tr

[root@lijun ~]#
[root@lijun ~]#echo {1..10} num.txt
1 2 3 4 5 6 7 8 9 10 num.txt
[root@lijun ~]#echo {1..10} > num.txt
[root@lijun ~]#cat num.txt 
1 2 3 4 5 6 7 8 9 10
[root@lijun ~]#tr -s ' ' '\n' <num.txt 
1
2
3
4
5
6
7
8
9
10
[root@lijun ~]#