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I would like to replace "CC" with "C" and "AA" with A" in a particular column of Tab delimited file (using awk probably).

  • My input data file abc.txt has this "20131008","0004","0568","98" I ran this command to replace the text nawk -F, -vOFS=',' '{gsub("0568","0808",$3); print }' abc.txt In the output the delimiter "," is replaced with a space. The output looks like this "20131008" "0004" "0568" "98". Can someone please help with this? I tried to replace the -vOFS but doesnt work. – user3213938 Aug 19 '14 at 1:14
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awk -F'\t' -vOFS='\t' '{ gsub("CC", "C", $1) ; gsub("AA", "A", $1) ; print }'

Replace $1 with the column that you wish to modify.

  • In case the delimiter has to be kept, a -vOFS='\t' option may be added. – manatwork Jun 14 '12 at 10:18
  • @manatwork Good point, added. – Chris Down Jun 14 '12 at 10:20
  • fantastic! works as per usual!!! – alex Jun 14 '12 at 10:51
  • Some versions of awk don't have a gsub function. How would you do it then? Can sed be used instead? – rahmu Jun 14 '12 at 13:33
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    @rahmu - gsub() has been defined by POSIX for over 20 years, so my suggestion would be to get a version of awk that isn't downright awful ;-) – Chris Down Jun 14 '12 at 13:40
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If you didn't have access to gsub(), but you do have access to split(), you could just create the equivalent thusly:

Given the input

AA      AA      CC      CC      AA      CC

the following awk script

BEGIN {
    OFS = "\t";
    split("1 3 5", Fields);
    split("A C", Replacements);
}
{
    for (i in Fields) {
        for (j in Replacements) {
            Replace = Replacements[j];
            sub(Replace Replace, Replace, $Fields[i]);
        }
    }
    print;
}

would produce the desired results for fields 1, 3, and 5:

A       AA      C       CC      A       CC

Even without split() it's possible if you want to hard-code the Fields and Replacements arrays in the BEGIN block.

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To find and replace in one field use this command:

sed 's/whatyouwanttofind/whatyouwanttoreplace/field#'

i.e. you echo this:

$echo -e "1are,2are,3are,4are\n5are,6are,7are,8are"

1are,2are,3are,4are

5are,6are,7are,8are

and you want to do this

$echo -e "1are,2are,3are,4are\n5are,6are,7are,8are" |  sed 's/are/arrr/2'

1are,2**arrr**,3are,4are

5are,6**arrr**,7are,8are

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