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Need help on find and replacement on specific line and position

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Top Forums Shell Programming and Scripting Need help on find and replacement on specific line and position
# 22  
Old 01-16-2014
Some example might help you to understand

Code:
# Replace 3rd char with star
$ echo "1234567890" | awk -F "" '{gsub(".","*",$3)}1' OFS=""
12*4567890

# Replace 5th char onwards with some string
$ echo "1234567890" | awk  '{$0=substr($0,1,5) New}1' New="tester"
12345tester

Read below one

substr(string, start, length)This returns a length-character-long substring of string, starting at character number start. The first character of a string is character number one.

Example:
substr("washington", 5, 3) returns "ing". If length is not present, this function returns the whole suffix of string that begins at character number start.

substr("washington", 5) returns "ington". This is also the case if length is greater than the number of characters remaining in the string, counting from character number start.
# 23  
Old 01-16-2014
Quote:
Originally Posted by Akshay Hegde
Some example might help you to understand

Code:
# Replace 3rd char with star
$ echo "1234567890" | awk -F "" '{gsub(".","*",$3)}1' OFS=""
12*4567890

# Replace 5th char onwards with some string
$ echo "1234567890" | awk  '{$0=substr($0,1,5) New}1' New="tester"
12345tester

... ... ...
Note that the standards say that the results are unspecified if an empty string is assigned to FS. Some versions of awk will produce the output you showed above in your first example. The version of awk on OS/X issues the warning and output:
Code:
awk: field separator FS is empty

1234567890

A better example might be:
Code:
echo "1234567890" | awk '{print substr($0,1,2)"*"substr($0,4)}'

which should produce the output:
Code:
12*4567890

with any version of awk that conforms to the standards.

And, in your 2nd example, the comment says you're replacing the 5th character, but the substr() is copying the 1st five characters unchanged.
This User Gave Thanks to Don Cragun For This Post:
Rajesh_us
# 24  
Old 01-17-2014
Don I don't know about the OS/X, and in second example I mean to say retain 1st five char and 5th char onwards to length of line replace with some string, Sorry for bad English
This User Gave Thanks to Akshay Hegde For This Post:
Rajesh_us
# 25  
Old 01-17-2014
Quote:
Originally Posted by Akshay Hegde
Don I don't know about the OS/X, and in second example I mean to say retain 1st five char and 5th char onwards to length of line replace with some string, Sorry for bad English
I'm not concerned about your English. You are much better at English than I am in your native language! (When I attended college, I was allowed to use proficiency in FORTRAN and CDC assembler to meet MSU's requirement to understand a foreign language.)

I only mentioned the -F "" issue because the O/S being used by the submitter of this thread was never specified. The code you gave will work fine with gawk (or awk on a Linux system), but it is not portable to other systems since the standards explicitly state that the results are unspecified in this case. (OS/X is just one example of a system where an empty string is not accepted by awk as a field separator.)
This User Gave Thanks to Don Cragun For This Post:
Rajesh_us
# 26  
Old 01-17-2014
@ Don

You are right as always ! I tested it on GNU Awk 3.1.7, without warnings it worked there.
This User Gave Thanks to Akshay Hegde For This Post:
Rajesh_us
# 27  
Old 01-29-2014
Quote:
Originally Posted by Don Cragun
So there were two off by one errors. Also change:
Code:
      for(i=1;i<length(F);i++)N[substr(F,i,1)]=substr(T,i,1);

to:
Code:
      for(i=1;i<=length(F);i++)N[substr(F,i,1)]=substr(T,i,1);

Code:
awk  -v k3="$k3" '
    BEGIN{
      F="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
      T="ZYXWVUTSRQPONMLKJIHGFEDCBAzyxwvutsrqponmlkjihgfedcba9876543210"
      for(i=1;i<=length(F);i++)N[substr(F,i,1)]=substr(T,i,1);
    }
    NR == k3 {
      out=x
      for(i=1;i<=length;i++) {
         c=substr($0,i,1)
         out=out (i>9&&(c in N)?N[c]:c)
      }
      $0=out
    }
    1
' $file

i don't have any issue with the above code. is it possible to make the above code work on single field .. say field $3 .. first it has to search a specific field ($3) . in field # 3, it has to replace from 9 th posotion to end of line
# 28  
Old 01-29-2014
This should match on field three, notice how if matching the "*" (star) character two backquotes are needed.

The star on the end is to match with the rest of the string so example is looking for any field 3 that starts with "NM1*IL*1"

Code:
k3='NM1\\*IL\\*1*'
awk -v k3="$k3" '
    BEGIN{
      F="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
      T="ZYXWVUTSRQPONMLKJIHGFEDCBAzyxwvutsrqponmlkjihgfedcba9876543210"
      for(i=1;i<=length(F);i++)N[substr(F,i,1)]=substr(T,i,1);
    }
    $3 ~ k3 {
      out=x
      for(i=1;i<=length($3);i++) {
         c=substr($3,i,1)
         out=out (i>9&&(c in N)?N[c]:c)
      }
      $3=out
    }
    1
' $file

This User Gave Thanks to Chubler_XL For This Post:
Rajesh_us
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