mjhjmtu

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 'BEGINRS="";; 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 'BEGINRS=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