awk在shell脚本中引用变量方式

[root@localhost ~]# a=123

[root@localhost ~]# echo "1" | sed 's/1/"'$a'"/'

"123"

[root@localhost ~]# echo "1" | sed 's/1/'$a'/'

123

[root@localhost ~]# awk 'BEGIN{print '$a'}'

123

[root@localhost ~]# awk 'BEGIN{print '"$a"'}'

123