50个最常用的UNIX-Linux命令

1. 打包命令tar

压缩：$ tar cvf archive_name.tar dirname/

解压：$ tar xvf archive_name.tar

查看压缩包内容：$ tar tvf archive_name.tar

2. 匹配查找命令grep


在文件中搜索某字符串：$ grep -i "the" demo_file


打印匹配行和其后面的三行：$ grep -A 3 -i "example" demo_text


当前目录级联搜索字符串：$ grep -r "ramesh" *



3.查询命令 find



根据文件名查询：# find -iname "MyCProgram.c"

查到文件后执行命令：$ find -iname "MyCProgram.c" -exec md5sum {} \;

查找主目录空文件：# find ~ -empty



4. ssh command examples


Login to remote host


ssh -l jsmith remotehost.example.com


Debug ssh client


ssh -v -l jsmith remotehost.example.com


Display ssh client version


$ ssh -V
OpenSSH_3.9p1, OpenSSL 0.9.7a Feb 19 2003


More ssh examples: 5 Basic Linux SSH Client Commands
5. sed command examples


When you copy a DOS file to Unix, you could find \r\n in the end of each line. This example converts the DOS file format to Unix file format using sed command.


$sed 's/.$//' filename


Print file content in reverse order


$ sed -n '1!G;h;$p' thegeekstuff.txt


Add line number for all non-empty-lines in a file


$ sed '/./=' thegeekstuff.txt | sed 'N; s/\n/ /'


More sed examples: Advanced Sed Substitution Examples
6. awk command examples


Remove duplicate lines using awk


$ awk '!($0 in array) { array[$0]; print }' temp


Print all lines from /etc/passwd that has the same uid and gid


$awk -F ':' '$3==$4' passwd.txt


Print only specific field from a file.


$ awk '{print $2,$5;}' employee.txt


More awk examples: 8 Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR
7. vim command examples


Go to the 143rd line of file


$ vim +143 filename.txt


Go to the first match of the specified


$ vim +/search-term filename.txt


Open the file in read only mode.


$ vim -R /etc/passwd


More vim examples: How To Record and Play in Vim Editor
8. diff command examples


Ignore white space while comparing.


# diff -w name_list.txt name_list_new.txt


2c2,3
< John Doe --- > John M Doe
> Jason Bourne


More diff examples: Top 4 File Difference Tools on UNIX / Linux – Diff, Colordiff, Wdiff, Vimdiff
9. sort command examples


Sort a file in ascending order


$ sort names.txt


Sort a file in descending order


$ sort -r names.txt


Sort passwd file by 3rd field.


$ sort -t: -k 3n /etc/passwd | more


10. export command examples


To view oracle related environment variables.


$ export | grep ORACLE
declare -x ORACLE_BASE="/u01/app/oracle"
declare -x ORACLE_HOME="/u01/app/oracle/product/10.2.0"
declare -x ORACLE_SID="med"
declare -x ORACLE_TERM="xterm"


To export an environment variable:


$ export ORACLE_HOME=/u01/app/oracle/product/10.2.0


11. xargs command examples


Copy all images to external hard-drive


# ls *.jpg | xargs -n1 -i cp {} /external-hard-drive/directory


Search all jpg images in the system and archive it.


# find / -name *.jpg -type f -print | xargs tar -cvzf images.tar.gz


Download all the URLs mentioned in the url-list.txt file


# cat url-list.txt | xargs wget –c


12. ls command examples


Display filesize in human readable format (e.g. KB, MB etc.,)


$ ls -lh
-rw-r----- 1 ramesh team-dev 8.9M Jun 12 15:27 arch-linux.txt.gz


Order Files Based on Last Modified Time (In Reverse Order) Using ls -ltr


$ ls -ltr


Visual Classification of Files With Special Characters Using ls -F


$ ls -F


More ls examples: Unix LS Command: 15 Practical Examples
13. pwd command


pwd is Print working directory. What else can be said about the good old pwd who has been printing the current directory name for ages.
14. cd command examples


Use “cd -” to toggle between the last two directories


Use “shopt -s cdspell” to automatically correct mistyped directory names on cd


More cd examples: 6 Awesome Linux cd command Hacks
15. gzip command examples


To create a *.gz compressed file:


$ gzip test.txt


To uncompress a *.gz file:


$ gzip -d test.txt.gz


Display compression ratio of the compressed file using gzip -l


$ gzip -l *.gz
         compressed        uncompressed  ratio uncompressed_name
              23709               97975  75.8% asp-patch-rpms.txt


