UNIX TIPS

Notes taken from daily job. These are the most commonly used when i'm with unix shell.
I know these things are not in the order and etc.. I just maintained the order i explored these options 

Please fell free to feedback if any issues

1) Is there a way where we can get some feedback once a command is executed in shell. Like 1/0 ..etc ??

UNIX>cd vij_test_dir

vij_test_dir: No such file or directory.

UNIX> echo $?

1

UNIX> mkdir vij_test_dir

UNIX>cd vij_test_dir

UNIX>echo $?

0

UNIX>cd vijay_test

after every command try : echo $?

if 0 ==> success

if nonzero ==> failed

2) How to copy from once machine to another machine without logging in?

UNIX> scp user_name@unix0420:/tmp/user_name/fmly_latest_local_gdsgen/  ./

UNIX> scp fmci201356.fm.intel.com:/tmp/user_name/a.ot ./

##this will be more faster (if we have data in specific machine/or use scp based on a specific login in which we already have a session running)

3) How to monitor the end of log file always (file which is getting a log dump from a run which is in progress)

  UNIX> tailf <FILE_NAME>

4) How to check for any syntax errors in a perl script ?

UNIX> perl -c <program_file>

5) Cron job : to run any job automated or overnight job fires ?

Cron jobs are machine specific, If we create a cron job on say machine "abc123" : then we should log into to "abc123" machine (ssh abc123) and then udpate as required.

Having said that you won’t be able to see your own cron jobs of machine abc123 without doing "ssh" to abc123 machine.

UNIX> crontab -e

Syntax:

0 8 * * 1-5 <file_which_has_list_of_commands>

This is like execute the script at 8am sharp (8am 0 min  1-5 means five days a week)

Eg:

UNIX> crontab -e

0 8 * * 1-5 <file_which_has_list_of_commands>

Save and exit ==> this will run the script on five days at 8am forever

6) How to monitor stale data (in GB) by a specific user ?

stodstatus storage-users --fields "User,Path,Usage/1024,Age180/1024" "User=='user_name'&&Age180>'10'"

7) copy command ?

How to copy real content instead of symbolic links while performing copy operations on a database which has links ?

  UNIX> cp -rHL <directory_name> .

UNIX> cp - u  --> will only copy files that don't exist, or are newer than their existing counterparts, in the destination directory.

8) One-Line Technique for Mailing a File's Contents ?

If you have a file called apple.txt and you want to mail its contents as a mail message to nobody@december.com with the subject line "unix-asg1,"

you can do this at the Unix prompt like this:

mail -s "unix-asg1" nobody@december.com < apple.txt

This is very useful if you are a Unix shell and you don't want to enter your mail program.

Note: this may not work on all Unix systems. If this doesn't work, follow this example to mail a file's contents.

A One-Line Technique for a Mailing a Short Message

You can use the echo command to send a short text message in one line. 

Say you want to send the message "City Hall 1pm" to nobody@december.com with the subject line "meeting today" by email. 

You can do it at the Unix prompt like this:

echo "City Hall 1pm" | mail -s "meeting today" nobody@december.com

9) How to cutout first column or till first : comes and prints the rest to std out ?

cut -f 1 -d ":" –complement

10) To keep a banner like below in unix use "banner" command and arguments following:

UNIX> banner malli

#     #     #     #        #        ### 

##   ##    # #    #        #         #  

# # # #   #   #   #        #         #  

#  #  #  #     #  #        #         #  

#     #  #######  #        #         #  

#     #  #     #  #        #         #  

#     #  #     #  #######  #######  ### 

11) Copy all but except one directory  ?

UNIX> cd source_path

UNIX> cp -rv `ls -A source_path | grep -vE "directory to be excluded | source_path"`  destination_path

eg: source_path --> /tmp/amallika/delete

    destination_path -->  /tmp/amallika/temp

    cp -rv `ls -A /tmp/amallika/delete | grep -vE "dbs|/tmp/amallika/delete"` /tmp/amallika/temp

12) To use date command inside echo: (nested commands)

UNIX> echo `date`

`date` will just return the output of the date command. However, it removes extra space characters at places where there are more than one consecutive space characters in the output.

