Remove empty lines in a text file via grep

问题

FILE:

hello

world

foo

bar

How can when remove all the empty new lines in this FILE?

Output of command:

FILE:

hello
world
foo
bar

回答1:

`grep . FILE`

(And if you really want to do it in sed, then: sed -e /^$/d FILE)

(And if you really want to do it in awk, then: awk /./ FILE)

回答2:

Try the following:

grep -v -e '^$'

回答3:

with awk, just check for number of fields. no need regex

$ more file
hello

world

foo

bar

$ awk 'NF' file
hello
world
foo
bar

回答4:

Here is a solution that removes all lines that are either blank or contain only space characters:

grep -v '^[[:space:]]*$' foo.txt

回答5:

Try this: sed -i '/^[ \t]*$/d' file-name

It will delete all blank lines having any no. of white spaces (spaces or tabs) i.e. (0 or more) in the file.

Note: there is a 'space' followed by '\t' inside the square bracket.

The modifier -i will force to write the updated contents back in the file. Without this flag you can see the empty lines got deleted on the screen but the actual file will not be affected.

回答6:

grep '^..' my_file

example

THIS

IS

THE

FILE

EOF_MYFILE

it gives as output only lines with at least 2 characters.

THIS
IS
THE
FILE
EOF_MYFILE

See also the results with grep '^' my_file outputs

THIS

IS

THE

FILE

EOF_MYFILE

and also with grep '^.' my_file outputs

THIS
IS
THE
FILE
EOF_MYFILE

回答7:

Try ex-way:

ex -s +'v/\S/d' -cwq test.txt

For multiple files (edit in-place):

ex -s +'bufdo!v/\S/d' -cxa *.txt

Without modifying the file (just print on the standard output):

cat test.txt | ex -s +'v/\S/d' +%p +q! /dev/stdin

回答8:

Perl might be overkill, but it works just as well.

Removes all lines which are completely blank:

perl -ne 'print if /./' file

Removes all lines which are completely blank, or only contain whitespace:

perl -ne 'print if ! /^\s*$/' file

Variation which edits the original and makes a .bak file:

perl -i.bak -ne 'print if ! /^\s*$/' file

回答9:

If removing empty lines means lines including any spaces, use:

grep '\S' FILE

For example:

$  printf "line1\n\nline2\n \nline3\n\t\nline4\n" > FILE
$  cat -v FILE
line1

line2

line3

line4
$  grep '\S' FILE
line1
line2
line3
line4
$  grep . FILE
line1
line2

line3

line4