awk 笔记之四 getline

getline Sets $0, NF, FNR, and NR
getline var Sets var, FNR, and NR
getline < file Sets $0 and NF
getline var < file Sets var
command | getline Sets $0 and NF
command | getline var Sets var
command |& getline Sets $0 and NF. This is a gawk extension
command |& getline var Sets var. This is a gawk extension