Question

How can I delete the first (!) line of a text file if it’s empty, using e.g. sed or other standard UNIX tools. I tried this command:

sed '/^$/d' < somefile

But this will delete the first empty line, not the first line of the file, if it’s empty. Can I give sed some condition, concerning the line number?

With Levon’s answer I built this small script based on awk:

#!/bin/bash

for FILE in $(find some_directory -name "*.csv")
do
    echo Processing ${FILE}

    awk '{if (NR==1 && NF==0) next};1' < ${FILE} > ${FILE}.killfirstline
    mv ${FILE}.killfirstline ${FILE}

done

Answer 1

The simplest thing in sed is:

sed '1{/^$/d}'

Note that this does not delete a line that contains all blanks, but only a line that contains nothing but a single newline. To get rid of blanks:

sed '1{/^ *$/d}'

and to eliminate all whitespace:

sed '1{/^[[:space:]]*$/d}'

Note that some versions of sed require a terminator inside the block, so you might need to add a semi-colon. eg sed '1{/^$/d;}'