16. bzip2 command examples


To create a *.bz2 compressed file:


$ bzip2 test.txt


To uncompress a *.bz2 file:


bzip2 -d test.txt.bz2


More bzip2 examples: BZ is Eazy! bzip2, bzgrep, bzcmp, bzdiff, bzcat, bzless, bzmore examples
17. unzip command examples


To extract a *.zip compressed file:


$ unzip test.zip


View the contents of *.zip file (Without unzipping it):


$ unzip -l jasper.zip
Archive:  jasper.zip
  Length     Date   Time    Name
 --------    ----   ----    ----
    40995  11-30-98 23:50   META-INF/MANIFEST.MF
    32169  08-25-98 21:07   classes_
    15964  08-25-98 21:07   classes_names
    10542  08-25-98 21:07   classes_ncomp


18. shutdown command examples


Shutdown the system and turn the power off immediately.


# shutdown -h now


Shutdown the system after 10 minutes.


# shutdown -h +10


Reboot the system using shutdown command.


# shutdown -r now


Force the filesystem check during reboot.


# shutdown -Fr now


19. ftp command examples


Both ftp and secure ftp (sftp) has similar commands. To connect to a remote server and download multiple files, do the following.


$ ftp IP/hostname
ftp> mget *.html


To view the file names located on the remote server before downloading, mls ftp command as shown below.


ftp> mls *.html -
/ftptest/features.html
/ftptest/index.html
/ftptest/othertools.html
/ftptest/samplereport.html
/ftptest/usage.html


More ftp examples: FTP and SFTP Beginners Guide with 10 Examples
20. crontab command examples


View crontab entry for a specific user


# crontab -u john -l


Schedule a cron job every 10 minutes.


*/10 * * * * /home/ramesh/check-disk-space


More crontab examples: Linux Crontab: 15 Awesome Cron Job Examples
21. service command examples


Service command is used to run the system V init scripts. i.e Instead of calling the scripts located in the /etc/init.d/ directory with their full path, you can use the service command.


Check the status of a service:


# service ssh status


Check the steatus of all the services.


service --status-all


Restart a service.


# service ssh restart


22. ps command examples


ps command is used to display information about the processes that are running in the system.


While there are lot of arguments that could be passed to a ps command, following are some of the common ones.


To view current running processes.


$ ps -ef | more


To view current running processes in a tree structure. H option stands for process hierarchy.


$ ps -efH | more


23. free command examples


This command is used to display the free, used, swap memory available in the system.


Typical free command output. The output is displayed in bytes.


$ free
             total       used       free     shared    buffers     cached
Mem:       3566408    1580220    1986188          0     203988     902960
-/+ buffers/cache:     473272    3093136
Swap:      4000176          0    4000176


If you want to quickly check how many GB of RAM your system has use the -g option. -b option displays in bytes, -k in kilo bytes, -m in mega bytes.


$ free -g
             total       used       free     shared    buffers     cached
Mem:             3          1          1          0          0          0
-/+ buffers/cache:          0          2
Swap:            3          0          3


If you want to see a total memory ( including the swap), use the -t switch, which will display a total line as shown below.


ramesh@ramesh-laptop:~$ free -t
             total       used       free     shared    buffers     cached
Mem:       3566408    1592148    1974260          0     204260     912556
-/+ buffers/cache:     475332    3091076
Swap:      4000176          0    4000176
Total:     7566584    1592148    5974436


24. top command examples


top command displays the top processes in the system ( by default sorted by cpu usage ). To sort top output by any column, Press O (upper-case O) , which will display all the possible columns that you can sort by as shown below.


Current Sort Field:  P  for window 1:Def
Select sort field via field letter, type any other key to return


  a: PID        = Process Id              v: nDRT       = Dirty Pages count
  d: UID        = User Id                 y: WCHAN      = Sleeping in Function
  e: USER       = User Name               z: Flags      = Task Flags
  ........


To displays only the processes that belong to a particular user use -u option. The following will show only the top processes that belongs to oracle user.


$ top -u oracle


More top examples: Can You Top This? 15 Practical Linux Top Command Examples
25. df command examples


Displays the file system disk space usage. By default df -k displays output in bytes.


