Visit Our UNIX and Linux User Community


Grep using wild card issue


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Grep using wild card issue
# 1  
Old 05-20-2010
Error Grep using wild card issue

Hi,

I am having a file (file1) having following contents

" xet B - All Divers/All Rivers - - ns - "

Now when i use

Code:
 cat file1 | grep 'RF'

it doesn't returns anything.
But on using
Code:
 cat file1 | grep 'RF*'

shows me this complete line

But in this file there is no word RF, then why grep is showing me this complete line on using RF*.

Thanks
Sarbjit
# 2  
Old 05-20-2010
From the man page of grep:
Quote:
Repetition
A regular expression may be followed by one of several repetition operators:
? The preceding item is optional and matched at most once.
* The preceding item will be matched zero or more times.
+ The preceding item will be matched one or more times.
{n} The preceding item is matched exactly n times.
{n,} The preceding item is matched n or more times.
{,m} The preceding item is matched at most m times.
{n,m} The preceding item is matched at least n times, but not more than m times.
So
Code:
grep 'RF*'

means "search for an uppercase R, followed by 0 or more uppercase F", which matches the 'R' in 'Rivers'.
# 3  
Old 05-20-2010
Because a * stands for "none or any number of the previous character". So a simple "R" in your input is a match.

When using grep, you don't need to pipe input via cut. Just do
Code:
grep RF* file1

# 4  
Old 05-20-2010
Also in this case "*" is not a wildcard, it's a modifier.
# 5  
Old 05-20-2010
Also, In regular expression terms, it is called as quantifiers.
"?" and "+" are the other two.
# 6  
Old 05-20-2010
Quote:
Originally Posted by anchal_khare
"?" and "+" are the other two.
Yes, but as far as I know "?" and "+" are not supported in BRE (grep's default).
# 7  
Old 05-20-2010
Quote:
Originally Posted by verdepollo
Yes, but as far as I know "?" and "+" are not supported in BRE (grep's default).
True for grep.

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Wild card for dir path

I have dir structure like this : /opt/oracle/product/abc/sqlplus/admin/ /opt/oracle/product/def/sqlplus/admin /opt/oracle/product/ghi/sqlplus/admin I am trying to use wildcard ( for dirs abc,def,ghi) ..something like this : cp xyz.txt ... (1 Reply)
Discussion started by: talashil
1 Replies

2. Shell Programming and Scripting

find with wild card [solved]

Can somebody help me with the following syntax? I want to find all files that end with *.arc SUFFIX=".arc" find /tmp -name "\*$SUFFIX" -print 2>/dev/null ---------- Post updated at 03:45 PM ---------- Previous update was at 03:41 PM ---------- got it thanks -name... (0 Replies)
Discussion started by: BeefStu
0 Replies

3. Shell Programming and Scripting

Passing variable and wild card character to grep in Perl

HI All, I have a script that needs to find out a list of files in a directory, i pass the search parameter as an argument. opendir ( DIR, $dir ) || die "Error in opening dir $dirname\n"; @filename1 = (grep {/$File_pattern/ } readdir(DIR)); The problem is my file patterns are like... (1 Reply)
Discussion started by: amit1_x
1 Replies

4. Shell Programming and Scripting

How to send a string to function containing wild card?

Hey All, I am trying to send a string as an input parameter to a function which contains a wild card character - * However the function is taking it as: PS: The directory - '/path/to/my/dir/' has 3 files: file1.out, file2.out, file3.out However I want to disable this wild... (2 Replies)
Discussion started by: paragkalra
2 Replies

5. Shell Programming and Scripting

wild card in if condition not working

Hi, I am using RHEL5. I have following if condition. if In the above condition, if the value of a contains word WARNING, it should match. i.e., WARNING_MESSAGE, CRITICAL WARNING, WARNING ALERT etc. it should match. For b, alert error, ALERT ERROR, ERROR IMMEDIATE ACTION REQUIRED, etc... (2 Replies)
Discussion started by: user7509
2 Replies

6. AIX

df, grep, wild card

Hi, I want to monitor my filesystem capacity and I want to df with grep wildcard for all 9*%. Is this possible? I want to replaced all the existing complicated scripts I have in the system. Thanks, Itik (2 Replies)
Discussion started by: itik
2 Replies

7. Shell Programming and Scripting

Wild card in find perm

Hi, Is there a way to use find command to list the directories for certain permissions. I know we can use find . -type d -perm nnn, where nnn is the permission number . However I wold like to know if I wanna search for wild card permissions i.e 75* / 7* / 55* , as i do not know the actual... (1 Reply)
Discussion started by: braindrain
1 Replies

8. UNIX for Dummies Questions & Answers

How do I pass a wild card as an argument

Hi, I would like to pass a wild card as part of an argument. But when I do it the script views the wild card as text. Example: sFile=MG1A* sort $sFile > $sFile.sorted What I get is MG1A*.sorted The problem is I am passed a series of files where the first few characters like "MG1A"... (2 Replies)
Discussion started by: eja
2 Replies

9. UNIX for Dummies Questions & Answers

ls and wild card - Should be simple!

I am trying to cp files that have F0 as prefix in their name in path p1/p2 to path p3/p4 this command does not work - Why? (I am using HP/UX) cp p1/p2/F0* p3/p4 thanks. (2 Replies)
Discussion started by: GNMIKE
2 Replies

10. UNIX for Dummies Questions & Answers

using if with wild card patterns

Hi, Please help me. Suppose I have a file which contains files like: My file :/tmp/rooh_20020518.lst it consists: ASI00320225041925URD01 ASI00320225041925KER02 ASI00390228095244KER08 ... (1 Reply)
Discussion started by: rooh
1 Replies

Featured Tech Videos