Remove empty lines in a text file via grep

Question

FILE:

hello

world

foo

bar

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

Output of command:

Answer 1

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.

Answer 2

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

$ more file
hello

world

foo

bar

$ awk 'NF' file
hello
world
foo
bar

Answer 3

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

Answer 4

Simplest Answer -----------------------------------------

[root@node1 ~]# cat /etc/sudoers | grep -v -e ^# -e ^$
Defaults   !visiblepw
Defaults    always_set_home
Defaults    match_group_by_gid
Defaults    always_query_group_plugin
Defaults    env_reset
Defaults    env_keep =  "COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS"
Defaults    env_keep += "MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE"
Defaults    env_keep += "LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES"
Defaults    env_keep += "LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE"
Defaults    env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY"
Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin
root    ALL=(ALL)       ALL
%wheel  ALL=(ALL)       ALL
[root@node1 ~]#

Answer 5

Try the following:

grep -v -e '^$'