问题
I am dealing with a file where fields are separated by a single space.
awk interprets the FS " " as "one or more whitespace", which misreads my file when one of the fields is empty.
I tried using "a space not followed by a space"( " (?! )" ) as FS but awk does not support negative lookahead. Simple google queries like "single space field separator awk" only sent me to the manual page explaining the special treatment of FS=" ". I must have missed the relevant manual page...
How can I use a single space as field separator with awk?
回答1:
this should work
$ echo 'a b' | awk -F'[ ]' '{print NF}'
5
where as, this treats all contiguous white space as one.
$ echo 'a b' | awk -F' ' '{print NF}'
2
based on the comment, it need special consideration, empty string or white space as field value are very different things probably not a good match for a white space separated content.
I would suggest preprocessing with cut and changing the delimiters, for example
$ echo 'a b' | cut -d' ' -f1,3,5 --output-delimiter=,
a,,b
来源：https://stackoverflow.com/questions/36008369/single-space-as-field-separator-with-awk