How to replace characters 7 through 14 of every line in a file - Shell Programming and Scripting

jakSun8 · #1 12-12-2007

Hi all,

I have a file with multiple lines. I want to replace characters 7 through 14 of every line with 0000000

Input:
12345678901234567890
23456789012345678901

Output
12345600000004567890
23456700000005678901

Please help.

JaK

rikxik · #2 12-12-2007

awk '{print substr($0,1,6)"0000000"substr($0,14,10)}' infile

jakSun8 · #3 12-12-2007

Thanks rikxik, it works but when i run the same command on record which has lenght of 6656 bytes .. it says "record too long" .. is there some limitation on awk? How do i get around it?

Please help
JaK

ghostdog74 · #4 12-12-2007

in bash

Code:

# while read line; do echo ${line//${line:7:7}/0000000}; done < file

or

Code:

# for line in `cat file`; do echo ${line//${line:7:7}/0000000}; done

bakunin · #5 12-12-2007

sed 's/$.\{7\}$.\{7\}/\10000000/' oldfile > newfile

A lot faster than calling substr() two times in awk.

If your lines are too long to handle you could cut them before making the exchange and then put them together again:

Code:

typeset line=""
typeset start=""
typeset end=""

cat oldfile | while read line ; do
     start="(print - "$line" | cut -c1-14)"
     end="$(print - "$line" | cut -c15-)"
     start="${start%%???????}0000000"
     print - "${start}${end}" >> newfile
done

bakunin

jakSun8 · #6 12-12-2007

Thanks guys. To get around "too long" issue, I just used nawk instead and it worked.

Great to see people helping others!
JaK

rikxik · #7 12-12-2007

Consider this:

Quote:

$ head bigfile ; wc -l bigfile
12345678901234567890
23456789012345678901
12345678901234567890
23456789012345678901
12345678901234567890
23456789012345678901
12345678901234567890
23456789012345678901
12345678901234567890
23456789012345678901
20000 bigfile

@bakunin

sed definitely takes the cake (as long as no too long line issues):

Quote:

[sdass@db012a:PNB] /shared/home/sdass/tmp > time sed 's/$.\{7\}$.\{7\}/\10000000/' bigfile > newfile.sed

real 0m0.08s
user 0m0.03s
sys 0m0.00s

But wrongly produces lines like this - nothing which cannot be fixed:

Quote:

12345670000000567890
23456780000000678901

Instead of this:

Quote:

12345600000004567890
23456700000005678901

However, speaking of speed, the bash script you posted is as fast as a Snail:

Quote:

$ cat baku
#!/usr/bin/ksh

typeset line=""
typeset start=""
typeset end=""

cat bigfile | while read line ; do
start="(print - "$line" | cut -c1-14)"
end="$(print - "$line" | cut -c15-)"
start="${start%%???????}0000000"
print - "${start}${end}" >> newfile
done
$ time baku

real 5m6.62s
user 0m14.95s
sys 1m9.19s

And it produced incorrect output too.

@ghostdog74
This wasn't very fast either:

Quote:

$ cat ghost
#!/usr/bin/bash

while read line; do echo ${line//${line:7:7}/0000000}; done < bigfile > newfile.bash
$ time ghost

real 0m1.31s
user 0m0.82s
sys 0m0.44s

Mine wasn't too bad - not as fast as the sed version:

Quote:

$ time awk '{print substr($0,1,6)"0000000"substr($0,14)}' bigfile > newfile.awk

real 0m0.17s
user 0m0.11s
sys 0m0.00s

Nothing against anyone - just fair comparison.

HTH

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