Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Problem with sed wildcard "*"
Top Forums UNIX for Dummies Questions & Answers Problem with sed wildcard "*" Post 302739425 by bakunin on Tuesday 4th of December 2012 07:36:51 AM
Old 12-04-2012
It is probably a problem in understanding, not in using:

Suppose you have a string

Code:
abc

and you want to match it, based on the "a" and the "c" occurring. You are looking for one occurrence of "a", followed by whatever, followed by one occurrence of "c". But if you look for "zero (or more) occurrences of 'a'", you basically don't care for the "a" at all - "zero or more" can also be "zero", which means there is no "a" there.

This begs the question what an expression like "a*" is good for, if it means that the "a" is optional at all. Well, suppose the following:

Code:
/xa*y/

This would match any "x", followed by zero or more "a"s, followed by "y". Strings matched by this would be:

Code:
xy
xay
xaaaaay
..etc.

Not matched would be:

Code:
xby
xbcdefy
xblablay
..etc.

In other words: our expression means that between "x" and "y" only "a"s are allowed - regardless how many, even zero - but if there is anything in between "x" and "y" it has to be "a"s and "a"s alone.

I hope this helps.

bakunin
 

10 More Discussions You Might Find Interesting

1. UNIX and Linux Applications

A question/problem about oracle "tns listener" and "enterprise manager"

hi, I have * an IBM P550 machine, * an AIX 5.3 running on it and * an oracle database, already installed on it. The problem (or question of my own) is: Oracle tns listener, "CT_LISTENER", and the enterprise manager (EM) of the instance, which is uniq instance and called... (0 Replies)
Discussion started by: talipk
0 Replies

2. UNIX for Advanced & Expert Users

A question/problem about oracle "tns listener" and "enterprise manager"

hi, I have a problem about the Oracle related components. I'm not able to find any answer yet, and waiting for your responses... Here is the configuration of my system: * an IBM P550 machine, * an AIX 5.3 running on it and * an oracle database, already installed on it. The problem (or... (1 Reply)
Discussion started by: talipk
1 Replies

3. Shell Programming and Scripting

cat $como_file | awk /^~/'{print $1","$2","$3","$4}' | sed -e 's/~//g'

hi All, cat file_name | awk /^~/'{print $1","$2","$3","$4}' | sed -e 's/~//g' Can this be done by using sed or awk alone (4 Replies)
Discussion started by: harshakusam
4 Replies

4. Shell Programming and Scripting

Simplify Bash Script Using "sed" Or "awk"

Input file: 2 aux003.net3.com error12 6 awn0117.net1.com error13 84 aux008 error14 29 aux001.ha.ux.isd.com error12 209 aux002.vm.ux.isd.com error34 21 alx0027.vm.net2.com error12 227 dux001.net5.com error123 22 us008.dot.net2.com error121 13 us009.net2.com error129Expected Output: 2... (4 Replies)
Discussion started by: sQew
4 Replies

5. Shell Programming and Scripting

awk command to replace ";" with "|" and ""|" at diferent places in line of file

Hi, I have line in input file as below: 3G_CENTRAL;INDONESIA_(M)_TELKOMSEL;SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL My expected output for line in the file must be : "1-Radon1-cMOC_deg"|"LDIndex"|"3G_CENTRAL|INDONESIA_(M)_TELKOMSEL"|LAST|"SPECIAL_WORLD_GRP_7_FA_2_TELKOMSEL" Can someone... (7 Replies)
Discussion started by: shis100
7 Replies

6. Shell Programming and Scripting

Using sed to find text between a "string " and character ","

Hello everyone Sorry I have to add another sed question. I am searching a log file and need only the first 2 occurances of text which comes after (note the space) "string " and before a ",". I have tried sed -n 's/.*string \(*\),.*/\1/p' filewith some, but limited success. This gives out all... (10 Replies)
Discussion started by: haggismn
10 Replies

7. Shell Programming and Scripting

how to use "cut" or "awk" or "sed" to remove a string

logs: "/home/abc/public_html/index.php" "/home/abc/public_html/index.php" "/home/xyz/public_html/index.php" "/home/xyz/public_html/index.php" "/home/xyz/public_html/index.php" how to use "cut" or "awk" or "sed" to get the following result: abc abc xyz xyz xyz (8 Replies)
Discussion started by: timmywong
8 Replies

8. Post Here to Contact Site Administrators and Moderators

Suggestion: adding two new groups "sed" and "awk"

Majority of the questions are pertaining file/string parsing w.r.t sed or awk It would be nice to have these two as their own sub category under shell-programming-scripting which can avoid lot of duplicate posts. (1 Reply)
Discussion started by: jville
1 Replies

9. Shell Programming and Scripting

Awk,sed : change every 2nd field ":" to "|"

Hi Experts, I have a string with colon delimited, want 2nd colon to be changed to a pipe. data: 101:8:43:4:72:14:41:69:85:3:137:4:3:0:4:0:9:3:0:3:12:3: I am trying with sed, but can change only 1 occurance: echo "101:8:43:4:72:14:41:69:85:3:137:4:3:0:4:0:9:3:0:3:12:3:" | sed 's/:/|/2'... (5 Replies)
Discussion started by: rveri
5 Replies

10. UNIX for Advanced & Expert Users

"GET" command retrieves multiple files while using wildcard

Hi All I am using GNU/Linux This is regarding the get command to retrieve files (filename with wild card characters) from remote server. I thought Get command can retrieve only 1 file irrespective of the files it has on the remote server And it is the function of mget to retrieve all... (7 Replies)
Discussion started by: sparks
7 Replies

LEARN ABOUT DEBIAN

fixnt

fixnt(1)							      Debian								  fixnt(1)

NAME

       fixnt - Filter for the Windows NT postscript printer driver.

SYNOPSIS

       fixnt < BADFILE.ps > GOODFILE.ps

DESCRIPTION

       The  Windows  NT  postscript  driver has a tendency to make broken postscript files, that are incompatible with psutils.  fixnt is a filter
       that fixes these problems, allowing the use of psnup(1).

       The filter takes the broken postscript file on stdin, and outputs a fixed postscript file on stdout.  It has no other form  for	invocation
       and takes no options on the command-line.

OPTIONS

       fixnt  takes no options.

BUGS

       fixnt does not check for NTPSOct94.  For a workaround, use a sed(1) command to replace 'NTPSOct94' with 'NTPSOct95', like so:
	      sed 's/NTPSOct94/NTPSOct95/g'
       This is particularly important for Windows NT 3.5 users.

AUTHOR

       fixnt   was   written   by   Holger   Bauer   <Holger.Bauer@topmail.de>,  Michael  Rath	<rath@itsm.uni-stuttgart.de>,  and  Akim  Demaille
       <demaille@inf.enst.fr>.

REPORTING BUGS

       Report bugs to the Authors, but avoid sending large postscript files.

       Patches are always welcome; send to <bauer@itsm.uni-stuttgart.de>.

SEE ALSO

       psnup(1), sed(1)

a2ps								   February 2003							  fixnt(1)
All times are GMT -4. The time now is 09:36 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy