Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: how to use regular expression in Bash Shell Scripting
Top Forums Shell Programming and Scripting how to use regular expression in Bash Shell Scripting Post 302175053 by vino on Thursday 13th of March 2008 12:09:01 AM
Old 03-13-2008
Quote:
Originally Posted by sunitachoudhury
Hi,

Actually i have written one test.sh (shell program) in bash.

Here i have a variables $a which stored the value package1.

Now I want to write a regular expression inside the if command that "if $a variable contains letter p in the begining of the value package1 then it is coming true. else it is coming false". For this i have written the following shell script.

a=package1
if grep "^p" $a
then
echo "true"
else
echo "false"
fi
echo "hello jim" | sed -e 's/hello/bye/'

But when i am running the following test.sh then i am getting the following error.

grep: can't open package1
false
bye jim

can anybody help me please to rectify this problem. Please help me. It is very urgent.
Grep expects a file name. In your case, package1 is not a file and hence the grep error.

You should rather do it as

Code:
echo $a | grep "^p"
if [[ $? -eq 0 ]] ; then
..
..
..

Last edited by vino; 03-13-2008 at 02:10 AM.. Reason: Typo
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

using regular expression an shell script!!

I want to check if the first argument of my shell script starts with a specifiec string? Any Idea?? Thank u (3 Replies)
Discussion started by: andy2000
3 Replies

2. Shell Programming and Scripting

Regular expression matching in BASH (equivalent of =~ in Perl)

In Perl I can write a condition that evaluates a match expression like this: if ($foo =~ /^bar/) { do blah blah blah } How do I write this in shell? What I need to know is what operator do I use? The '=~' doesn't seem to fit. I've tried different operators, I browsed the man page for... (3 Replies)
Discussion started by: indiana_tas
3 Replies

3. Shell Programming and Scripting

problem with Regular expression as input in shell script

Hi, I have script which will take a string as input and search in a file. But when I want to search a pattern which has special characters script is ignoring it. For example: I want to search a pattern "\.tumblr\.com". shell script is removing \ (backslah) and trying to search... (7 Replies)
Discussion started by: Anjan1
7 Replies

4. Shell Programming and Scripting

Need help in Regular expression in bash shell

hi, I have written a script to search MAC address in a given directory. MAC address would be in format XX.XX.XX.XX. The digits contain hexadecimal numbers. For this i have used grep as follows. grep -rn '^\{1,2\}\.\{1,2\}\.\{1,2\}\.\{1,2\}\$' * This is not working as required.... (17 Replies)
Discussion started by: flamingo_l
17 Replies

5. Shell Programming and Scripting

search a regular expression and match in two (or more files) using bash

Dear all, I have a specific problem that I don't quite understand how to solve. I have two files, both of the same format: XXXXXX_FIND1 bla bla bla bla bla bla bla bla bla bla bla bla ======== (return) XXXXXX_FIND2 bla bla bla bla bla bla (10 Replies)
Discussion started by: TheTransporter
10 Replies

6. Programming

Perl: How to read from a file, do regular expression and then replace the found regular expression

Hi all, How am I read a file, find the match regular expression and overwrite to the same files. open DESTINATION_FILE, "<tmptravl.dat" or die "tmptravl.dat"; open NEW_DESTINATION_FILE, ">new_tmptravl.dat" or die "new_tmptravl.dat"; while (<DESTINATION_FILE>) { # print... (1 Reply)
Discussion started by: jessy83
1 Replies

7. Shell Programming and Scripting

regular expression with shell script to extract data out of a text file

hi i am trying to extract some specific data out of a text file using regular expressions with shell script that is using a multiline grep .. and the tool i am using is pcregrep so that i can get compatibility with perl's regular expressions for a sample data like this, i am trying to grab... (6 Replies)
Discussion started by: vemkiran
6 Replies

8. Shell Programming and Scripting

incorporating a regular expression statement in a shell script (.sh)

I do have a shell file where I call many unix commands . I would like to add a regular expression step in that shell file, where a text file, say Test.txt has to be openned and all the :'s should be replaced. Basically apply the follwoing regular expression: :%s/://g to that particular text... (2 Replies)
Discussion started by: Lucky Ali
2 Replies

9. Shell Programming and Scripting

Hi im new to bash scripting I want to know what does the regex expression do ??

# check host value regex='^(||1|2|25)(\.(||1|2|25)){3}$' if ')" != "" ]; then if ]; then echo host $host not found exit 4 fi elif ]; then echo $host is an invalid host address exit 5 fi (1 Reply)
Discussion started by: kevin298
1 Replies

10. UNIX for Beginners Questions & Answers

SHELL: UNIX : Ls regular expression not working when used with variables

If i do below command in unix prompt which static values (ie 27..97), it is working fine and gives desired output >ls -d $WORKDIR/batch/somefilename_{27..97}.* 2>/dev/null somefilename_27.sometxt somefilename_28.sometxt somefilename_29.sometxt .. somefilename_97.sometxt But if i want... (2 Replies)
Discussion started by: haiderali
2 Replies

LEARN ABOUT BSD

re_comp

REGEX(3)						     Library Functions Manual							  REGEX(3)

NAME

       re_comp, re_exec - regular expression handler

SYNOPSIS

       char *re_comp(s)
       char *s;

       re_exec(s)
       char *s;

DESCRIPTION

       Re_comp	compiles a string into an internal form suitable for pattern matching.	Re_exec checks the argument string against the last string
       passed to re_comp.

       Re_comp returns 0 if the string s was compiled successfully; otherwise a string containing an error message  is	returned.  If  re_comp	is
       passed 0 or a null string, it returns without changing the currently compiled regular expression.

       Re_exec returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled regular
       expression, and -1 if the compiled regular expression was invalid (indicating an internal error).

       The strings passed to both re_comp and re_exec may have trailing or embedded newline characters; they are terminated by nulls.  The regular
       expressions recognized are described in the manual entry for ed(1), given the above difference.

SEE ALSO

       ed(1), ex(1), egrep(1), fgrep(1), grep(1)

DIAGNOSTICS

       Re_exec returns -1 for an internal error.

       Re_comp returns one of the following strings if an error occurs:

	    No previous regular expression,
	    Regular expression too long,
	    unmatched (,
	    missing ],
	    too many () pairs,
	    unmatched ).

3rd Berkeley Distribution					   May 15, 1985 							  REGEX(3)
All times are GMT -4. The time now is 03:14 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy