Count number of blank lines in a file

Question

In count (non-blank) lines-of-code in bash they explain how to count the number of non-empty lines.

But is there a way to count the number of blank lines in a file? By blank line I also mean lines that have spaces in them.

Answer 1

One way using grep:

grep -c "^$" file

Or with whitespace:

grep -c "^\s*$" file 

Answer 2

Using Perl one-liner:

perl -lne '$count++ if /^\s*$/; END { print int $count }' input.file

Answer 3

grep -v '\S' | wc -l

(On OSX the Perl expressions are not available, -P option)

Answer 4

grep -cx '\s*' file

or

grep -cx '[[:space:]]*' file

That is faster than the code in Steve's answer.

Answer 5

You can also use awk for this:

awk '!NF {sum += 1} END {print sum}' file

From the manual, "The variable NF is set to the total number of fields in the input record". Since the default field separator is the space, any line consisting in either nothing or some spaces will have NF=0.

Then, it is a matter of counting how many times this happens.

Test

$ cat a
aa dd

ffffd


he      llo
$ cat -vet a # -vet to show tabs and spaces
aa dd$
    $
ffffd$
   $
^I$
he^Illo$

Now let's' count the number of blank lines:

$ awk '!NF {s+=1} END {print s}' a
3

Answer 6

To count how many useless blank lines your colleague has inserted in a project you can launch a one-line command like this:

blankLinesTotal=0; for file in $( find . -name "*.cpp" ); do blankLines=$(grep -cvE '\S' ${file}); blankLinesTotal=$[${blankLines} + ${blankLinesTotal}]; echo $file" has" ${blankLines} " empty lines."  ; done; echo "Total: "${blankLinesTotal}

This prints:

<filename0>.cpp #blankLines
....
....
<filenameN>.cpp #blankLines
Total #blankLinesTotal