awk命令

awk '{print $1}' Point.cpp 
 awk '{print $2}' Point.cpp 
 awk '{print $3}' Point.cpp 
awk '{print $4}' Point.cpp 
awk '{print $1, "\t" $4, "/t"}' Point.cpp 
awk '{print $1, "\t" $4, "\t"}' Point.cpp 
awk '{print $1, "\t" $2, "\t"}' Point.cpp 
awk '{print NR "\t" $1, "\t" $2, "\t"}' Point.cpp 

横行叫做一个record， 竖行叫做一个field

内部变量
number of record    NR
number of field        NF
中间如果出现空格则将两个字符串拼接在一起
中间写逗号时候会有一个空格

awk 'NF==5{print NR $0}' Point.cpp 
awk '{print $1 $2}' Point.cpp 
awk '{print $1, $2}'
awk 'BEGIN{FS = ","}{print $1 $2}'
awk 'BEGIN{OFS=","; FS=","}{print $1, $2}'
//修改输入输出分隔符为，逗号


awk '{print NR $0}' Point.cpp  X.cpp
//同时awk可以将两个文件拼接起来
 awk '{print NR, FILENAME,$0}' Point.cpp  X.cpp
//打出文件名

awk '{$3="xxxx"; print NR "\t" $0}' Point.cpp 
//将第三列隐藏

awk '{print $NF}' Point.cpp
//打出每行最后一列

awk是一个编程语言可以运算 
awk '{a = 3; b = 1; print a + b}'
awk '{a = 3; b = 1; print a b}'
awk '{a = 3; b = 1; print a * b}'
awk '{a = 3; b = 1; print a / b}'