[Linux] Read disk capacity

vincent@vincent-Ubuntu:~$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             449G   49G  377G  12% /

1. df -h | awk '{if ($1 == "/dev/sda1") {print $2}}'
449G

2. df -h | grep sda1 | awk '{print $2}'
449G