OpenCores
URL https://opencores.org/ocsvn/oms8051mini/oms8051mini/trunk

Subversion Repositories oms8051mini

[/] [oms8051mini/] [trunk/] [help/] [help.50.unix.txt] - Blame information for rev 33

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 17 dinesha
50 Most Frequently Used UNIX / Linux Commands (With Examples)
2
 
3
http://www.thegeekstuff.com/2010/11/50-linux-commands/
4
 
5
This article provides practical examples for 50 most frequently used commands in Linux / UNIX.
6
 
7
1.      tar command examples
8
     Create a new tar archive.
9
     > tar cvf archive_name.tar dirname/
10
     Extract from an existing tar archive.
11
     > tar xvf archive_name.tar
12
     View an existing tar archive.
13
     > tar tvf archive_name.tar
14
2. grep command examples
15
     Search for a given string in a file (case in-sensitive search).
16
     > grep -i "the" demo_file
17
     Print the matched line, along with the 3 lines after it.
18
     > grep -A 3 -i "example" demo_text
19
     Search for a given string in all files recursively
20
     > grep -r "ramesh" *
21
3. find command examples
22
     Find files using file-name ( case in-sensitve find)
23
     # find -iname "MyCProgram.c"
24
     Execute commands on files found by the find command
25
     $ find -iname "MyCProgram.c" -exec md5sum {} \;
26
     Find all empty files in home directory
27
     # find ~ -empty
28
4. ssh command examples
29
     Login to remote host
30
     ssh -l jsmith remotehost.example.com
31
     Debug ssh client
32
     ssh -v -l jsmith remotehost.example.com
33
     Display ssh client version
34
     > ssh -V
35
     OpenSSH_3.9p1, OpenSSL 0.9.7a Feb 19 2003
36
5. sed command examples
37
     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.
38
     > sed 's/.$//' filename
39
     Print file content in reverse order
40
     > sed -n '1!G;h;$p' thegeekstuff.txt
41
     Add line number for all non-empty-lines in a file
42
     > sed '/./=' thegeekstuff.txt | sed 'N; s/\n/ /'
43
6. awk command examples
44
     Remove duplicate lines using awk
45
     > awk '!($0 in array) { array[$0]; print }' temp
46
     Print all lines from /etc/passwd that has the same uid and gid
47
     > awk -F ':' '$3==$4' passwd.txt
48
     Print only specific field from a file.
49
     > awk '{print $2,$5;}' employee.txt
50
7. vim command examples
51
    Go to the 143rd line of file
52
    $ vim +143 filename.txt
53
    Go to the first match of the specified
54
    $ vim +/search-term filename.txt
55
    Open the file in read only mode.
56
    $ vim -R /etc/passwd
57
8. diff command examples
58
    Ignore white space while comparing.
59
    # diff -w name_list.txt name_list_new.txt
60
 