In "`date`", the double quotes are weak quotes, so they will expand variables (try "$PWD") and perform command substitution.

In '`date`', the single quotes are stronger quotes, so they will not allow expansion of variables or command substitution within them.

Example :

UNIX> echo '$PWD'

$PWD

UNIX> echo "$PWD"

/tmp/amallika/delete

13) CTRL + L ==> clears the screen (same as clear)

14) wc command ?

wc has options to only show character (-c), word (-w), or line (-l) counts.

Example of a file user_name:

UNIX> wc user_name

648   5190 132507 user_name

UNIX> wc -l user_name

648 user_name

UNIX> wc -c user_name

132507 user_name

UNIX> wc -w user_name

5190 user_name

15) AWK command ? 

Awk is one of the most powerful tools in Unix used for processing the rows and columns in a file. 

Awk has built in string functions and associative arrays.

Awk supports most of the operators, conditional blocks, and loops available in C language.

One of the good things is that you can convert Awk scripts into Perl scripts using a2p utility. 

The awk variable $1 contains the first field in a record, $2 the second, $3 the third, etc. $0 contains all fields.

To print second last and last field respectively: $(NF-1)and $(NF). NF signifies the number of fields

Eg: awk 'BEGIN {start_action} {action} END {stop_action}' filename

  Here the actions in the begin block are performed before processing the file and the actions in the end block are performed after processing the file. The rest of the actions are performed while processing the file.

  UNIX> awk '{print $1}' file_name > amr

This will print only 1st column of the file into the amr file

This will print 3rd and 6th columns only  :  

UNIX> awk ‘{print $3,$6}’ file_in > file_out

##in awk use  below options format

conditions { actions }

##use a following sample to illustrate the above command

UNIX> awk '$1 ~ /[0-9]/ {print $0}' test

asdfdsafdsa(123)432-1421(432)412-34321vasdf

kjhkjh(123)432-143214asdf

## if there is a string with "arjun:malli" in the second column of a file "test.rpt"

UNIX> awk '{print $2}' test.rpt |  awk -F :  '{print $1'

This will give output as arjun

FS or -F is a field separator option of AWK that can be used to filter based on specific fields.. Like in the above example using :

To sum contents in column using awk:

UNIX> awk '{sum += $1} END {print sum}' delete

3830

To print even lines from a file

UNIX> awk 'NR % 2 ' file_name

16) top command ?

# Print  system usage and top resources hogs

UNIX> top

Then use "z" to toggle the coloring of this result

17) ZIP related ?

"gzip" or "gzip -r"  ==> compresses

"gunzip" "gunzip -r" ==> decompresses.

(gunzip is the same as gzip -d)

Examples: 

UNIX> ls logs

a.log b.log

UNIX> gzip logs

gzip: logs is a directory -- ignored

UNIX> gzip -r logs

UNIX> gunzip logs/

gzip: logs/ is a directory -- ignored

UNIX> gunzip -r logs/

18) We can create a function in .cshrc file to do the repetitive tasks !!

i) Like to change the file to executable and also to add a comment in that file

##add the below lines in .cshrc file

function  func_add_cmnt_chgrp {

sed -i  '1s/^/#!\/usr\/bin\/perl\n\n/' $1

chmod  +x $1

chgrp -R impr_group *

}

19) \ operator ?

It can be used as a command extension into next line in UNIX awk/sed etc.. commands.

Also \ can be used in tcl as command extension into next line.

20) cat and tac !! ??

UNIX> cat test.log

--> contents are printed on prompt in regular order (first line to last line)

UNIX> tac test.log

--> contents are printed on prompt in reverse order (last line to first line) 

--> page through a log file in reverse to avoid guessing number of lines to tail

21) dos file format to unix file format ? if there any file format issues once you copied it from windows environment ?

