egrep uses EREs (Extended Regular Expressions) From POSIX.2
Quote:
An atom followed by `*' matches a sequence of 0 or more matches of the atom. An atom followed by `+' matches a sequence of 1 or more matches of the atom. An atom followed by `?' matches a sequence of 0 or 1 matches of the atom.
Thus "a?" implies 0 or 1 matches of "a" and "a*" implies 0 or more matches of "a".
If you want to just list the lines containing a, the following will work
Thus "a?" implies 0 or 1 matches of "a" and "a*" implies 0 or more matches of "a".
That's what i am asking. I know "a?" means 0 or 1 occurrence of preceding pattern. I was thinking it as exactly 0 or 1 occurrence. but it's not like that. I am not getting the difference between "*" and "?" . If there is any can you give me some example of it.
Remember that you are doing a grep. That means the command will list down lines from the file that match the input pattern.
In this case egrep works on your patterns a? and a* in the following way.
egrep a? --> List down lines from test.txt if it contains an a followed by any character. Which means a, aa, abcdef, a897 all will match, and hence you get all these in the output.
egrep a* --> List down lines from test.txt if it contains an a followed by 0 or more nr of characters. Again a, aa, abcdef, a897 all will match.
Hope you get the point.
Moreover, to see the difference between ? and *, create files with names : a, aa, a897, abcd
and then do
and
Hi 2 all,
i have had AIX 7.2
:/# /usr/IBMAHS/bin/apachectl -v
Server version: Apache/2.4.12 (Unix)
Server built: May 25 2015 04:58:27
:/#:/# /usr/IBMAHS/bin/apachectl -M
Loaded Modules:
core_module (static)
so_module (static)
http_module (static)
mpm_worker_module (static)
... (3 Replies)
Hello.
System : opensuse leap 42.3
I have a bash script that build a text file.
I would like the last command doing :
print_cmd -o page-left=43 -o page-right=22 -o page-top=28 -o page-bottom=43 -o font=LatinModernMono12:regular:9 some_file.txt
where :
print_cmd ::= some printing... (1 Reply)
How to use "mailx" command to do e-mail reading the input file containing email address, where column 1 has name and column 2 containing “To” e-mail address
and column 3 contains “cc” e-mail address to include with same email.
Sample input file, email.txt
Below is an sample code where... (2 Replies)
The system don't boot.
on the screen appears following:
press enter to maintenance (or type CTRL-D to continue)...I checked with format command.
... the slices "0-root","1-swap","2-backup" exist.
...the slises "3-var","6-usr" -unassigned. :( (16 Replies)
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)
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)
Hi,
could someone pls enlighten me on the difference between the "root" package and "usr" package?
Like in this example:
pkginfo -l SUNWGtku | grep -i desc
DESC: GTK - The GIMP Toolkit (Usr)
and
pkginfo -l SUNWGtkr | grep -i desc
DESC: GTK - The GIMP Toolkit (Root)... (6 Replies)
Hi Friends,
Can any of you explain me about the below line of code?
mn_code=`env|grep "..mn"|awk -F"=" '{print $2}'`
Im not able to understand, what exactly it is doing :confused:
Any help would be useful for me.
Lokesha (4 Replies)