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Replacing double spaces with single space

 
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# 1  
Old 09-17-2013
Replacing double spaces with single space
I am looking for a regular expression that uses sed to replace multiple spaces with single spaces on every line where it is not at the start of the line and not immediately before double slashes ('//') or between quotes (").
In its simplest form, it would look like this:
Code:
sed -e 's#  # #g' inputfile

It should therefore perform an inline replacement of this:
Code:
    series of  statements "  with double spaces" in between   // some comments here

into this (only one occurrence of double spaces replaced):
Code:
    series of statements "  with double spaces" in between   // some comments here

However, it should ignore any spaces at the start of the line:
Code:
^(\s)*

And it should ignore everything between quotes:
Code:
"((\\")|[^"(\\")])+"

And it should ignore all white spaces up to the double slashes:
Code:
\s*//

How would I combine all these regular expressions in a single command and using sed?
# 2  
Old 09-17-2013
First attempt
Code:
sed -r 's/([[:alnum:]])  ([[:alnum:]])/\1 \2/' file
    series of statements "  with double spaces" in between   // some comments here

(Doesn't work between double quotes.)
This User Gave Thanks to RudiC For This Post:
figaro
# 3  
Old 09-17-2013
Not a regular expression, nor with sed:
Code:
awk '
{
  for(i=1; i<=NF; i+=2) {
    n=split($i,F,"//")
    while(match(F[1],/[^ ]  +[^ ]/)) F[1]=substr(F[1],1,RSTART) " " substr(F[1],RSTART+RLENGTH-1)
    $i=F[1]
    for (j=2; j<=n; j++) $i=$i "//" F[j]
  }
}
1
' FS=\" OFS=\" file

--
sed with (repeated) regex, does not work 100% correctly within quotes, but it may be a step further:
Code:
sed -e :a -e 's/\([^ "]\)   *\([^ /"]\)\(\/\/.*\)*/\1 \2\3/;ta'  file

Last edited by Scrutinizer; 09-17-2013 at 08:05 PM..
This User Gave Thanks to Scrutinizer For This Post:
figaro
# 4  
Old 09-18-2013
Code:
sed -r 's/([[:alnum:]])  ([[:alnum:]])/\1 \2/' file

I am willing to compromise on the quotes, since they are very rare in my input file. However, the solution does not work when there are more than two spaces. I tried the following, but that left the test line unchanged:
Code:
sed -r 's/([[:alnum:]])(\s*)([[:alnum:]])/\1 \3/'

Code:
sed -e :a -e 's/\([^ "]\)   *\([^ /"]\)\(\/\/.*\)*/\1 \2\3/;ta' file

That one works well, even for the occurrences of quotes that I have.
# 5  
Old 09-18-2013
Well, try this one
Code:
    series of      statements "  with double spaces" in between   // some comments here
sed -r 's/([[:alnum:]]) +([[:alnum:]])/\1 \2/g' file
    series of statements "  with double spaces" in between   // some comments here

This User Gave Thanks to RudiC For This Post:
figaro
 
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