Cfrgtkky

In a text file, ignoring any trailing whitespace at the end of each line, I assume that if a line is not ended with a digit, then there is a line break between the line and the next line, and I would like to find these line breaks and then concatenate them into one line. For example

line 1

li

ne 2

There is a line break between the second and the third lines and I should modify the file to be

line 1

line 2

To find such line breaks, I need to do multiline matching. I does it by changing record separator, but the following doesn't work:

$ awk 'BEGIN{RS="";}; { if (match($0, /[^[:digit:] ] *n/)) print $0;} ' inputfile

To concatenate two lines separated by a line break, I am still wondering.

Thanks.

You could run something along the lines of

awk 'BEGIN{RS=SUBSEP; ORS="" } {print gensub(/([^0-9])n/,"\1","g",$0)}' ex

• 
  RS=SUBSEP sets the Register Separator to a value that is never present in a text file (slurps the input file to $0)


• then do you favorite multiline transformation

I would address it differently: by looping over the input until you find a "line-ending condition":

awk '{ 

       line=$0; 

       while($0 !~ /[[:digit:]] *$/ && getline > 0) { 

         line=line$0; 

       }

       print line

     }' < input

On an extended input file of:

line 1

li

ne 2

li

ne 

number 3

line 4

Or, more verbosely (to see the trailing space):

$ cat -e input

line 1$

li$

ne 2$

li$

ne $

number 3$

line 4$

The output is:

line 1

line 2

line number 3

line 4

$ cat file

line 1

li

ne 2

lo

ng li

ne 3

$ awk 'line ~ /[0-9]$/ { print line; line = "" } { line = line $0 } END { print line }' file

line 1

line 2

long line 3

This accumulates an "output line" in the variable line, and whenever this variable ends with a digit, it is printed and reset. It is also printed at the very end to output the last line (whether complete or not).

Approximate sed equivalent (but with an explicit loop):

$ sed -e ':again' -e '/[0-9]$/{ p; d; }; N; s/n//' -e 'tagain' file

line 1

line 2

long line 3

Small GNU sed?

sed ':L; /[0-9] *$/!{N; bL;}; s/n//g' file