Shell Programming and Scripting

I have the following input:

1 2 3 \
4 5

1 2 3 4 5 6 7 \
8 \
9 10

And I want to end up with the following:

1 2 3 4 5
1 2 3 4 5 6 7 8 9 10

In other words, how can I join multiple records/lines (2 or more) where the backslash character has been used to extend across multiple lines - using standard UNIX tools such as sed, awk, grep, sh, etc.

The actual application in this instance is joining backslashed multiple lines from the sudoers file.

- CDM

Code:

cat abc.txt | perl -e '
while (<>){ 
chomp;
if (m/\\/) {
      s/\\//g; print "$_" }
 else { 
     print "$_\n";
}
}'

HTH,
PL

Using awk:

Code:

$ awk '
{
    while ($0 ~ /\\$/ ) {
                              getline record;
                              $0 = $0 record
                              }
     print $0
}
' input.txt  | awk '{gsub(/\\/,"")};1'

Code:

awk '{if ($0~/\\$/) {gsub(/\\/,"") ;printf $0} else {print $0}}' abc.txt

Technically there should be a space where the join took place, so IMO the \ and \n should be replaced with a space instead of just deleted:

Code:

sed ':a;N;s/\\\n/ /;ba' infile

This seems to work fine (although only with gsed and not the sed that comes with Solaris 10).

Some of the lines that follow the backslah contain leading spaces/tabs and the backslahes are also preceded by a space. This is what I've found has worked, although it doesn't look particularly pretty:

# sed 's/^[ ]*//g' /etc/sudoers | \ # space & tab between brackets
gsed ':a;N;s/\\\n/ /;ba' | \
sed 's/,[ ]*/,/g' # space & tab between brackets

Can I get all of this into a single sed statement?

Also, could you explain what't happening in the gsed statement you piointed out?

- CDM

This will fare better on Solaris I think -

Code:

sed -e :a -e '/\\$/N; s/\\\n//; ta'

a\
b
becomes ab - no space.
a \
b
becomes a b - one space