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awk and gsub - how to replace only the first X occurrences

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# 1  
Old 09-24-2010
awk and gsub - how to replace only the first X occurrences
I have a text (text.txt) and I would like to replace only the first 2 occurrences of a word (but I might need to replace more):

For example, if text is this:

Code:
CAR sweet head
hat red yellow
CAR book brown
tiger CAR cow CAR
CAR milk

I would like to replace the word "CAR" with word "REPLACE" only in row 1 and 3 but not in row 4 and 5 and I would like to obtain a result like this:

Code:
REPLACE sweet head
hat red yellow
REPLACE book brown
tiger CAR cow CAR
CAR milk

but if I use:

Code:
cat text.txt | awk '{gsub("CAR","REPLACE");print}'

I will obtain this:

Code:
REPLACE sweet head
hat red yellow
REPLACE book brown
tiger REPLACE cow REPLACE
REPLACE milk

Is there a way to obtain what i need (if possible using awk and gsub)?

Thanks in advance.
# 2  
Old 09-24-2010
Code:
$ ruby -00 -ne 'print $_.split("CAR",3).join("REPLACE")' file
REPLACE sweet head
hat red yellow
REPLACE book brown
tiger CAR cow CAR
CAR milk

# 3  
Old 09-24-2010
Code:
cat text.txt |
awk '/CAR/{
  if ( count < 2 ){ gsub("CAR","REPLACE")}
  count++
  print
  }'

...oh... and you can pass in the 2 as a variable:

Code:
cat text.txt |
awk '/CAR/{
  if ( count < counter ){ gsub("CAR","REPLACE")}
  count++
  print
  }' counter=$counter

# 4  
Old 09-24-2010
Thanks, but using awk and gsub?

I don't know ruby and I would like to use awk because so I could adapt the script to my needs.

Thanks again

---------- Post updated at 04:44 PM ---------- Previous update was at 04:43 PM ----------

Thanks again, I had not seen the last message

---------- Post updated at 04:55 PM ---------- Previous update was at 04:44 PM ----------

@quirkasaurus

I have tested your first code but I obtain this output:

Code:
REPLACE sweet head
REPLACE book brown
tiger CAR cow CAR
CAR milk

The second row is deleted

---------- Post updated at 04:59 PM ---------- Previous update was at 04:55 PM ----------

With this code it runs:

Code:
cat text.txt | awk '{if ( count < 3 ){ gsub("CAR","REPLACE")} count++; print}'

# 5  
Old 09-24-2010
oops. sorry. didn't notice that.

Code:
cat text.txt |
awk '{
  if ( count < 2 ){
    gsub("CAR","REPLACE")
    count++
    }
  print
  }'

Code:
output:
REPLACE sweet head
hat red yellow
CAR book brown
tiger CAR cow CAR
CAR milk

# 6  
Old 09-24-2010
I need a code like this because, since I have a big file where to search, I would like to stop search at first 2 occurrences found but with gsub I think search is done until the end of file, instead with this code (using sub in place of gsub):

Code:
cat text.txt | awk '{sub("CAR","REPLACE");print}'

search is done until awk find the occurence. Is it right?
# 7  
Old 09-24-2010
quirkasaurus,
your code is not replacing 2nd occurance.

slightly change in your code
Code:
awk '/CAR/ && count < 2  {gsub("CAR","REPLACE");count++} {print $0}' infile
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