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POPassing part of patterns from sed to shell
 

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    <p>I have a file which contains lines of the following format:</p> <blockquote> <p>w1#1#x w2#4#b w3#2#d ...</p> </blockquote> <p>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)</p> <p>Now, for each word (token), I need to print an additional field which will be calculated based on value of second and third part (<em>i.e.</em>, the 4th part will be a function of 2nd and 3rd part), and the output file should look like:</p> <blockquote> <p>w1#1#x#f1 w2#4#b#f2 w3#2#d#f3 ...</p> </blockquote> <p>where</p> <blockquote> <p>f1 = function(1,x), f2 = function(4,b), f3 = function (2,d)</p> </blockquote> <p>Now, using the sed patterns I can identify the components in every word (token), <em>e.g.,</em></p> <blockquote> <p>echo $line | sed "s/([^#]<em>)#([^#]</em>)#([^# ]*) /\1#\2#\3 /g"</p> </blockquote> <p>where \2 and \3 are <em>parts of the pattern</em> (I am calling them <em>parts of the pattern</em> because of <a href="http://www.grymoire.com/Unix/Sed.html#uh-4" rel="noreferrer">this link</a>)</p> <p>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:</p> <blockquote> <p>echo $line | sed "s/([^#]<em>)#([^#]</em>)#([^# ]*) /\1#\2#\3`getInfo \2 \3` /g"</p> </blockquote> <p>but this is not working. Shell is not receiving the <em>parts of the pattern</em> as arguments.</p> <p>So the question is:</p> <blockquote> <p>How to pass the sed <em>parts of the pattern</em> to a shell (function)?</p> </blockquote> <p>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 <em>parts of the pattern</em> as arguments from sed within the sed command.</p> <p>Regards,</p> <p>Salil Joshi</p>
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