61
    2c2,3
62
    < John Doe --- > John M Doe
63
    > Jason Bourne
64
9. sort command examples
65
    Sort a file in ascending order
66
    $ sort names.txt
67
    Sort a file in descending order
68
    $ sort -r names.txt
69
    Sort passwd file by 3rd field.
70
    $ sort -t: -k 3n /etc/passwd | more
71
10. export command examples
72
    To view oracle related environment variables.
73
    $ export | grep ORACLE
74
    declare -x ORACLE_BASE="/u01/app/oracle"
75
    declare -x ORACLE_HOME="/u01/app/oracle/product/10.2.0"
76
    declare -x ORACLE_SID="med"
77
    declare -x ORACLE_TERM="xterm"
78
    To export an environment variable:
79
    $ export ORACLE_HOME=/u01/app/oracle/product/10.2.0
80
11. xargs command examples
81
    Copy all images to external hard-drive
82
    # ls *.jpg | xargs -n1 -i cp {} /external-hard-drive/directory
83
    Search all jpg images in the system and archive it.
84
    # find / -name *.jpg -type f -print | xargs tar -cvzf images.tar.gz
85
    Download all the URLs mentioned in the url-list.txt file
86
    # cat url-list.txt | xargs wget -c
87
12. ls command examples
88
    Display filesize in human readable format (e.g. KB, MB etc.,)
89
    $ ls -lh
90
    -rw-r----- 1 ramesh team-dev 8.9M Jun 12 15:27 arch-linux.txt.gz
91
    Order Files Based on Last Modified Time (In Reverse Order) Using ls -ltr
92
    $ ls -ltr
93
    Visual Classification of Files With Special Characters Using ls -F
94
    $ ls -F
95
13. pwd command
96
    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.
97
14. cd command examples
98
    Use "cd -" to toggle between the last two directories
99
15. gzip command examples
100
    To create a *.gz compressed file:
101
    $ gzip test.txt
102
    To uncompress a *.gz file:
103
    $ gzip -d test.txt.gz
104
    Display compression ratio of the compressed file using gzip -l
105
    $ gzip -l *.gz
106
             compressed        uncompressed  ratio uncompressed_name
107
                  23709               97975  75.8% asp-patch-rpms.txt
108
16. bzip2 command examples
109
    To create a *.bz2 compressed file:
110
    $ bzip2 test.txt
111
    To uncompress a *.bz2 file:
112
    bzip2 -d test.txt.bz2
113
17. unzip command examples
114
    To extract a *.zip compressed file:
115
    $ unzip test.zip
116
    View the contents of *.zip file (Without unzipping it):
117
    $ unzip -l jasper.zip
118
    Archive:  jasper.zip
119
      Length     Date   Time    Name
120
     --------    ----   ----    ----
121
        40995  11-30-98 23:50   META-INF/MANIFEST.MF
122
        32169  08-25-98 21:07   classes_
123
        15964  08-25-98 21:07   classes_names
124
        10542  08-25-98 21:07   classes_ncomp
125
18. shutdown command examples
126
    Shutdown the system and turn the power off immediately.
127
    # shutdown -h now
128
    Shutdown the system after 10 minutes.
129
    # shutdown -h +10
130
    Reboot the system using shutdown command.
131
    # shutdown -r now
132
    Force the filesystem check during reboot.
133
    # shutdown -Fr now
134
19. ftp command examples
135
    Both ftp and secure ftp (sftp) has similar commands. To connect to a remote server and download multiple files, do the following.
136
    $ ftp IP/hostname
137
    ftp> mget *.html
138
    To view the file names located on the remote server before downloading, mls ftp command as shown below.
139
    ftp> mls *.html -
140
    /ftptest/features.html
141
    /ftptest/index.html
142
    /ftptest/othertools.html
143
    /ftptest/samplereport.html
144
    /ftptest/usage.html
145
20. crontab command examples
146
    View crontab entry for a specific user
147
    # crontab -u john -l
148
    Schedule a cron job every 10 minutes.
149
    */10 * * * * /home/ramesh/check-disk-space
150
21. service command examples
151
    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.
152
    Check the status of a service:
153
    # service ssh status
154
    Check the status of all the services.
155
    service --status-all
156
    Restart a service.
157
    # service ssh restart
158
22. ps command examples
159
    ps command is used to display information about the processes that are running in the system.
160
    While there are lot of arguments that could be passed to a ps command, following are some of the common ones.
161
    To view current running processes.
162
    $ ps -ef | more
163
    To view current running processes in a tree structure. H option stands for process hierarchy.
164
    $ ps -efH | more
165
23. free command examples
166
    This command is used to display the free, used, swap memory available in the system.
167
    Typical free command output. The output is displayed in bytes.
168
    $ free
169
                 total       used       free     shared    buffers     cached
170
    Mem:       3566408    1580220    1986188          0     203988     902960
171
    -/+ buffers/cache:     473272    3093136
172
    Swap:      4000176          0    4000176
173
    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.
174
    $ free -g
175
                 total       used       free     shared    buffers     cached
176
    Mem:             3          1          1          0          0          0
177
    -/+ buffers/cache:          0          2
178
    Swap:            3          0          3
179
    If you want to see a total memory ( including the swap), use the -t switch, which will display a total line as shown below.
180
    ramesh@ramesh-laptop:~$ free -t
181
                 total       used       free     shared    buffers     cached
182
    Mem:       3566408    1592148    1974260          0     204260     912556
183
    -/+ buffers/cache:     475332    3091076
184
    Swap:      4000176          0    4000176
185
    Total:     7566584    1592148    5974436
186
24. top command examples
187
    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.
188
    Current Sort Field:  P  for window 1:Def
189
    Select sort field via field letter, type any other key to return
190
 
