regex - Read variable matched by a .* operation -

modified working solution:

sed -r "s/(\.*)\[/\1\r[/g" 

better solution:

sed -r "s/(.*)\[/\1\r[/g" 

broken down:

s/ (\.*)\[    -string capture followed [ / \1\r[      -line replace /g"   believe subsequent strings, more of these made (\.*) in same order appear left right, variables referenced. 

please try keep answers working sed line description of replace operation.

i want learn how use variables in sed. if have solution, i'm ears, wish learn how manipulate variables in sed.

i've tried

$1, %1 , 1

as combination of these \$1, \%1 \1 , /$1 /%1 /1

to no avail.

here's starting working script replaces matching section blank section.

sed -e "s/\.*\[//g" testfile.txt 

what want script replace (* representing prior (nonwhitespace) string)

*[  

with (no blank lines or tabs in-between either)

* [ 

so figured like

c:\temp>sed -e "s/\.*\[/\1/g" testfile.txt sed: -e expression #1, char 12: invalid reference \1 on `s' command's rhs 

i think want this:

$ cat file.txt  should first line*[and should second $ sed -r 's/([^*]*\*)/\1\n/' file.txt  should first line* [and should second 

note using -r option means don't need escape parens. if don't use -r must replace ( \( , ) \) first capture group within first parens

([^*]*\*) 

which captures before (and including) first *.

the replacement (\1\n) prints first capture group, followed newline, followed rest of line.

and if you're interested in learning sed, check out this tutorial