How to search, replace and append a pattern to the end of each line

Question

I have the following list of items:

bigBone
fishMarket
dogCollar
...

I need to generate a two character mapping like this:

bigBone -> bb
fishMarket -> fm
dogCollar -> dc
...

How can I create the above mapping using sed?

I have tried something like:

sed -i -r 's/^([a-z]{1})[a-z]+([A-Z]{1})[a-zA-Z]+/ -> \1\L\2/' file

I saw this question, but not sure how to incorporate the concept here. Thanks.

Answer 1

If I understand you correctly then you want to keep the whole line and just append something:

sed -r 's/^([a-z]{1})([a-z]+)([A-Z]{1})([a-zA-Z]+)$/\1\2\3\4 -> \1\L\3/' file

edit:

devnull had to remind me of it that there is an easy solution to this:

sed -r 's/^([a-z]{1})[a-z]+([A-Z]{1})[a-zA-Z]+/& -> \1\L\2/' file

Or, a bit more elegant (than my first try):

sed -r '
h
s/^([a-z]{1})[a-z]+([A-Z]{1})[a-zA-Z]+/ -> \1\L\2/
t append
b
: append
H
g
s/\n//' file

Answer 2

Using GNU sed:

sed -r 's/(.)[^[:upper:]]*(.).*/& -> \1\L\2/' inputfile

For your input, it'd produce:

bigBone -> bb
fishMarket -> fm
dogCollar -> dc

Answer 3

To generalise to fooBarBaz -> fbb, abCdEfGh -> aceg, with GNU sed:

sed -r 's/(.)(.*)/\1\n\2 -> \L\1/;:1
        s/\n([^[:upper:]]*([[:upper:]]))(.*)/\1\n\3\L\2/;t1;s/\n//'

POSIX sed doesn't have \L. So portably, you'd have to resort to using y and manually enter all the characters you want converted to lowercase. Something like:

LC_ALL=C sed '/^\([[:alpha:]]\).*/{
h;s//\1/;y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/;G
s/\(.\).\(.\)\(.*\)/\2\
\3 -> \1/;:1
/.*\n[^A-Z]*\([A-Z]\).*/{h;s//\1/
y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/;G
s/^\(.\)\n\(.*\)\n\([^A-Z]*[A-Z]\)\(.*\)/\2\3\
\4\1/;t1
}
s/\n//;}'

Answer 4

Here it is with a POSIX compliant script. I wasn't aware that POSIX sed leaves the behavior of s///[n]g unspecified, but, sure enough, it is not a well-defined behavior. Anyway, it's easy to handle without it - I just don't like using too many back-references if it can be helped, usually.

sed '/^[a-z]*[A-Z].*$/{ h
    s/\(.\)[^A-Z]*/\1/g
    y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/
    H ; g 
    s/\n/ -> /
    }' <<\DATA
bigBone
fishMarket
dogCollar
DATA

#OUTPUT
bigBone -> bb
fishMarket -> fm
dogCollar -> dc

Answer 5

This answer is just similar to @devnull's,

$ sed 's/\(.\).*\([A-Z]\).*/& -> \1\L\2/g' file
bigBone -> bb
fishMarket -> fm
dogCollar -> dc

Answer 6

If you can use perl, try:

$ perl -MList::Util=first -F// -aple '$_ .= " -> ".$F[0].lc(first{ord() < 97} @F)' file
bigBone -> bb
fishMarket -> fm
dogCollar -> dc