$ df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1             29530400   3233104  24797232  12% /
/dev/sda2            120367992  50171596  64082060  44% /home


df -h displays output in human readable form. i.e size will be displayed in GB’s.


ramesh@ramesh-laptop:~$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              29G  3.1G   24G  12% /
/dev/sda2             115G   48G   62G  44% /home


Use -T option to display what type of file system.


ramesh@ramesh-laptop:~$ df -T
Filesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1     ext4    29530400   3233120  24797216  12% /
/dev/sda2     ext4   120367992  50171596  64082060  44% /home


26. kill command examples


Use kill command to terminate a process. First get the process id using ps -ef command, then use kill -9 to kill the running Linux process as shown below. You can also use killall, pkill, xkill to terminate a unix process.


$ ps -ef | grep vim
ramesh    7243  7222  9 22:43 pts/2    00:00:00 vim


$ kill -9 7243


More kill examples: 4 Ways to Kill a Process – kill, killall, pkill, xkill
27. rm command examples


Get confirmation before removing the file.


$ rm -i filename.txt


It is very useful while giving shell metacharacters in the file name argument.


Print the filename and get confirmation before removing the file.


$ rm -i file*


Following example recursively removes all files and directories under the example directory. This also removes the example directory itself.


$ rm -r example


28. cp command examples


Copy file1 to file2 preserving the mode, ownership and timestamp.


$ cp -p file1 file2


Copy file1 to file2. if file2 exists prompt for confirmation before overwritting it.


$ cp -i file1 file2


29. mv command examples


Rename file1 to file2. if file2 exists prompt for confirmation before overwritting it.


$ mv -i file1 file2


Note: mv -f is just the opposite, which will overwrite file2 without prompting.


mv -v will print what is happening during file rename, which is useful while specifying shell metacharacters in the file name argument.


$ mv -v file1 file2


30. cat command examples


You can view multiple files at the same time. Following example prints the content of file1 followed by file2 to stdout.


$ cat file1 file2


While displaying the file, following cat -n command will prepend the line number to each line of the output.


$ cat -n /etc/logrotate.conf
    1 /var/log/btmp {
    2    missingok
    3    monthly
    4    create 0660 root utmp
    5    rotate 1
    6 }


31. mount command examples


To mount a file system, you should first create a directory and mount it as shown below.


# mkdir /u01


# mount /dev/sdb1 /u01


You can also add this to the fstab for automatic mounting. i.e Anytime system is restarted, the filesystem will be mounted.


/dev/sdb1 /u01 ext2 defaults 0 2


32. chmod command examples


chmod command is used to change the permissions for a file or directory.


Give full access to user and group (i.e read, write and execute ) on a specific file.


$ chmod ug+rwx file.txt


Revoke all access for the group (i.e read, write and execute ) on a specific file.


$ chmod g-rwx file.txt


Apply the file permissions recursively to all the files in the sub-directories.


$ chmod -R ug+rwx file.txt


More chmod examples: 7 Chmod Command Examples for Beginners
33. chown command examples


chown command is used to change the owner and group of a file. \


To change owner to oracle and group to db on a file. i.e Change both owner and group at the same time.


$ chown oracle:dba dbora.sh


Use -R to change the ownership recursively.


$ chown -R oracle:dba /home/oracle


34. passwd command examples


Change your password from command line using passwd. This will prompt for the old password followed by the new password.


$ passwd


Super user can use passwd command to reset others password. This will not prompt for current password of the user.


# passwd USERNAME


Remove password for a specific user. Root user can disable password for a specific user. Once the password is disabled, the user can login without entering the password.


# passwd -d USERNAME


35. mkdir command examples


Following example creates a directory called temp under your home directory.


$ mkdir ~/temp


Create nested directories using one mkdir command. If any of these directories exist already, it will not display any error. If any of these directories doesn’t exist, it will create them.


$ mkdir -p dir1/dir2/dir3/dir4/


36. ifconfig command examples


Use ifconfig command to view or configure a network interface on the Linux system.


View all the interfaces along with status.


$ ifconfig -a


Start or stop a specific interface using up and down command as shown below.


$ ifconfig eth0 up


$ ifconfig eth0 down


More ifconfig examples: Ifconfig: 7 Examples To Configure Network Interface
37. uname command examples


Uname command displays important information about the system such as — Kernel name, Host name, Kernel release number,
Processor type, etc.,


Sample uname output from a Ubuntu laptop is shown below.


$ uname -a
Linux john-laptop 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19 01:12:52 UTC 2010 i686 GNU/Linux


38. whereis command examples


When you want to find out where a specific Unix command exists (for example, where does ls command exists?), you can execute the following command.


$ whereis ls
ls: /bin/ls /usr/share/man/man1/ls.1.gz /usr/share/man/man1p/ls.1p.gz


When you want to search an executable from a path other than the whereis default path, you can use -B option and give path as argument to it. This searches for the executable lsmk in the /tmp directory, and displays it, if it is available.