UNIX> dos2unix file_name

To remove ^M  kind of dummy char when a file is exported from windows to unix

22) process status command options (ps ) ?? 

PS [process status] :

To see every process on the system using standard syntax:

  ps -e

  ps -ef

  ps -eF

  ps -ely

To see every process on the system using BSD syntax:

  ps ax

  ps axu

To print a process tree:

  ps -ejH

  ps axjf

To get info about threads:

  ps -eLf

  ps axms

To get security info:

  ps -eo euser,ruser,suser,fuser,f,comm,label

  ps axZ

  ps -eM

To see every process running as root (real & effective ID) in user format:

  ps -U root -u root u

To see every process with a user-defined format:

  ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm

  ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm

  ps -eopid,tt,user,fname,tmout,f,wchan

Print only the process IDs of syslogd:

  ps -C syslogd -o pid=

Print only the name of PID 42:

  ps -p 42 -o comm=

commands to identify the particular tool and kill/manage

 ps -elf | grep user_name | grep gena

 ps -elf | grep user_name | grep w

 ps -elf | grep user_name

23) g and Esc+P @ UNIX SHELL will give the recent history of commands that start with g

24) SED (stream line editor ) ?

##This will delete the lines whick are having(corresponding) abc in the clk.tcl file

sed –i ‘/abc/d’ clk.tcl

## This will delete every 2nd line starting from 2ndline##

sed '2~2d' temp2 > temp3

## this will delete the 3rd line from the file temp2

sed 3d temp2

###Remove the interval between lines 7 and 9:

sed '7,9d' filename.txt

####Remove the line containing the string "awk":

sed '/awk/d' filename.txt

###Remove the last line:

sed '$d' filename.txt

###Remove all empty lines:

sed '/^$/d' filename.txt      

sed '/./!d' filename.txt

###Remove the line matching by a regular expression (by eliminating one containing digital characters, at least 1 digit, located at the end of the line):

sed '/[0-9/][0-9]*$/d' filename.txt

  Some more SED  examples :

• With and Without -n option:

UNIX> ls -l | sed -e '/^d/ p'

total 184

-rwxr-x--- 1 user_name coe73 91636 2015-04-17 14:07 test.tcl

drwxr-x--- 8 user_name coe73 12288 2015-06-03 23:21 lane_new_fp_expt

drwxr-x--- 8 user_name coe73 12288 2015-06-03 23:21 lane_new_fp_expt

-rwxr-x--- 1 user_name coe73    28 2015-06-21 20:27 sed.in

-rwxr-x--- 1 user_name coe73   864 2015-06-19 22:11 xaa

UNIX> ls -l | sed -n -e '/^d/ p'

drwxr-x--- 8 user_name coe73 12288 2015-06-03 23:21 lane_new_fp_expt

By default sed will print all lines to stdout if we use -e. But if you want to see specific lines that were matched using the

regexp use -n.

Other SED examples:

UNIX> sed -e '/pattern/ command' file_name

Command can be s (search & replace), d (Delete), p (print) , i(insert) & a (append)

Ex :

To delete all lines in a file that are starting with #

UNIX> sed -e '/^#/ d' file_name ;

Make of use SED/AWK extensively when the files are big. Since opening vim/another editor and doing that is bit difficult/time consuming

To delete 1 to 100 lines in a file

UNIX> sed -e '1,100 d' file_name

To delete 11  to  end of file (EOF)

UNIX> sed -e '11,$ d' file_name

Capitalize all vowels in a file:

UNIX> sed 'y/aeiou/AEIOU/' somefile

Example of cat and sed :

UNIX> cat 1

freeze ing life yaar:wq

hello hello

hello :wq

bolo i am vccsus_1p05

UNIX> sed -e 's/hello/malli/' 1

freeze ing life yaar:wq

malli hello

malli :wq

bolo i am vccsus_1p05

UNIX> sed -e 's/hello/malli/g' 1

freeze ing life yaar:wq

malli malli

malli :wq

bolo i am vccsus_1p05

==> -e will just gives us -echo output on the screen and we can redirect this to a new file.

