LinuxQuestions.org - [SOLVED] sed - express strings of dots

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sed - express strings of dots

These are contrived examples ...

Code:

st="abcdefghijklmnopqrstuvwxyz"

sed 's/\(.......\)/\1\n/g' <<< $st 

sed 's/\(..........\)/\1\n/g' <<< $st 

sed 's/\(.............\)/\1\n/g' <<< $st

All three seds produce the expected results.

Question: how may the sed be written to parameterize the number of dots?
Is there a shorthand to express a string of 13 dots as '.'{13} or somesuch?
Is there a shorthand to express a string of n dots as '.'{$n} or somesuch?

Daniel B. Martin

Sure. You can either introduce the "[" and "]" characters with "\" to tell sed that they are special

Code:

sed -e 's/$.\{13\}$/\1\n/'

or tell sed to use extended regular expressions, which will make both the parentheses and curly brackets special unless escaped by a backslash.

Code:

sed -r -e 's/(.{13})/\1\n/'

All of the features of extended regular expressions are available in standard expressions. It's just that the need to use backslashes to introduce some characters (i.e., mark them as special) in a standard expression reverses to a need to escape them (mark them as literal) in an extended expression.

Quote:

Originally Posted by rknichols (Post 4918029)

Sure. You can either introduce the "[" and "]" characters with "\" to tell sed that they are special

Code:

sed -e 's/$.\{13\}$/\1\n/'

or tell sed to use extended regular expressions, which will make both the parentheses and curly brackets special unless escaped by a backslash.

Code:

sed -r -e 's/(.{13})/\1\n/'

Thank you, rknichols, this is precisely what is needed.

I generalized your sample code this way:

Code:

echo; echo "Method #1 of LQ Member rknichols"

nc=5

st="abcdefghijklmnopqrstuvwxyz"

sed -e 's/\(.\{'$nc'\}\)/\1\n/g' <<< $st



echo; echo "Method #2 of LQ Member rknichols"

nc=5

st="abcdefghijklmnopqrstuvwxyz"

sed -r -e 's/(.{'$nc'})/\1\n/g' <<< $st

... and it produced the desired results ...

Code:

Method #1 of LQ Member rknichols

abcde

fghij

klmno

pqrst

uvwxy

z



Method #2 of LQ Member rknichols

abcde

fghij

klmno

pqrst

uvwxy

z

SOLVED!

Daniel B. Martin