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

Question

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

Answer 1

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]}

:)

Answer 2

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.

Answer 3

There are many different ways:

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

Answer 4

There is plenty of good answer to this question. Just gonna drop another one into the basket if you wish to do it with lolcat

lolcat FileName.csv | head -n 1

Answer 5

Adding one more obnoxious alternative to the list:

perl -pe'$.<=1||last' file
# or 
perl -pe'$.<=1||last' < file
# or
cat file | perl -pe'$.<=1||last'

Answer 6

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