But if you want to modify the file "1" on the fly (like overwriting) then you should use -I (inplace option of sed)

UNIX> sed -i 's/hello/malli/' 1

UNIX> cat 1

freeze ing life yaar:wq

malli hello

malli :wq

bolo i am vccsus_1p05

##to replace a 10 digit number in the telephone notation format:

##that is to replace 9986535417 as (998)653-5417

UNIX> sed -i 's/\([0-9]\{3\}\)\([0-9]\{3\}\)\([0-9]\{4\}\)/(\1)\2-\3/g' test

##to trim leading edge white space using sed

UNIX> sed -i 's/^[ \t]*//g' test

##to trim trailing whitespaces in a file

UNIX> sed -i 's/[ \t]*$//g' test

## to trim both leading and trailing whitespaces using single line sed command

UNIX> sed -i 's/^[ \t]*//g;s/[ \t]*$//g' test

We can use tow reg exp in '' of sed using ; this operator

##how to add a comment in another file from unix using sed.

##1 ==> first line of the file

UNIX> cat test

aiasdfdsafdsamalliasdf

asdfdsafdsa(123)432-1421(432)412-34321vasdf

kjhkjh(123)432-143214asdf

UNIX> sed '1s/^/\#\# this is comment \#\#\n/' test

## this is comment ##

aiasdfdsafdsamalliasdf

asdfdsafdsa(123)432-1421(432)412-34321vasdf

kjhkjh(123)432-143214asdf

##to delete all blank lines

UNIX> sed -i '/^$/ d' test

##to delete all lines containing malli in a file called test

UNIX> sed -i '/malli/ d' test

##to delete lines starting with ##

UNIX> sed -i '/^##/ d' test

##to delete first two lines in a file

UNIX> sed -i '1,2 d ' test

--> Change the third 'apple' in each record to 'orange': sed 's/apple/orange/3' somefile

25) How to open pdf in unix ?

UNIX> xpdf file_name

26) How to open a png or an image file ?

UNIX> display file_name

27) How to untar a file ? 

UNIX> tar –zxvf filename.tar.gz:

-z : Uncompress the resulting archive with gzip command.

-x : Extract to disk from the archive.

-v : Produce verbose output i.e. show progress and file names while extracting files.

-f data.tar.gz : Read the archive from the specified file called data.tar.gz.

28) How to display a folder size ? 

UNIX>du -sk folder/file_name

Esc+b to go to one word back in the terminal

Esc+f to go one word forward

To see the memory occupied per user

UNIX> du -skH *

24) kill,fg & bg commands :

UNIX> kill jobID

UNIX> kill %% ; # To kill the the most recent from the many Jobs that are running under the hood

UNIX> jobs   ; # This lists out current active process in the terminal

UNIX> fg [1] or fg %1 ; # To resume/ go to the job1 (fore ground --> fg)

UNIX> bg ; # To run job in background (bg) 

UNIX> bg %jobid

UNIX> kill %jobid

UNIX> kill -9 %jobid ; ##use -9 if a job refuses to be killed

25) "diff" command in UNIX ??

To compare files line by line and it can compare even the directories too

UNIX> diff -ri FILE1 FILE2

diff has got lot of options…

UNIX> diff file1 file 2  ; #to do simple file diff

Go through the list of options that diff has got in the below table..

UNIX> diff file_1 file_2

UNIX> diff -qr DIR_1 DIR_2

EXAMPLS :

UNIX> diff -qr  SD4_RTL1P0_WW15P2_v1p16 SD4_RTL1P0_WW16P5_v1p17

Only in SD4_RTL1P0_WW15P2_v1p16: testfamilyewtop.syn_final.upf

Files SD4_RTL1P0_WW15P2_v1p16/testfamilyewtop.syn_final.vg and SD4_RTL1P0_WW16P5_v1p17/testfamilyewtop.syn_final.vg differ

Only in SD4_RTL1P0_WW16P5_v1p17: testfamilyewtop_DC_OUTPUT.upf

26) !$ use in UNIX ??

