How to perform an action only on the first line?

Question

sed 's/.\(.*\)/\1/' myfile

Say myfile contains:

abc
def
ghi

I want to remove the first character only from the first line but the above removes it from all the line.

Answer 1

Maybe sed '1s/.\(.*\)/\1/' myfile?

Answer 2

can also use awk: awk 'NR==1 {sub(/./,"")} 1'

Answer 3

tail can read from a byte offset, so if your file uses only single-byte characters (typically UTF-8 ASCII), this will work.

It depends on your situaton, whether it is improtant to you or not, but tail is faster than sed... probably becaue sed needs to process each line inndividually, ... But don't use it where there is any chance of the first character using more than one byte.

tail -c +2 "file"  

From man tail

-c, --bytes=N output the last N bytes; alternatively, use +N to output bytes starting with the Nth of each file