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Remove blank lines in a file using sed

France 211 55 Europe

Japan 144 120 Asia
Germany 96 61 Europe

England 94 56 Europe




Taiwan 55 144 Asia
North Korea 44 2134 Asia


The above is my data file.

There are empty lines in it.

There are no spaces or tabs in those empty lines.

I want to remove all empty lines in the data.

I did a search Delete empty lines using SED has given the perfect answer.

Before that, I wrote two sed code myself:

sed -r 's/nn+/n/g' cou.data
sed 's/nnn*/n/g' cou.data


And I tried awk gsub, not successful either.

awk ' gsub(/nn*/, "n"); print ' cou.data


But they don't work and nothing changes.

Where did I do wrong about my sed code?

n

grep . file

sed '/^$/d' data

1 Answer
1

Use the following sed to delete all blank lines.

sed

sed '/./!d' cou.data


Explanation:

/./

!

d

cou.data

Where did you go wrong?

The following excerpt from How sed Works states:

sed

sed operates by performing the following cycle on each line of input: first, sed reads one line from the input stream, removes any trailing newline, and places it in the pattern space. Then commands are executed; each command can have an address associated to it: addresses are a kind of condition code, and a command is only executed if the condition is verified before the command is to be executed.

When the end of the script is reached, unless the -n option is in use, the contents of pattern space are printed out to the output stream, adding back the trailing newline if it was removed.8 Then the next cycle starts for the next input line.

I've intentionally emboldened the parts which are pertinent to why your sed examples are not working. Given your examples:

sed

sed

nn

nnn

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