UNIX> ls amr/test.txt

UNIX> gvim !$

(will open the test.txt file in the gvim editor)

UNIX> ls amr/

UNIX> gvim !$

(will open the a new file with name amr in the gvim editor)

27) du command ??

UNIX>  du –sk folder name  ### this will give the amount of memory occupied by the folder

28) Is there a way to change vnc resolution ?

"xrandr" command does that

UNIX> xrandr -s 1920x1200; #number changes based on lap configuration

29) Interactive editor and navigator ?

UNIX> j ; #It opens a windows based look for your work area

30) Office program in unix ?

UNIX> soffice a.csv &

31) To know which is the host machine that you are using currently (like SLES-10 or SLES-11)

UNIX>  cat /etc/SuSE-release

SUSE Linux Enterprise Server 10 (x86_64)

VERSION = 10

PATCHLEVEL = 3

32) lscpu  ??

It gathers CPU architecture information form /proc/cpuinfon in human-read-able format:

UNIX> lscpu

Sample outputs:

Architecture:          x86_64

CPU op-mode(s):        32-bit, 64-bit

Byte Order:            Little Endian

CPU(s):                8

On-line CPU(s) list:   0-7

Thread(s) per core:    1

Core(s) per socket:    4

CPU socket(s):         2

NUMA node(s):          1

Vendor ID:             GenuineIntel

CPU family:            6

Model:                 15

Stepping:              7

CPU MHz:               1866.669

BogoMIPS:              3732.83

Virtualization:        VT-x

L1d cache:             32K

L1i cache:             32K

L2 cache:              4096K

NUMA node0 CPU(s):     0-7

33) If you are facing a problem of copy/paste not working between linux and windows through VNC,

you can run below command in linux terminal. It will work fine.  Command to be run on linux terminal is: 

UNIX> vncconfig –nowin&.

34) In reg exp : Paentheses have the side effect of capturing, setting \1 to the stuff matched by the first set of parentheses, \2 to the second, etc.

 gzip -c large.log | ssh user@hostwithbigdisk 'cat > /dir/large.log.gz' # Compress and ssh transfer a log that has filled a filesystem.

zcat large.log.gz | awk '{print $0 | "gzip -v9c > large.log-"$1"_"$2".gz"}' # Breakup compressed log by syslog date and recompress. #awksome

35) To find the memory used by me in unix :

UNIX> df -kh ~user_name

Filesystem            Size  Used Avail Use% Mounted on

innfs031:/vol/vol6/ba_ctg_home01/user_name

                      50G   46G  4.8G  91% /nfs/iind/home/user_name

UNIX> df -kh . -P

Filesystem            Size  Used Avail Use% Mounted on

incfs02n03b-14:/mg_disk1652  501G  436G   65G  88% <disk_name>

36) Diff b/w the directories and finding only the differences :

UNIX> diff -r -q OLD_DIR NEW_DIR | grep differ | grep -v "verif/" ; #to find diff and with verif directory names

37) To get absolute directory name with ls, enter in the terminal's command shell:

UNIX> ls -ld $PWD/*

Also use this :

UNIX> ls -tlr <dir_name>/*.upf

-rwxr-x--- 1 mn1 coe73   4875 Sep  9 11:16 <dir_name>/master.upf

-rwxr-x--- 1 mn1 coe73   4797 Sep  9 11:16 <dir_name>/slave6.upf

ls -t to get only list(no time stampings etc..)

38) string replacement in unix ?

1. Replacing one string with another in all files in the current directory:

These are for cases where you know that the directory contains only files and that you want to process all files.

If that is not the case, use the approaches in 2.

a. Non recursive, files in this directory only:

UNIX> sed -i 's/foo/bar/' *

UNIX> perl -i -pe 's/foo/bar/' *

b. Recursive, files in this and all subdirectories

UNIX> find . -type f -print0 | xargs -0 -exec sed -i 's/old/new/g'

c. try exploring "rename" command

39) Creating a soft link to the files ?