191
      a: PID        = Process Id              v: nDRT       = Dirty Pages count
192
      d: UID        = User Id                 y: WCHAN      = Sleeping in Function
193
      e: USER       = User Name               z: Flags      = Task Flags
194
      ........
195
    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.
196
    $ top -u oracle
197
25. df command examples
198
    Displays the file system disk space usage. By default df -k displays output in bytes.
199
    $ df -k
200
    Filesystem           1K-blocks      Used Available Use% Mounted on
201
    /dev/sda1             29530400   3233104  24797232  12% /
202
    /dev/sda2            120367992  50171596  64082060  44% /home
203
    df -h displays output in human readable form. i.e size will be displayed in GB's.
204
    ramesh@ramesh-laptop:~$ df -h
205
    Filesystem            Size  Used Avail Use% Mounted on
206
    /dev/sda1              29G  3.1G   24G  12% /
207
    /dev/sda2             115G   48G   62G  44% /home
208
    Use -T option to display what type of file system.
209
    ramesh@ramesh-laptop:~$ df -T
210
    Filesystem    Type   1K-blocks      Used Available Use% Mounted on
211
    /dev/sda1     ext4    29530400   3233120  24797216  12% /
212
    /dev/sda2     ext4   120367992  50171596  64082060  44% /home
213
26. kill command examples
214
    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.
215
    $ ps -ef | grep vim
216
    ramesh    7243  7222  9 22:43 pts/2    00:00:00 vim
217
 
218
    $ kill -9 7243
219
27. rm command examples
220
    Get confirmation before removing the file.
221
    $ rm -i filename.txt
222
    It is very useful while giving shell metacharacters in the file name argument.
223
    Print the filename and get confirmation before removing the file.
224
    $ rm -i file*
225
    Following example recursively removes all files and directories under the example directory. This also removes the example directory itself.
226
    $ rm -r example
227
28. cp command examples
228
    Copy file1 to file2 preserving the mode, ownership and timestamp.
229
    $ cp -p file1 file2
230
    Copy file1 to file2. if file2 exists prompt for confirmation before overwritting it.
231
    $ cp -i file1 file2
232
29. mv command examples
233
    Rename file1 to file2. if file2 exists prompt for confirmation before overwritting it.
234
    $ mv -i file1 file2
235
    Note: mv -f is just the opposite, which will overwrite file2 without prompting.
236
    mv -v will print what is happening during file rename, which is useful while specifying shell metacharacters in the file name argument.
237
    $ mv -v file1 file2
238
30. cat command examples
239
    You can view multiple files at the same time. Following example prints the content of file1 followed by file2 to stdout.
240
    $ cat file1 file2
241
    While displaying the file, following cat -n command will prepend the line number to each line of the output.
242
    $ cat -n /etc/logrotate.conf
243
        1       /var/log/btmp {
244
        2           missingok
245
        3           monthly
246
        4           create 0660 root utmp
247
        5           rotate 1
248
        6       }
249
31. mount command examples
250
    To mount a file system, you should first create a directory and mount it as shown below.
251
    # mkdir /u01
252
 
253
    # mount /dev/sdb1 /u01
254
    You can also add this to the fstab for automatic mounting. i.e Anytime system is restarted, the filesystem will be mounted.
255
    /dev/sdb1 /u01 ext2 defaults 0 2
256
32. chmod command examples
257
    chmod command is used to change the permissions for a file or directory.
258
    Give full access to user and group (i.e read, write and execute ) on a specific file.
259
    $ chmod ug+rwx file.txt
260
    Revoke all access for the group (i.e read, write and execute ) on a specific file.
261
    $ chmod g-rwx file.txt
262
    Apply the file permissions recursively to all the files in the sub-directories.
263
    $ chmod -R ug+rwx file.txt
264
33. chown command examples
265
    chown command is used to change the owner and group of a file. \
266
    To change owner to oracle and group to db on a file. i.e Change both owner and group at the same time.
267
    $ chown oracle:dba dbora.sh
268
    Use -R to change the ownership recursively.
269
    $ chown -R oracle:dba /home/oracle
270
34. passwd command examples
271
    Change your password from command line using passwd. This will prompt for the old password followed by the new password.
272
    $ passwd
273
    Super user can use passwd command to reset others password. This will not prompt for current password of the user.
274
    # passwd USERNAME
275
    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.
276
    # passwd -d USERNAME
277
35. mkdir command examples
278
   Following example creates a directory called temp under your home directory.
279
   $ mkdir ~/temp
280
   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.
281
   $ mkdir -p dir1/dir2/dir3/dir4/
282
36. ifconfig command examples
283
   Use ifconfig command to view or configure a network interface on the Linux system.
284
   View all the interfaces along with status.
285
   $ ifconfig -a
286
   Start or stop a specific interface using up and down command as shown below.
287
   $ ifconfig eth0 up
288
   $ ifconfig eth0 down
289
37. uname command examples
290
   Uname command displays important information about the system such as - Kernel name, Host name, Kernel release number,
291
   Processor type, etc.,
292
   Sample uname output from a Ubuntu laptop is shown below.
293
   $ uname -a
294
   Linux john-laptop 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19 01:12:52 UTC 2010 i686 GNU/Linux
295
38. whereis command examples
296
   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.
297
   $ whereis ls
298
   ls: /bin/ls /usr/share/man/man1/ls.1.gz /usr/share/man/man1p/ls.1p.gz
299
   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.
300
   $ whereis -u -B /tmp -f lsmk
301
   lsmk: /tmp/lsmk
302
39. whatis command examples
303
   Whatis command displays a single line description about a command.
304
   $ whatis ls
305
   ls           (1)  - list directory contents
306
 
