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I am having difficulty using sed or grep to extract a piece of text from a string.

An example string I am using is:

|a Milton, John, |d 1608-1674.

I am able to extract 'John' using sed, and some advice on the forums:

sed 's/[^,]*,\([^,]*\),.*/\1/'

But I am struggling with 'Milton'.

  • Do all the input lines start with |a , or are there other possible contents? – JigglyNaga Dec 8 '17 at 17:09
  • "a|" is a constant, as is "d|". Obviously the name and dates vary! – Michael Riordan Dec 8 '17 at 17:18
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Assuming there's the |a at the start of the line, let's change that pattern a bit:

$ echo '|a Milton, John, |d 1608-1674.' | sed -E 's/^\|a ([^,]*), *([^,]*),.*/\1/'
Milton

sed -E uses extended regexes, so we can group with (...) without backslashes. Then we match the leading |a and the space, pick everything up to the next comma to a group ([^,]*),, ignore spaces with ␣*, and pick another group the same way as the first. The ,.* eats the rest of the line, and we can replace all of it with the first group \1 (here Milton), or the second group \2 (John).

Of course, if the |a is there to tell us what this particular field contains, and the fields might be in another order (like |d ... |a ...), then we'd need something different.

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