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sed to replace at fixed location

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# 1  
Old 07-03-2011
sed to replace at fixed location
I have got a text file- each line of 200 characters length. The file is too large in size. It could be 100 MB. The lines begin with any of 0,1,2,3,4,5. I want to replace from 121-131 characters with spaces irrespective of wehatever it is there (the exisitng charatcers could be spaces). And this I want only for the lines starting with 3. Can someone help me how to proceed ?
Code:
1 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBC  CCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
0 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
3 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCC     CCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
3 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCCCCCCCC 6  CDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
5 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
1 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND

Afrer replacing it will look like
Code:
1 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBC  CCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
0 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
3 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBC          CCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
3 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBC            CDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
5 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND
1 THIS IS TO EXPLAIN WITH AN EXAMPLE HOW WE PROCESS THE STANDARD FLOW OF DATA SET     1 AAAAAAAAAAAAAAAAABBBBBBBBBBBBBBCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFfGGGGGGGHHHHEND

# 2  
Old 07-04-2011
why sed? For algorithms or logic awk's much better.

Code:
awk -v FS="" -v OFS="" '/^3 / { for(N=121; N<=131; N++) $N=" "; } 1' < datain > dataout

# 3  
Old 07-04-2011
Thank you very much for your quick response. I am not much comfortable with awk. I used this command but the dataout file appears to be identical. There is no error message either. What I could make out with my very basic knowledge is that it takes input and output field separator as nothing and matches lines starting with3 (^3) and reads chars from 121 to 131 and replaces with space. I could not make out the 1 just before '. Am I doing something wrong or does the command need to be updated ?
# 4  
Old 07-04-2011
Try this.
Code:
 
 
nawk '/^3/ { printf("%s",substr($0,1,120)); for (i=0;i<11;i++)printf(" ");print substr($0,132,length($0)) }' input

# 5  
Old 07-04-2011
Through Sed..
Code:
# Replace * with spaces
sed '/^3/s/\(.\{120\}\)\(.\{11\}\)\(.*\)$/\1*******\3/' inputfile

sed '/^3/s/./*****/121' inputfile # Works with GNU Sed

# 6  
Old 07-04-2011
Simple & quite generic :

Code:
sed '/^3/s/........../          /13' infile

Code:
awk '/^3/{sub(substr($0,121,10),"          ")}1' infile

Use nawk or /usr/xpg4/bin/awk instead of the simple 'awk' if running SunOS/Solaris plateform
Last edited by ctsgnb; 07-04-2011 at 04:41 AM..
This User Gave Thanks to ctsgnb For This Post:
asutoshch
# 7  
Old 07-04-2011
Thank you very much. The awk command works fine. I will try with the sed commands.
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