How do I read first line using cat

问题:

How do i read the first line of a file using cat?

回答1:

You don't need cat. head -1 file will work fine.

回答2:

You don't, use head instead.

head -n 1 file.txt

回答3:

There are many different ways:

sed -n 1p file
head -n 1 file
awk 'NR==1' file

回答4:

You could use cat file.txt | head -1, but it would probably be better to use head directly, as in head -1 file.txt.

回答5:

This may not be possible with cat. Is there a reason you have to use cat?

If you simply need to do it with a bash command, this should work for you:

head -n 1 file.txt

回答6:

cat alone may not be possible, but if you don't want to use head this works:

 cat <file> | awk 'NR == 1'

回答7:

I'm surprised that this question has been around as long as it has, and nobody has provided the pre-mapfile built-in approach yet.

IFS= read -r first_line <file

...puts the first line of the file in the variable expanded by "$first_line", easy as that.

Moreover, because read is built into bash and this usage requires no subshell, it's significantly more efficient than approaches involving subprocesses such as head or awk.

回答8:

You dont need any external command if you have bash v4+

< file.txt mapfile -n1 && echo ${MAPFILE[0]}

or if you really want cat

cat file.txt | mapfile -n1 && echo ${MAPFILE[0]}

:)

回答9:

use the below command to get the first row from a CSVfile

head -1 FileName.csv