UNIX> ln -s <FILE_NAME>  soft_link

40) Echo :

Your shell is interpreting the quotes, both ' and ", before they even get to echo. I generally just put double quotes around my argument to echo even if they're unnecessary; for example:

$ echo "Hello world"

Hello world

So in your first example, if you want to include literal quote marks in your output, they either need to be escaped:

$ echo \'Helloworld\'

'Hello world'

Or they need to be used within a quoted argument already (but it can't be the same kind of quote, or you'll need to escape it anyway):

$ echo "'Hello world'"

'Hello world'

$ echo '"Hello world"'

"Hello world"

41) sort ??

--> Sort based on column : UNIX> sort -k2  -n FILE

42) ls command options ?

UNIX> ls

bye  hai  help

To find out which of the items are files and which are directories, we can specify the -F option to ls

UNIX> ls -F

bye  hai  help/

UNIX> ls

bye  hai  help

1 file per line

UNIX> ls -1

bye

hai

help

43) head and tail commands ?

To print first few lines of a file to stdout

UNIX> head file_name

To print first 5 lines of a file to stdout

UNIX> head -5 file_name

To print last few lines of a file to stdout

UNIX> tail file_name

To print last 5 lines of a file to stdout

UNIX> tail -5 file_name

44) File redirect operators:

">" symbol is used to redirect the stdout to a file

">>" to append to an already existing file

"<" symbol is used to read a file content

UNIX > sort < in_file > out_file

and

UNIX > sort in_file > out_file

Both of the above commands are same

45) username of the host ?

UNIX> whoami

user_name

46) To find who is on system with you:

UNIX> who

user_name pts/21       2015-04-27 10:18

user_name pts/22       2015-04-28 16:23

sdayyaga pts/23       2015-04-01 10:29

guptaabx pts/24       2015-05-19 15:55

47) To know one line man detail of a command use "whatis"

UNIX> whatis wc

wc (1)               - print the number of newlines, words, and bytes in files

wc (1p)              - word, line, and byte or character count

48) To give ar/w permissions to all :

chmod a+rw file_name

To remove r/w/x permissions for others and group

chmod go-rwx file_name

One can also  "chmod 777 file_name " or "chmod go+rwx file_name" to give every permissions to everyone else

49) To check your current quota and how much of it you have used ??

UNIX> quota -v

50) df (disk fragmentation) : 

To find out how much space left on the current disk(file server) use

UNIX> df .

Filesystem           1K-blocks      Used Available Use% Mounted on

infs5576b:/vol16/mg_disk1573

                    314572800 247701504  66871296  79% /nfs/iind/disks/mg_disk1573

To get the details in readable format use -kh to the above command

UNIX> df -kh .

Filesystem            Size  Used Avail Use% Mounted on

infs5576b:/vol16/mg_disk1573

                     300G  237G   64G  79% /nfs/iind/disks/mg_disk1573

51) du(disk usage):

To get the number of KB used by each subdirectory. Very useful to find out who or which file is occupying more disk space

-s means display summary

-kh  or -h ===> to get human readable format

UNIX> du -skh *

304K    SD4_RTL1P0_WW15P2_v1p16

304K    SD4_RTL1P0_WW16P5_v1p17

79G     SD4_RTL1P0_WW18P2_v1p18

52) How to read file content when the file is in zipped format ?

This will scroll the whole text so fast if the file content is huge

UNIX> zcat file_name.gz

If want to read page by page slowly .. Use | less

UNIX> zcat file_name.gz | less

53) To report all files in a directory use "file *". This will give you the file format for each file in that directory

UNIX> pwd

/nfs/iind/home/user_name

UNIX> file *

CDS.log.cdslck:         ASCII text

Desktop:                directory

procs.tcl:          ASCII English text

alias_dc_icc.tcl:       ASCII English text, with CRLF line terminators

del_dsslog.sh:          Bourne-Again shell script text

54) history command ?

