Remove empty lines in a text file via grep
LinuxGrepText ProcessingLinux Problem Overview
FILE:
hello
world
foo
bar
How can I remove all the empty new lines in this FILE?
Output of command:
FILE:
hello
world
foo
bar
Linux Solutions
Solution 1 - Linux
grep . FILE
(And if you really want to do it in sed, then: sed -e /^$/d FILE)
(And if you really want to do it in awk, then: awk /./ FILE)
Solution 2 - Linux
Try the following:
grep -v -e '^$'
Solution 3 - Linux
with awk, just check for number of fields. no need regex
$ more file
hello
world
foo
bar
$ awk 'NF' file
hello
world
foo
bar
Solution 4 - Linux
Here is a solution that removes all lines that are either blank or contain only space characters:
grep -v '^[[:space:]]*$' foo.txt
Solution 5 - Linux
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
See also:
Solution 6 - Linux
Try this: sed -i '/^[ \t]*$/d' file-name
It will delete all blank lines having any no. of white spaces (spaces or tabs) i.e. (0 or more) in the file.
Note: there is a 'space' followed by '\t' inside the square bracket.
The modifier -i will force to write the updated contents back in the file. Without this flag you can see the empty lines got deleted on the screen but the actual file will not be affected.
Solution 7 - Linux
Simplest Answer -----------------------------------------
[root@node1 ~]# cat /etc/sudoers | grep -v -e ^# -e ^$
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 ~]#
Solution 8 - Linux
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
Solution 9 - Linux
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
Solution 10 - Linux
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
Solution 11 - Linux
If you want to know what the total lines of code is in your Xcode project and you are not interested in listing the count for each swift file then this will give you the answer. It removes lines with no code at all and removes lines that are prefixed with the comment //
Run it at the root level of your Xcode project.
find . \( -iname \*.swift \) -exec grep -v '^[[:space:]]*$' \+ | grep -v -e '//' | wc -l
If you have comment blocks in your code beginning with /* and ending with */ such as:
/*
This is an comment block
*/
then these will get included in the count. (Too hard).