Passing part of patterns from sed to shell

Question

I have a file which contains lines of the following format:

w1#1#x w2#4#b w3#2#d ...

Each word (token) in the line (e.g. w1#1#x) is made of 3 parts, the first showing some index (w1 in this case), the second is an integer (1 in this case) , and the third is a character (x in this case)

Now, for each word (token), I need to print an additional field which will be calculated based on value of second and third part (i.e., the 4th part will be a function of 2nd and 3rd part), and the output file should look like:

w1#1#x#f1 w2#4#b#f2 w3#2#d#f3 ...

where

f1 = function(1,x), f2 = function(4,b), f3 = function (2,d)

Now, using the sed patterns I can identify the components in every word (token), e.g.,

echo $line | sed "s/([^#])#([^#])#([^# ]*) /\1#\2#\3 /g"

where \2 and \3 are parts of the pattern (I am calling them parts of the pattern because of this link)

Now, I need to compute the 4th part using \2 and \3. I have defined a shell function getInfo() which takes 2 arguments and does the required computation and gives me back the 4th part. The problem is inserting this function in the sed command. I tried following:

echo $line | sed "s/([^#])#([^#])#([^# ]*) /\1#\2#\3`getInfo \2 \3` /g"

but this is not working. Shell is not receiving the parts of the pattern as arguments.

So the question is:

How to pass the sed parts of the pattern to a shell (function)?

I can easily write a shell script which would split the line word-by-word and do the required job and then stitch the file back, but I would really appreciate if shell can receive parts of the pattern as arguments from sed within the sed command.

Regards,

Salil Joshi

Answer 1

This might work for you:

func(){ echo "$1#$2#$3#$2$3"; }
export -f func
echo "w1#1#x w2#4#b w3#2#d" |
sed 's/\([^#]*\)#\([^#]*\)#\([^ ]*\) \?/echo -n "$(func \1 \2 \3) "; /g;s/$/echo ""/' |
sh
w1#1#x#1x w2#4#b#4b w3#2#d#2d 

Or if you have GNU sed:

func(){ echo "$1#$2#$3#$2$3"; }
export -f func
echo "w1#1#x w2#4#b w3#2#d" |
sed 's/\([^#]*\)#\([^#]*\)#\([^ ]*\) \?/echo -n "$(func \1 \2 \3) "; /ge;s/.$//'
w1#1#x#1x w2#4#b#4b w3#2#d#2d