search and replace string occurance in a specific column

[jabir m]

Hi -

I am trying to write a code to search and replace the occurrence of a string in a specific column.

Can any one please help me to do this?

i/p

20120311~0568~12~ 12.34~231.45     

20120311~0808~12~ 11.34~568.45 

20120312~0568~12~ 10.34~161.45     

o/p required

20120311~0808~12~ 12.34~231.45     

20120311~0808~12~ 11.34~568.45

20120312~0808~12~ 10.34~161.45    

in the above example, i need to replace 568 to 808 in the second column.

I tried with sed and it is replacing 568 in all place.

thanks

Jabir

[jabir m]

the data is in a file and I am trying to do with shell scripting in Unix environment

[jabir m]

I found a solution by searching net and here is what i did

nawk -F'~'  '{gsub("568","808",$2)}1' filename

On Thursday, September 4, 2014 9:57:19 AM UTC-7, jabir m wrote:

[Marek Borowiec]

Awk certainly is more elegant, but depending on how stable the patterns in your file are, you could still use sed with regular expressions:

sed  -i 's/\(^[0-9]\+~\)[0-9]\+/\10808/g' <filename>

This would take your file, store first column (pattern of multiple numbers) from the beginning of line (^) plus the delimiter (~) into the first backreference, then find immediately following pattern of numbers and substitute those with your first column, or backreference \1, followed by 0808. Note the backslashes that denote non-literal interpretation of special characters for regex (plus signs and parentheses). This results in:

20120311~0808~12~ 12.34~231.45     

20120311~0808~12~ 11.34~568.45 

20120312~0808~12~ 10.34~161.45

Best,

Marek

 

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Marek L. Borowiec
Ward Lab, 381 Briggs Hall
Department of Entomology
University of California, Davis
One Shields Avenue
Davis, CA 95616

https://sites.google.com/site/marekborowiecmyrmecologist/