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Replace a particular pattern in a file

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# 1  
Old 11-24-2010
Replace a particular pattern in a file
Hi ,
I have a requirement where i have this file

abcd
$$xyz=123
$$zef=789

$$mno=123
$$pqr=456

I need to replace $$pqr from 456 to a new value which will be present in a variable to me.
I am not aware of sed and awk functionality.
Can somebody please show me how to replace this 456 with a new value .
# 2  
Old 11-24-2010
perl -e -pi s/456/'$var'/g infile
# 3  
Old 11-24-2010
If pqr can have any numeric value you can use:

Code:
sed 's/\(^$$pqr=\)[0-9][0-9]*$/\1'"$VAR"'/' infile

# 4  
Old 11-24-2010
alternative in sed..
Code:
sed '/$$pqr/s/[0-9]\+/'$VAR'/' inputfile > outfile

# 5  
Old 11-24-2010
And another one with awk:
Code:
awk -v var=$variable -F= '/\$\$pqr/{$2=var}1' OFS=\= infile

# 6  
Old 11-24-2010
Code:
sed '/$$pqr=/'"s/=.*/=$var/" infile

Code:
sed "/\$\$pqr=/s/=.*/=$var/" infile

# 7  
Old 11-24-2010
Or using Perl -

Code:
$
$ cat f42
abcd
$$xyz=123
$$zef=789
 
$$mno=123
$$pqr=456
$
$
$ typeset -x VAR="999"
$
$ # Perl one-liner to substitute the value
$ perl -lne 'if (/^(\$\$pqr=).*/){print $1,$ENV{"VAR"}} else {print}' f42
abcd
$$xyz=123
$$zef=789
 
$$mno=123
$$pqr=999
$
$

tyler_durden
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