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Do you have a method to quickly remove the first line of a file in bash shell ? I mean using sed or stuff like that.

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3 Answers 3

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One-liners in reverse order of length, portable unless noted.

sed (needs GNU sed for -i):

sed -i 1d file

ed (needs e.g. bash for $'...' expansion and here string):

ed file <<< $'1d\nw\nq'

awk:

awk NR\>1 infile > outfile

tail:

tail -n +2 infile > outfile

read + cat:

(read x; cat > outfile) < infile

bash built-ins:

while IFS= read -r; do ((i++)) && printf %s\\n "$REPLY" >> outfile; done < infile
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  • 4
    or ed file1 <<< $'1d\nw\nq' May 16, 2011 at 14:58
  • 1
    In my case, tail is 15 times slower than sed. tail needs 13.5s, sed needs 0.85s. My file has ~1M lines, ~100MB. MacBook Air 2013 with SSD. Feb 1, 2016 at 16:26
  • I like the awk cmd the best. Dec 6, 2021 at 20:20
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$ tail -n +2 <<< $'1\n2\n3'
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0

Using dd

fn="The-BIG-FILE.txt"
fll=$(( $(head -n 1 $fn | wc -c) + 1))
dd if="$fn" of="${fn}.out" bs=1M iflags=skip_bytes skip=$fll
echo "Files differ by $(( $(find $fn* -printf "%s - \n" ; echo "0") )) bytes. First line of $fn is $fll bytes."

Add any iflags= and oflags= you might need - with commas separating them.

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