$ whereis -u -B /tmp -f lsmk
lsmk: /tmp/lsmk


39. whatis command examples


Whatis command displays a single line description about a command.


$ whatis ls
ls (1)  - list directory contents


$ whatis ifconfig
ifconfig (8)         - configure a network interface


40. locate command examples


Using locate command you can quickly search for the location of a specific file (or group of files). Locate command uses the database created by updatedb.


The example below shows all files in the system that contains the word crontab in it.


$ locate crontab
/etc/anacrontab
/etc/crontab
/usr/bin/crontab
/usr/share/doc/cron/examples/crontab2english.pl.gz
/usr/share/man/man1/crontab.1.gz
/usr/share/man/man5/anacrontab.5.gz
/usr/share/man/man5/crontab.5.gz
/usr/share/vim/vim72/syntax/crontab.vim


41. man command examples


Display the man page of a specific command.


$ man crontab


When a man page for a command is located under more than one section, you can view the man page for that command from a specific section as shown below.


$ man SECTION-NUMBER commandname


Following 8 sections are available in the man page.


    General commands
    System calls
    C library functions
    Special files (usually devices, those found in /dev) and drivers
    File formats and conventions
    Games and screensavers
    Miscellaneous
    System administration commands and daemons


For example, when you do whatis crontab, you’ll notice that crontab has two man pages (section 1 and section 5). To view section 5 of crontab man page, do the following.


$ whatis crontab
crontab (1)          - maintain crontab files for individual users (V3)
crontab (5)          - tables for driving cron


$ man 5 crontab


42. tail command examples


Print the last 10 lines of a file by default.


$ tail filename.txt


Print N number of lines from the file named filename.txt


$ tail -n N filename.txt


View the content of the file in real time using tail -f. This is useful to view the log files, that keeps growing. The command can be terminated using CTRL-C.


$ tail -f log-file


More tail examples: 3 Methods To View tail -f output of Multiple Log Files in One Terminal
43. less command examples


less is very efficient while viewing huge log files, as it doesn’t need to load the full file while opening.


$ less huge-log-file.log


One you open a file using less command, following two keys are very helpful.


CTRL+F – forward one window
CTRL+B – backward one window


More less examples: Unix Less Command: 10 Tips for Effective Navigation
44. su command examples


Switch to a different user account using su command. Super user can switch to any other user without entering their password.


$ su - USERNAME


Execute a single command from a different account name. In the following example, john can execute the ls command as raj username. Once the command is executed, it will come back to john’s account.


[john@dev-server]$ su - raj -c 'ls'


[john@dev-server]$


Login to a specified user account, and execute the specified shell instead of the default shell.


$ su -s 'SHELLNAME' USERNAME


45. mysql command examples


mysql is probably the most widely used open source database on Linux. Even if you don’t run a mysql database on your server, you might end-up using the mysql command ( client ) to connect to a mysql database running on the remote server.


To connect to a remote mysql database. This will prompt for a password.


$ mysql -u root -p -h 192.168.1.2


To connect to a local mysql database.


$ mysql -u root -p


If you want to specify the mysql root password in the command line itself, enter it immediately after -p (without any space).
46. yum command examples


To install apache using yum.


$ yum install httpd


To upgrade apache using yum.


$ yum update httpd


To uninstall/remove apache using yum.


$ yum remove httpd


47. rpm command examples


To install apache using rpm.


# rpm -ivh httpd-2.2.3-22.0.1.el5.i386.rpm


To upgrade apache using rpm.


# rpm -uvh httpd-2.2.3-22.0.1.el5.i386.rpm


To uninstall/remove apache using rpm.


# rpm -ev httpd


More rpm examples: RPM Command: 15 Examples to Install, Uninstall, Upgrade, Query RPM Packages
48. ping command examples


Ping a remote host by sending only 5 packets.


$ ping -c 5 gmail.com


More ping examples: Ping Tutorial: 15 Effective Ping Command Examples
49. date command examples


Set the system date:


# date -s "01/31/2010 23:59:53"


Once you’ve changed the system date, you should syncronize the hardware clock with the system date as shown below.


# hwclock –systohc


# hwclock --systohc –utc


50. wget command examples


The quick and effective method to download software, music, video from internet is using wget command.


$ wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.2.1.tar.gz


Download and store it with a different name.


$ wget -O taglist.zip http://www.vim.org/scripts/download_script.php?src_id