asked on

Replace the specific position in a file

Need to read the file each line and replace the specific position if first 2 position have specific value .

Inputfile before modification

58855kkdlfldfddkdkdkkdkdkdk
22testingperl
565gglrphdhdjjskkskllslseee
77testingcontext123read

Inputfile after modification

If position 1-2=22 replace position 10-13 with 'y'

If position 1-2=77 replace position 17-19 with 'x'

58855kkdlfldfddkdkdkkdkdkdk
22testingnyyy
565gglrphdhdjjskkskllslseee
77testingcontextxxxread

ozo

perl -i -pe 's/(?<=^22.{8}).../yyy/;s/(?<=^77.{14}).../xxx/' Inputfile

wilcoxon

I notice one problem with your example and ozo's code. You say if 22 then position 10-13 which is 4 characters (not 3) so the second line should be 22testingyyyy.

I assume you are using base-1 indexes (eg first character = 1) and not typical perl base-0 (eg first character = 0)?

If so, alternately:

perl -i -pe 'if (substr($_, 0, 2) eq "22") { substr($_,9,4) = "yyyy" } elsif (substr($_,0,2) eq "77") { substr($_,16,3) = "xxx" }'

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steve wa

ASKER

Thank you for correction in my example can I put the code inside .pl script and passing inputfile as parameter?
./Script.pl test.txt

Code provided $ argv [0]

ozo

#!/usr/bin/perl -i.bak -p
s/(?<=^22.{8}).../yyy/;s/(?<=^77.{14}).../xxx/ # modulo corrections in your example

steve wa

ASKER

I used the code provided by willcoxon.

Running like this.
Perl test.pl inputfile

Got the following error

do u need to predeclare pe?
String found where operator expected
Scalar found where operator expected

ASKER CERTIFIED SOLUTION

wilcoxon

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wilcoxon

My original answer was for a one-liner run from the command-line. You could do the minimal modifications (see below) indicated by ozo's answer or you could use the alternate script I provide above.

#!/usr/bin/perl -i -p
if (substr($_, 0, 2) eq "22") { substr($_,9,4) = "yyyy" } elsif (substr($_,0,2) eq "77") { substr($_,16,3) = "xxx" }

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steve wa

ASKER

Used the multi line codr using foreach

use of uninitialized value $ argv [1] in concatenation (·) or string at script.pl
Could not tie : no such file or directoru at script.pl

wilcoxon

Oops. The places that have $ARGV[1] should be $ARGV[0] ($0 = program name but $ARGV[0] = first argument passed in).

steve wa

ASKER

Getting help very quickly.I thought i accepted solution .Sorry for the delay.