Shell scripting, replace the characters using sed - shell

Question

In shell scripting, i want to replace 1bc1034gf45dna22 (16 characters total) with 1b:c1:03:4g:f4:5d:na:22 (seperated by colon) using sed.
Edit
I have tried
sed 's/\w{2}/\w{2}:/g' a.txt > b.txt
where a.txt has
1bc1034gf45dna22

Answer 1

Too Many Edge Cases
Sed is not an ideal tool for this job, because there are just too many edge cases. If you have very regular data and a known corpus then that's fine, but in some cases you need something more powerful that can act on pieces of a line independently after matching/capturing the text of interest. For example, given an input file containing:
foo 1bc1034gf45dna22 bar
you might need to extract the second column, transform it, and then substitute it in place. You might do this with Ruby as follows:
$ echo 'foo 1bc1034gf45dna22 bar' |
ruby -pe '
if /(?<str>\p{Alnum}{16})/ =~ $_
$_.sub!(str, str.scan(/../).join(?:))
end'
This correctly yields:
foo 1b:c1:03:4g:f4:5d:na:22 bar

Answer 2

Does
sed -e 's/../&:/g' -e 's/:$//' a.txt > b.txt
or
sed -e 's/\(..\)/\1:/g' -e 's/:$//' a.txt > b.txt
work for you?

Answer 3

This might work for you (GNU sed):
sed 's/\w\w\B/&:/g' file

Answer 4

why not sed 's/1bc1034gf45dna22/1b:c1:03:4g:f4:5d:na:2/g' file ?

Answer 5

You could:
sed -i 's/\(\w\{2\}\)/\1:/g' file
This would also append a : to the end of the string. Since we cannot use positive lookahead in our sed regex syntax, we would then need to:
sed -i 's/:$//g' file
Notice that we used inplace editing for sed therefore the file will in this way altered.
Alternatively, you could use perl to use a regex that would have been /(\w{2})(?=\w{2})/$1:/g

Answer 6

With GNU/sed on any GNU/Linux distro you can use extentded regular expressions. This will convert a string of any length to a string where each two letters are separated by a colon:
echo 1bc1034gf45dna22 | sed -re 's/(\w{2})/\1:/g' -e 's/:$//'
On your AIX platform, you can leverage awk:
echo 1bc1034gf45dna22 | awk '
BEGIN { FS=""; ORS=""; }
{
for (i=1; i <=NF; i++) {
if (i > 1 && (i + 1) % 2 == 0) {
print(":");
}
print($i);
}
}'

Answer 7

Well, there's always the brute-force method:
sed 's/\<'\
'\([0-9a-z][0-9a-z]\)'\
'\([0-9a-z][0-9a-z]\)'\
'\([0-9a-z][0-9a-z]\)'\
'\([0-9a-z][0-9a-z]\)'\
'\([0-9a-z][0-9a-z]\)'\
'\([0-9a-z][0-9a-z]\)'\
'\([0-9a-z][0-9a-z]\)'\
'\([0-9a-z][0-9a-z]\)'\
'\>/\1:\2:\3:\4:\5:\6:\7:\8/g'
With no leading spaces on the continuation lines the shell pastes the strings together properly.