UNIX> set history=1000

UNIX> echo $history

1000

UNIX> !! (recall last command)

UNIX>!-3 (recall 3rd most recent command)

UNIX>!5 (recall 5th command in the list)

UNIX>!grep (recall last command starting with grep)

55) find command ? 

To search for all files with extensions .txt starting from the current directory and through all the subdirectories , then printing the name of the file to the screen

UNIX> find .-name "*.txt" -print

To find all files over 1MB size and display the result as a long listing , type:

UNIX> find .-size +1M ls

find * -type f -name "*.sp"

##to find the all .sp files recursively

UNIX> find . –name filename ##normal find command

56) date ?? 

--> To print out current date

UNIX> date

Sun May 31 20:16:21 IST 2015

UNIX> cal month year

UNIX> cal 5 2015

     May 2015

Su Mo Tu We Th Fr Sa

               1  2

3  4  5  6  7  8  9

10 11 12 13 14 15 16

17 18 19 20 21 22 23

24 25 26 27 28 29 30

31

57)  who, finger are  UNIX commands to know who are all logged into my computing machine

58) calculator ??

UNIX>xcalc & ;

##make use of this for calculating purpose…don’t go to windows every other time to use calc.. (also try expr in SNPS tools too )

59) Getting bored..??? 

Try UNIX > xfig & ;  

or 

UNIX> xpaint &;

#will open up a drawing program

60) You can actually try using sometime gnuplot to plot the graphs etc.. 

UNIX> gnuplot &

61) logout / exit ?

UNIX > logout ; 

UNIX> exit ; ##to quit a UNIX shell

62) tar command ?? 

Unix tar command line options

In this section of UNIX tar command tutorial we will see some useful options of tar command in Linux and we will use this options on our example to understand usage of this option along-with tar command.

c -- create, for creating tar file

v -- verbose, display name of files including,excluding from tar command

f -- following, used to point name of tar file to be created. it actually tells tar command that name of the file is "next" letter just after options.

x -- extract, for extracting files from tar file.

t -- for viewing content of tar file

z -- zip, tells tar command that create tar file using gzip.

j –- another compressing option tells tar command to use bzip2 for compression

r -- update or add file or directory in already existed .tar file

wildcards -- to specify patters in unix tar command

##to create a .tar for a directory abc/

UNIX> tar -cvf abc.tar abc/

##to create a .tar.gz for a directory abc/ (more compressed than .tar)

UNIX> tar -cvzf abc.tar abc/

##to unzip/de compress the folder abc.tar.gz

UNIX> tar -xvf abc.tar.gz

63) How to update my password ?

UNIX>passwd ; ##to change the password

64) "comm" command ??

UNIX > comm FILE_1 FILE_2

This will print output in 3 columns

1st ==> which are only in FILE_1

2nd column ==> which are only in FILE_2

3rd column ==> which are in both files

##we can suppress the unwanted columns by specifying them in the command line as in below examples

Examples:

##to see only the things common to both files (i.e column 3)

UNIX> comm -12 FILE_1 FILE_2

##to see the list which only present in FILE_1

UNIX> comm -23 FILE_1 FILE_2

##to see the list which only present in FILE_2

UNIX> comm -13 FILE_1 FILE_2

65) regexp in unix ?

\s matches white space, i.e. space, tab, newline, etc. Example: /foot\s+ball/ matches 'foot ball' but not 'football'.

\W matches any non-word character, anything \w doesn't match.

* means zero or more, + means one or more, ? means zero or one.

Parentheses and | denote options. Example: /(red|green|blue) truck/ matches 'red truck' or 'green truck' or 'blue truck'.

Parentheses have the side effect of capturing, setting \1 to the stuff matched by the first set of parentheses, \2 to the second, etc.

You can include comments inside a regex with (?# ... ). For example, /the\s+(?# One or more spaces)end

I will keep adding as and when i come across more useful daily tips