gsub issue with awk (gawk) - windows

Question

I need to search a text file for a string, and make a replacement that includes a number that increments with each match.
The string to be "found" could be a single character, or a word, or a phrase.
The replacement expression will not always be the same (as it is in my examples below), but will always include a number (variable) that increments.
For example:
1) I have a test file named "data.txt". The file contains:
Now is the time
for all good men
to come to the
aid of their party.
2) I placed the awk script in a file named "cmd.awk". The file contains:
/f/ {sub ("f","f(" ++j ")")}1
3) I use awk like this:
awk -f cmd.awk data.txt
In this case, the output is as expected:
Now is the time
f(1)or all good men
to come to the
aid of(2) their party.
The problem comes when there is more than one match on a line. For example, if I was searching for the letter "i" like:
/i/ {sub ("i","i(" ++j ")")}1
The output is:
Now i(1)s the time
for all good men
to come to the
ai(2)d of their party.
which is wrong because it doesn't include the "i" in "time" or "their".
So, I tried "gsub" instead of "sub" like:
/i/ {gsub ("i","i(" ++j ")")}1
The output is:
Now i(1)s the ti(1)me
for all good men
to come to the
ai(2)d of thei(2)r party.
Now it makes the replacement for all occurrences of the letter "i", but the inserted number is the same for all matches on the same line.
The desired output should be:
Now i(1)s the ti(2)me
for all good men
to come to the
ai(3)d of thei(4)r party.
Note: The number won't always begin with "1" so I might use awk like this:
awk -f cmd.awk -v j=26 data.txt
To get the output:
Now i(27)s the ti(28)me
for all good men
to come to the
ai(29)d of thei(30)r party.
And just to be clear, the number in the replacement will not always be inside parenthesis. And the replacement will not always include the matched string (actually it would be quite rare).
The other problem I am having with this is...
I want to use an awk-variable (not environment variable) for the "search string", so I can specify it on the awk command line.
For example:
1) I placed the awk script in a file named "cmd.awk". The file contains something like:
/??a??/ {gsub (a,a "(" ++j ")")}1
2) I would use awk like this:
awk -f cmd.awk -v a=i data.txt
To get the output:
Now i(1)s the ti(2)me
for all good men
to come to the
ai(3)d of thei(4)r party.
The question here, is how do I represent the the variable "a" in the /search/ expression ?

Answer 1

awk version:
awk '{for(i=2; i<=NF; i++)$i="(" ++k ")" $i}1' FS=i OFS=i

Answer 2

gensub() sounds ideal here, it allows you to replace the Nth match, so what sounds like a solution is to iterate over the string in a do{}while() loop replacing one match at a time and incrementing j. This simple gensub() approach won't work if the replacement does not contain the original text (or worse, contains it multiple times), see below.
So in awk, lacking perl's "s///e" evaluation feature, and its stateful regex /g modifier (as used by Steve) the best remaining option is to break the lines into chunks (head, match, tail) and stick them back together again:
BEGIN {
if (j=="") j=1
if (a=="") a="f"
}
match($0,a) {
str=$0; newstr=""
do {
newstr=newstr substr(str,1,RSTART-1) # head
mm=substr(str,RSTART,RLENGTH) # extract match
sub(a,a"("j++")",mm) # replace
newstr=newstr mm
str=substr(str,RSTART+RLENGTH) # tail
} while (match(str,a))
$0=newstr str
}
{print}
This uses match() as an epxression instead of a // pattern so you can use a variable. (You can also just use "($0 ~ a) { ... }", but the results of match() are used in this code, so don't try that here.)
You can define j and a on the command line.
gawk supports \y which is the equivalent of perlre's \b, and also supports \< and \> to explictly match the start and end of a word, just take care to add extra escapes from a unix command line (I'm not quite sure what Windows might require or permit).
Limited gensub() version
As referenced above:
match($0,a) {
idx=1; str=$0
do {
prev=str
str=gensub(a,a"(" j ")",idx++,prev)
} while (str!=prev && j++)
$0=str
}
The problems here are:
if you replace substring "i" with substring "k" or "k(1)" then the gensub() index for the next match will be off by 1. You could work around this if you either know that in advance, or work backward through the string instead.
if you replace substring "i" with substring "ii" or "ii(i)" then a similar problem arises (resulting in an infinite loop, because gensub() keeps finding a new match)
Dealing with both conditions robustly is not worth the code.

Answer 3

I'm not saying this can't be done using awk, but I would strongly suggest moving to a more powerful language. Use perl instead.
To include a count of the letter i beginning at 26, try:
perl -spe 's:i:$&."(".++$x.")":ge' -- -x=26 data.txt
This could also be a shell var:
var=26
perl -spe 's:i:$&."(".++$x.")":ge' -- -x=$var data.txt
Results:
Now i(27)s the ti(28)me
for all good men
to come to the
ai(29)d of thei(30)r party.
To include a count of specific words, add word boundaries (i.e. \b) around the words, try:
perl -spe 's:\bthe\b:$&."(".++$x.")":ge' -- -x=5 data.txt
Results:
Now is the(6) time
for all good men
to come to the(7)
aid of their party.