307
   $ whatis ifconfig
308
   ifconfig (8)         - configure a network interface
309
40. locate command examples
310
   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.
311
   The example below shows all files in the system that contains the word crontab in it.
312
   $ locate crontab
313
   /etc/anacrontab
314
   /etc/crontab
315
   /usr/bin/crontab
316
   /usr/share/doc/cron/examples/crontab2english.pl.gz
317
   /usr/share/man/man1/crontab.1.gz
318
   /usr/share/man/man5/anacrontab.5.gz
319
   /usr/share/man/man5/crontab.5.gz
320
   /usr/share/vim/vim72/syntax/crontab.vim
321
41. man command examples
322
   Display the man page of a specific command.
323
   $ man crontab
324
   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.
325
   $ man SECTION-NUMBER commandname
326
   Following 8 sections are available in the man page.
327
   1.   General commands
328
   2.   System calls
329
   3.   C library functions
330
   4.   Special files (usually devices, those found in /dev) and drivers
331
   5.   File formats and conventions
332
   6.   Games and screensavers
333
   7.   Miscellaneous
334
   8.   System administration commands and daemons
335
   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.
336
   $ whatis crontab
337
   crontab (1)          - maintain crontab files for individual users (V3)
338
   crontab (5)          - tables for driving cron
339
 
340
   $ man 5 crontab
341
42. tail command examples
342
   Print the last 10 lines of a file by default.
343
   $ tail filename.txt
344
   Print N number of lines from the file named filename.txt
345
   $ tail -n N filename.txt
346
   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.
347
   $ tail -f log-file
348
   More tail examples: 3 Methods To View tail -f output of Multiple Log Files in One Terminal
349
43. less command examples
350
   less is very efficient while viewing huge log files, as it doesn't need to load the full file while opening.
351
   $ less huge-log-file.log
352
   One you open a file using less command, following two keys are very helpful.
353
   CTRL+F - forward one window
354
   CTRL+B - backward one window
355
   More less examples: Unix Less Command: 10 Tips for Effective Navigation
356
44. su command examples
357
   Switch to a different user account using su command. Super user can switch to any other user without entering their password.
358
   $ su - USERNAME
359
   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.
360
   [john@dev-server]$ su - raj -c 'ls'
361
 
362
   [john@dev-server]$
363
   Login to a specified user account, and execute the specified shell instead of the default shell.
364
   $ su -s 'SHELLNAME' USERNAME
365
45. mysql command examples
366
   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.
367
   To connect to a remote mysql database. This will prompt for a password.
368
   $ mysql -u root -p -h 192.168.1.2
369
   To connect to a local mysql database.
370
   $ mysql -u root -p
371
   If you want to specify the mysql root password in the command line itself, enter it immediately after -p (without any space).
372
46. yum command examples
373
   To install apache using yum.
374
   $ yum install httpd
375
   To upgrade apache using yum.
376
   $ yum update httpd
377
   To uninstall/remove apache using yum.
378
   $ yum remove httpd
379
47. rpm command examples
380
   To install apache using rpm.
381
   # rpm -ivh httpd-2.2.3-22.0.1.el5.i386.rpm
382
   To upgrade apache using rpm.
383
   # rpm -uvh httpd-2.2.3-22.0.1.el5.i386.rpm
384
   To uninstall/remove apache using rpm.
385
   # rpm -ev httpd
386
48. ping command examples
387
   Ping a remote host by sending only 5 packets.
388
   $ ping -c 5 gmail.com
389
49. date command examples
390
   Set the system date:
391
   # date -s "01/31/2010 23:59:53"
392
   Once you've changed the system date, you should syncronize the hardware clock with the system date as shown below.
393
   # hwclock -systohc
394
 
395
   # hwclock --systohc -utc
396
50. wget command examples
397
   The quick and effective method to download software, music, video from internet is using wget command.
398
   $ wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.2.1.tar.gz
399
   Download and store it with a different name.
400
   $ wget -O taglist.zip http://www.vim.org/scripts/download_script.php?src_id=7701
401
 
402
 

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.