txt
### See the output and write it to a file ###
Use the tee command as follows to see the output on screen and also write to a log file named my.log:
mycoolapp arg1 arg2 input.file | tee my.log
The tee command ensures that you will see mycoolapp output on on the screen and to a file same time.
--------------------------------------------------------------------------------
via: http://www.cyberciti.biz/open-source/command-line-hacks/20-unix-command-line-tricks-part-i/
作者：[nixCraft][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://www.cyberciti.biz/tips/about-us
[1]:http://www.cyberciti.biz/tips/my-10-unix-command-line-mistakes.html
[2]:http://bash.cyberciti.biz/guide/Writing_your_first_shell_function
[3]:http://www.cyberciti.biz/open-source/command-line-hacks/20-unix-command-line-tricks-part-i/attachment/differences-between-folders/

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sources/tech/20150115 How To Extract a Tar Files To a Different Directory on a Linux or Unix-like Systems.md Normal file
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How To Extract a Tar Files To a Different Directory on a Linux/Unix-like Systems
================================================================================
I want to extract tar file to specific directory called /tmp/data. How can I extract a tar archive to a different directory using tar command on a Linux or Unix-like systems?
You do not need to change the directory using cd command and extract files. Untarring a file can be done using the following syntax:
### Syntax ###
Typical Unix tar syntax:
tar -xf file.name.tar -C /path/to/directory
GNU/tar syntax:
tar xf file.tar -C /path/to/directory
tar xf file.tar --directory /path/to/directory
### Example: Extract files to another directory ###
In this example, I'm extracting $HOME/etc.backup.tar file to a directory called /tmp/data. First, you have to create the directory manually, enter:
mkdir /tmp/data
To extract a tar archive $HOME/etc.backup.tar into a /tmp/data, enter:
tar -xf $HOME/etc.backup.tar -C /tmp/data
To see a progress pass the -v option:
tar -xvf $HOME/etc.backup.tar -C /tmp/data
Sample outputs:
![Gif 01: tar Command Extract Archive To Different Directory Command](http://s0.cyberciti.org/uploads/faq/2015/01/tar-extract-archive-to-dir.gif)
Gif 01: tar Command Extract Archive To Different Directory Command
You can extract specific files too use:
tar -xvf $HOME/etc.backup.tar file1 file2 file3 dir1 -C /tmp/data
To extract a foo.tar.gz (.tgz extension file) tarball to /tmp/bar, enter:
mkdir /tmp/bar
tar -zxvf foo.tar.gz -C /tmp/bar
To extract a foo.tar.bz2 (.tbz, .tbz2 & .tb2 extension file) tarball to /tmp/bar, enter:
mkdir /tmp/bar
tar -jxvf foo.tar.bz2 -C /tmp/bar
--------------------------------------------------------------------------------
via: http://www.cyberciti.biz/faq/howto-extract-tar-file-to-specific-directory-on-unixlinux/
作者：[nixCraft][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
[a]:http://www.cyberciti.biz/tips/about-us