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
grep . FILE
(And if you really want to do it in sed, then: sed -e /^$/d FILE)
(And if you really want to do it in awk, then: awk /./ FILE)
Try the following:
grep -v -e '^$'
with awk, just check for number of fields. no need regex
$ more file
hello
world
foo
bar
$ awk 'NF' file
hello
world
foo
bar
Here is a solution that removes all lines that are either blank or contain only space characters:
grep -v '^[[:space:]]*$' foo.txt
Try this: sed -i '/^[ \t]*$/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.
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
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
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
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:
来源：https://stackoverflow.com/questions/1611809/remove-empty-lines-in-a-text-file-via-grep