How to make the 'cut' command treat same sequental delimiters as one?

Question

I'm trying to extract a certain (the fourth) field from the column-based, 'space'-adjusted text stream. I'm trying to use the cut command in the following manner:

cat text.txt | cut -d " " -f 4

Unfortunately, cut doesn't treat several spaces as one delimiter. I could have piped through awk

awk '{ printf $4; }'

or sed

sed -E "s/[[:space:]]+/ /g"

to collapse the spaces, but I'd like to know if there any way to deal with cut and several delimiters natively?

Answer 1

Try:

tr -s ' ' <text.txt | cut -d ' ' -f4 

From the tr man page:

 -s, --squeeze-repeats   replace each input sequence of a repeated character                         that is listed in SET1 with a single occurrence                         of that character 

Answer 2

As you comment in your question, awk is really the way to go. To use cut is possible together with tr -s to squeeze spaces, as kev's answer shows.

Let me however go through all the possible combinations for future readers. Explanations are at the Test section.

tr | cut

tr -s ' ' < file | cut -d' ' -f4 

awk

awk '{print $4}' file 

bash

while read -r _ _ _ myfield _ do    echo "forth field: $myfield" done < file 

sed

sed -r 's/^([^ ]*[ ]*){3}([^ ]*).*/\2/' file 

---

Tests

Given this file, let's test the commands:

$ cat a this   is    line     1 more text this      is line    2     more text this    is line 3     more text this is   line 4            more    text 

tr | cut

$ cut -d' ' -f4 a is                         # it does not show what we want!   $ tr -s ' ' < a | cut -d' ' -f4 1 2                       # this makes it! 3 4 $ 

awk

$ awk '{print $4}' a 1 2 3 4 

bash

This reads the fields sequentially. By using _ we indicate that this is a throwaway variable as a "junk variable" to ignore these fields. This way, we store $myfield as the 4th field in the file, no matter the spaces in between them.

$ while read -r _ _ _ a _; do echo "4th field: $a"; done < a 4th field: 1 4th field: 2 4th field: 3 4th field: 4 

sed

This catches three groups of spaces and no spaces with ([^ ]*[ ]*){3}. Then, it catches whatever coming until a space as the 4th field, that it is finally printed with \1.

$ sed -r 's/^([^ ]*[ ]*){3}([^ ]*).*/\2/' a 1 2 3 4