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Difference between '.*' and .* in grep

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# 1  
Old 01-15-2010
Difference between '.*' and .* in grep
Hi

What is the difference between grep '.*' xx and grep .* xx?
What grep .* xx command will do where xx is file name.

Thanks

Sas
# 2  
Old 01-15-2010
They have completely different meanings
Code:
grep '.*' xx

means print any line from the file xx that contains 0 or more characters. It is equivalent to
Code:
grep '' xx

or just:
Code:
cat xx

Code:
grep .* xx

will only work if there is exactly one file present in the directory that starts with a . and that contains no spaces of special characters. The command will then grep that file name in the file xx and print the lines that contain the part of the file name after the dot preceded by any character.

Neither are useful commands.
# 3  
Old 01-15-2010
Thanks for your reply..

My xx file contains

Code:
[/home/trg_ux/saswata]cat xx

total 32

-rw-r-----   1 trg_ux     users            0 Jan 15 11:06 xx

-rw-r-----   1 trg_ux     users         1118 Jan 15 10:53 yy

-rw-r-----   1 trg_ux     users           29 Jan 14 15:34 datelst.lst

-rw-r-----   1 trg_ux     users          378 Jan 14 14:56 path.lst

-rw-r-----   1 trg_ux     users           84 Jan 14 14:35 dept.lst

-rw-r-----   1 trg_ux     users          248 Jan 14 14:19 emp.lst

-rw-r-----   1 trg_ux     users            3 Jan 13 11:26 devnull

-rwxr-x---   1 trg_ux     users          403 Jan 13 11:25 prob14.15.sh

-rwxr-x---   1 trg_ux     users          139 Jan 13 11:07 LF

drwxr-x---   2 trg_ux     users         1024 Jan 12 18:24 test1

-rwxr-x---   1 trg_ux     users          139 Jan 12 18:22 lf

-rw-r-----   1 trg_ux     users            0 Jan 12 17:31 tr

drwxr-x---   2 trg_ux     users         1024 Jan 11 18:04 test2

-rwxr-x---   1 trg_ux     users          187 Jan 11 18:03 prob15.11.sh

-rw-r-----   1 trg_ux     users          215 Jan 11 13:35 filenames

-rwxr-x---   1 trg_ux     users          159 Jan 11 13:32 prob14.10.sh

-rwxr-x---   1 trg_ux     users          135 Jan 11 11:26 prob14.sh

when i run command it shows following output.

Code:
[/home/trg_ux/saswata]grep .* xx
..:, ¸D*°dä¤lTÐ0MQ.cshrcMR.exrcMS.loginM.profile
                                                .sh_history@hanilniGã
.ksh_history_history@biswajit@kkrishna@lTRAINER@ëmahuya@{       mentoringeRtPriyankaRÉ007hhnRö
                                                                                              Ddatedisp.shR÷øfunc.shtfiRømain.shRüxmanish@`saswatas_nGHÀtestprmyerromyfilesmyfilexyztt2a?can.file1tfile2eexaple_01xexamplecabexamNT.historyexam1tSMemp.shPGsatyakiloexam3janshtraining_kshmylistdead.letterumitraining_ksh.gza1.txt.bkparunavaa2.txt.bkpanupamdipushbidhantsa3.txt.bkp.dipabc.txt.b¼ ¼abhi.txt.bkpchhi.txt.bkpmanls.txt.bkpnmanwc.txt.bkptluna.txtunixtrparo.txt.bkpproggma.txt.bkpsatabdi.txt.bkpsky.txt.bkpsneha.txt.bkpsh.shasgn.shassgn.sha.txtllldate.shMousumibid_deb_suvTest_pp1.shgrouphimadri_adhiraj_shoumikgoutam_tuhinA14mousumi_joydeepA14.txtprob1.shJOYDEEP_MOUSUMIdeb1.txtA16.txtBidhan_Debajyoti_Suvrajitsss.txtA14.txt.bkpA16.txt.bkpa.txt.bkpdeb1.txt.bkpluna.txt.bkpsss.txt.bkpsnehatanushreejoydeepHello.jav¼ ¼Sneha_TestAnupamAvijitArunavaArnabsneha_tanushree_satabdi_poulomi_joydeep_mousmitanushree_sneha_satabdi_poulomi_joydeep_mousmisneha_satabdi_tanushree_poulomi_mousmi_joydeeppoulomi_sneha_tanushree_satabdi_joydeep_mousmiAnupam_Avijit_Arunava_Arnabass2.cppass2.oa.outmydirapratimDBCankKSllDBC1mykkchinkiiichidiff.sh1.txt2.txtvishaldTC++rutmpsttmrctry1Test.cpptemperature.cppfresher_janjanabhi
.sas:xx
xx:
xx:total 32
xx:-rw-r-----   1 trg_ux     users            0 Jan 15 11:06 xx
xx:-rw-r-----   1 trg_ux     users         1118 Jan 15 10:53 yy
xx:-rw-r-----   1 trg_ux     users           29 Jan 14 15:34 datelst.lst
xx:-rw-r-----   1 trg_ux     users          378 Jan 14 14:56 path.lst
xx:-rw-r-----   1 trg_ux     users           84 Jan 14 14:35 dept.lst
xx:-rw-r-----   1 trg_ux     users          248 Jan 14 14:19 emp.lst
xx:-rw-r-----   1 trg_ux     users            3 Jan 13 11:26 devnull
xx:-rwxr-x---   1 trg_ux     users          403 Jan 13 11:25 prob14.15.sh
xx:-rwxr-x---   1 trg_ux     users          139 Jan 13 11:07 LF
xx:drwxr-x---   2 trg_ux     users         1024 Jan 12 18:24 test1
xx:-rwxr-x---   1 trg_ux     users          139 Jan 12 18:22 lf
xx:-rw-r-----   1 trg_ux     users            0 Jan 12 17:31 tr
xx:drwxr-x---   2 trg_ux     users         1024 Jan 11 18:04 test2
xx:-rwxr-x---   1 trg_ux     users          187 Jan 11 18:03 prob15.11.sh
xx:-rw-r-----   1 trg_ux     users          215 Jan 11 13:35 filenames
xx:-rwxr-x---   1 trg_ux     users          159 Jan 11 13:32 prob14.10.sh
xx:-rwxr-x---   1 trg_ux     users          135 Jan 11 11:26 prob14.sh
[/home/trg_ux/saswata]PuTTY

Can you tell me why such a output is displaying
Last edited by pludi; 01-15-2010 at 04:32 AM.. Reason: code tags, please...
# 4  
Old 01-15-2010
You are also grepping inside files / directories that start with a dot. It is not a useful command. You should not use it. What are you trying to accomplish?
# 5  
Old 01-15-2010
Or explained anther way:

.* will glob - be expanded to a list of files that have a leading dot in the filename

'.*' is a regular expression when used as an argument to grep

* is a shell metacharacter, '*' is just an asterisk character which has to be interpreted by a program other than the shell if it is going to have a special meaning.
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