Delete empty lines using sed

You may have spaces or tabs in your "empty" line. Use POSIX classes with sed to remove all lines containing only whitespace:

sed '/^[[:space:]]*$/d'

A shorter version that uses ERE, for example with gnu sed:

sed -r '/^\s*$/d'

(Note that sed does NOT support PCRE.)

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I am missing the awk solution:

awk 'NF' file

Which would return:

xxxxxx
yyyyyy
zzzzzz

How does this work? Since NF stands for "number of fields", those lines being empty have 0 fields, so that awk evaluates 0 to False and no line is printed; however, if there is at least one field, the evaluation is True and makes awk perform its default action: print the current line.

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sed '/^$/d' should be fine, are you expecting to modify the file in place? If so you should use the -i flag.

Maybe those lines are not empty, so if that's the case, look at this question Remove empty lines from txtfiles, remove spaces from start and end of line I believe that's what you're trying to achieve.

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sed

'/^[[:space:]]*$/d'

'/^\s*$/d'

'/^$/d'

-n '/^\s*$/!p'

grep

.

-v '^$'

-v '^\s*$'

-v '^[[:space:]]*$'

awk

/./

'NF'

'length'

'/^[ \t]*$/ {next;} {print}'

'!/^[ \t]*$/'

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I believe this is the easiest and fastest one:

cat file.txt | grep .

If you need to ignore all white-space lines as well then try this:

cat file.txt | grep '\S'

Example:

s="\
\
a\
 b\
\
Below is TAB:\
    \
Below is space:\
 \
c\
\
"; echo "$s" | grep . | wc -l; echo "$s" | grep '\S' | wc -l

outputs

7
5

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With help from the accepted answer here and the accepted answer above, I have used:

$ sed 's/^ *//; s/ *$//; /^$/d; /^\s*$/d' file.txt > output.txt

`s/^ *//`  => left trim
`s/ *$//`  => right trim
`/^$/d`    => remove empty line
`/^\s*$/d` => delete lines which may contain white space

This covers all the bases and works perfectly for my needs. Kudos to the original posters @Kent and @kev

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Another option without sed, awk, perl, etc

strings $file > $output

strings - print the strings of printable characters in files.

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You can say:

sed -n '/ / p' filename    #there is a space between '//'

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The command you are trying is correct, just use -E flag with it.

sed -E '/^$/d'

-E flag makes sed catch extended regular expressions. More info here

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You are most likely seeing the unexpected behavior because your text file was created on Windows, so the end of line sequence is \r\n. You can use dos2unix to convert it to a UNIX style text file before running sed or use

sed -r "/^\r?$/d"

to remove blank lines whether or not the carriage return is there.

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This works in awk as well.

awk '!/^$/' file
xxxxxx
yyyyyy
zzzzzz

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You can do something like that using "grep", too:

egrep -v "^$" file.txt

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My bash-specific answer is to recommend using perl substitution operator with the global pattern g flag for this, as follows:

$ perl -pe s'/^\n|^[\ ]*\n//g' $file
xxxxxx
yyyyyy
zzzzzz

This answer illustrates accounting for whether or not the empty lines have spaces in them ([\ ]*), as well as using | to separate multiple search terms/fields. Tested on macOS High Sierra and CentOS 6/7.

FYI, the OP's original code sed '/^$/d' $file works just fine in bash Terminal on macOS High Sierra and CentOS 6/7 Linux at a high-performance supercomputing cluster.

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If you want to use modern Rust tools, you can consider:

ripgrep: cat datafile | rg '.' line with spaces is considered non empty cat datafile | rg '\S' line with spaces is considered empty rg '\S' datafile line with spaces is considered empty (-N can be added to remove line numbers for on screen display)

cat datafile | rg '.' line with spaces is considered non empty

cat datafile | rg '\S' line with spaces is considered empty

rg '\S' datafile line with spaces is considered empty (-N can be added to remove line numbers for on screen display)

sd cat datafile | sd '^\n' '' line with spaces is considered non empty cat datafile | sd '^\s*\n' '' line with spaces is considered empty sd '^\s*\n' '' datafile inplace edit

cat datafile | sd '^\n' '' line with spaces is considered non empty

cat datafile | sd '^\s*\n' '' line with spaces is considered empty

sd '^\s*\n' '' datafile inplace edit

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NF is the command of awk you can use to delete empty lines in a file awk NF filename and by using sed sed -r "/^\r?$/d"

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For me with FreeBSD 10.1 with sed worked only this solution:

sed -e '/^[     ]*$/d' "testfile"

inside [] there are space and tab symbols.

test file contains:

fffffff next 1 tabline ffffffffffff

ffffffff next 1 Space line ffffffffffff

ffffffff empty 1 lines ffffffffffff

============ EOF =============

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Using vim editor to remove empty lines

:%s/^$\n//g

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