nixCraft

I know how to get a filed, ie "echo aa,bb,cc | cut -f2 -d,"

BUt I do not know how to SET a field

How do I easily and efficiently SET the 4th field in a stirng

ex How to I put the value "HERE" into the string "one,two,three,four,five,six,seven,eight,nine, ten" ?

Which command should I use and how do I do this ?

Thanks, in advance, Gideon

Try:
$output stores value for 2nd field.

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Vivek Gite
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Thanks, but I think I was not clear in my post

I am trying to set the 4th field within a comma deliminted string:

If I have the following line:

aa,bb,cc,dd,ee,ff,gg,hh,ii,jj,kk

I want to place the value 'text' into the fourth field, as follows:

aa,bb,cc,text,ee,ff,gg,hh,ii,jj,kk

How can I do this ? Is there a paraleel command to cut ?

Thanks, Gideon

Use sed to match first occurrence of 4th field called dd and replace with 'text':
To find all occurrence of dd and replace with 'text':

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Vivek Gite
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That is helpful, but unfortunately, I need this for a record with variable data, so I can not guarantee that the fourth field will actually be the first occurence of 'dd'.. Its possible I could have a record that looks like:

aa,dd,dd,dd,ee,ff,gg,hh,ii,jj,kk

Is there any way to set the fourth field.

How would you normally handle this in Korn Shell ?

Thanks, Gideon

Bash / csh / ksh cannnot modify string. You need to use awk or sed or perl. Here is awk example to modify only 4th field,
Replaces only 4th instance of dd:
All examples are tested on GNU awk (gawk).

HTH

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Vivek Gite
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It can be done entirely in the shell with this function:

Code:

function repfield #@ Replace field in comma-separated string
{                 #@ USAGE: repfield string field replacement
  [ $# -ne 3 ] && return 1
  typeset string=$1 field=$2 replacement=$3 IFS=, x
  set -f
  x=( $string )
  set +f
  IFS=$' \t\n'
  x[field-1]=$replacement
  string=$(printf "%s," "${x[@]}")
  string=${string%,}
  printf "%s\n" "$string"
}

Wow! nicely done.

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Vivek Gite
Linux Evangelist
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Thanks, I really like that awk command

Just one thing. I tried this line:

echo 'aa,dd,dd,dd,ee,ff,gg,hh,ii,jj,kk' | awk -F',' '{$4="text"; print}'
and it returns the following output:

aa dd dd text ee ff gg hh ii jj kk

How can I put the comma's back into the rec ?

Thanks, Gideon