Use head -n -0 to get all items in list
Published:
You may know that you can use head -n $n to get the first N lines of a list. But you may not know that you can supply n=-0 to get all items in the list.
I use this frequently when I want to test some preprocessing script on a sample of a dataset before running on the whole dataset. Here is a snippet I use sometimes. It gets the first N lines if an argument is given, otherwise all lines.
#!/bin/bash
n="$1"
if [ -z "$n" ]
then
n="-0"
fi
head -n $n data.txt
Here is the snippet in action.
$ seq 1 10 > data.txt
$ bash head_script.sh 1
1
$ bash head_script.sh 5
1
2
3
4
5
$ bash head_script.sh
1
2
3
4
5
6
7
8
9
10