I want to find repeated spaces (more than one) and replace them with one space. I tried:

sed -e 's/ []+/ /g' myfile.txt > myfile2.txt

This resulted in an empty file. Why? and how to achieve my goal?


Your command errors out: sed: -e expression #1, char 10: unterminated 's' command so possibly because there is no standard output generated.

Try sed -e 's/ \+/ /g' myfile.txt > myfile2.txt

Also: https://stackoverflow.com/questions/22939323/sed-command-to-replace-multiple-spaces-into-single-spaces


In standard sed, to search for one or more SPC characters, the syntax is:

sed 's/ \{1,\}/ /g'


sed 's/  */ /g'

(that's two spaces before the star). Or to make it more legible:

sed 's/[ ][ ]*/ /g'

Once -E (for extended regular expressions) is added to the standard (which should happen in the next major POSIX release, many implementations already support it), you could also do:

sed -E 's/ +/ /g'

Some sed implementations also understand \+ with basic regex (without -E) as an alias for \{1,\}.

But here, you could just use tr instead:

tr -s ' ' < file.in > file.out

To squeeze the spaces.

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