09.12.2021
Dieser Artikel enthält viele praktische Beispiele für die am häufigsten unter Linux / UNIX verwendeten Befehle.
0x01. tar Befehls Beispiele
Erstellen eines Tar-Archives
tar cvf archive_name.tar dirname/
Dateien aus einem bestehenden Tar-Archiv extrahieren
tar xvf archive_name.tar
Ein bestehendes Tar-Archiv ansehen
tar tvf archive_name.tar
0x02. grep Befehls Beispiele
Suche nach einem vorgegebenen String in einer Datei (case in-sensitive search).
grep -i "the" demo_file
Die gefundene Zeile + 3 Zeilen danach ausgeben
grep -A 3 -i "example" demo_text
Suche nach einem String in allen Dateien recursive
grep -r "ramesh" *
0x03. find Befehls Beispiele
Find files using file-name ( case in-sensitve find)
find -iname "MyCProgram.c"
Execute commands on files found by the find command
find -iname "MyCProgramcode.c" -exec md5sum {} ;
Find all empty files in home directory
find ~ -empty
0x04. ssh Befehls Beispiele
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 18 2021
0x05. sed Befehls Beispiele
When you copy a DOS file to Unix, you could find rn 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' lxuiotuff.txt
Add line number for all non-empty-lines in a file
sed '/./=' lxuiostuff.txt | sed 'N; s/n/ /'
0x06. awk Befehls Beispiele
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
0x07. vim Befehls Beispiele
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
0x08. diff Befehls Beispiele
Ignore white space while comparing.
diff -w name_list.txt name_list_new.txt
2c2,3
< John Doe --- > John M Doe
Jason Bourne
0x09. sort Befehls Beispiele
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
0x10. export Befehls Beispiele
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
0x11. xargs Befehls Beispiele
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
0x12. ls Befehls Beispiele
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
0x13. 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.
0x14. cd Befehls Beispiele
Use “cd -” to toggle between the last two directories
Use “shopt -s cdspell” to automatically correct mistyped directory names on cd
0x15. gzip Befehls Beispiele
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
0x16. bzip2 Befehls Beispiele
To create a *.bz2 compressed file:
bzip2 test.txt
To uncompress a *.bz2 file:
bzip2 -d test.txt.bz2
0x17. unzip Befehls Beispiele
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
0x18. shutdown Befehls Beispiele
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
0x19. ftp Befehls Beispiele
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
0x20. crontab Befehls Beispiele
View crontab entry for a specific user
crontab -u john -l
Schedule a cron job every 10 minutes.
*/10 * * * * /home/ramesh/check-disk-space
0x21. service Befehls Beispiele
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 status of all the services.
service --status-all
Restart a service.
service ssh restart
0x22. ps Befehls Beispiele
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
0x23. free Befehls Beispiele
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.
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
0x24. top Befehls Beispiele
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
0x25. df Befehls Beispiele
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.
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.
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
0x26. kill Befehls Beispiele
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
0x27. rm Befehls Beispiele
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
0x28. cp Befehls Beispiele
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
0x29. mv Befehls Beispiele
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
0x30. cat Befehls Beispiele
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 }
0x31. mount Befehls Beispiele
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
0x32. chmod Befehls Beispiele
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
0x33. chown Befehls Beispiele
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
0x34. passwd Befehls Beispiele
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
0x35. mkdir Befehls Beispiele
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/
0x36. ifconfig Befehls Beispiele
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
0x37. uname Befehls Beispiele
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
0x38. whereis Befehls Beispiele
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
0x39. whatis Befehls Beispiele
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
0x40. locate Befehls Beispiele
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
0x41. man Befehls Beispiele
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
0x42. tail Befehls Beispiele
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
0x43. less Befehls Beispiele
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
0x44. su Befehls Beispiele
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.
su - raj -c 'ls'
Login to a specified user account, and execute the specified shell instead of the default shell.
su -s 'SHELLNAME' USERNAME
0x45. mysql Befehls Beispiele
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).
0x46. yum Befehls Beispiele
#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
0x47. rpm Befehls Beispiele
#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
0x48. ping Befehls Beispiele
Ping a remote host by sending only 5 packets.
ping -c 5 gmail.com
0x49. date Befehls Beispiele
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
0x50. wget Befehls Beispiele
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=7701
“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.”
Can be said that pwd -P shows the real path if you cd into a link..
Example
cd /home/user
ln -s ./Public ./Pub
cd Pub
pwd /home/user/Pub
pwd -P /home/nnsense/Public
#!/bin/sh
cp file.txt temp.txt n=`cat file.txt | wc -l` while [ $n -ge 0 ]
do
tail -1 temp.txt >> result.txt sed -i ‘$ d’ temp.txt n=`expr $n – 1`
done
rm -f temp.txt cat result.txt
Here is a “safe” alternative to
sed ‘s/.$//’ filename
which will only remove rn at the end of lines (as “.” matches any character.):
perl -pe ‘s/rn$/n/g’ filename
Replaces all instances of rn with n
How about cpio? Particularly the
find ./ | cpio combo
ie:
find ./ -mount -depth -print | cpio -pdm /destination_dir