有时我们需要将某个域之后的所有域打印出来,而且每个记录(行)的域的个数也不一定,所以用“$4,$5,…..$n,….$(NF-1),$NF”穷举是不现时的,我经过测试,总结了一下实现的方法,供大家参考。
// 测试文件内容
[root@cacti tmp]# cat file.txt
x1 x2 x3
x1 x2 x3 x4 x5
x1 x2 x3 x4 x5 x6
x1 x2 x3 x4 x5 x6 x7 x8
x1 x2 x3 x4 x5 x6 x7
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
1) 在NF不够4个的记录(行),将会打印出一个空行;
2) 在输出的结果中,每行结尾多了一个空格;
[root@cacti tmp]# awk '{for(i=4;i<=NF;i++) printf"%s ",$i};NF>4 {print ""}' file.txt
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
// 测试文件内容
[root@cacti tmp]# cat file.txt
x1 x2 x3
x1 x2 x3 x4 x5
x1 x2 x3 x4 x5 x6
x1 x2 x3 x4 x5 x6 x7 x8
x1 x2 x3 x4 x5 x6 x7
x1 x2 x3
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
[root@cacti tmp]# cat file.txt |awk 'NF>4 {a=index($0,$4);print substr($0,a)}'
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
[root@cacti tmp]# cat filexx.txt
x1 x2 x3
x1 x4 x3 x4 x5
x1 x4 x4 x4 x5 x6
x4 x2 x3 x4 x5 x6 x7 x8
x1 x2 x3 x4 x4 x6 x7
(本文件,可以发现$4的字串:x4,在2,3,4,5行,在$4之前的域都有出现过与之相同的字串:x4)
//下面是用上面的方法,结果显然有误的,是将以x4开始的域之后的所有域全打印出来了。
[root@cacti tmp]# cat filexx.txt |awk 'NF>4 {a=index($0,$4);print substr($0,a)}'
x4 x3 x4 x5
x4 x4 x4 x5 x6
x4 x2 x3 x4 x5 x6 x7 x8
x4 x4 x6 x7
[root@cacti tmp]# cat filexx.txt |awk 'NF>4 {$4="z"$4;a=index($0,$4);print substr($0,a)}'
zx4 x5
zx4 x5 x6
zx4 x5 x6 x7 x8
zx4 x4 x6 x7
[root@cacti tmp]# cat filexx.txt |awk 'NF>4 {$4="n"$4;a=index($0,$4);print substr($0,a+1)}'
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x4 x6 x7
[root@cacti tmp]# cat filexx.txt |awk 'BIGIN{FS="[ ]"} NF>4 {$4="n"$4;a=index($0,$4);print substr($0,a+1)}'
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x4 x6 x7
就是将某个(些)域替换成空值,如去除第一个域为:awk '{ $1=""; print $0 }' file.in
// 测试文件内容
[root@cacti tmp]# cat file.txt
x1 x2 x3
x1 x2 x3 x4 x5
x1 x2 x3 x4 x5 x6
x1 x2 x3 x4 x5 x6 x7 x8
x1 x2 x3 x4 x5 x6 x7
[root@cacti tmp]# awk '{ for(i=1;i<=3;i++){$i="a"}; print $0 }' file.txt
a a a
a a a x4 x5
a a a x4 x5 x6
a a a x4 x5 x6 x7 x8
a a a x4 x5 x6 x7
[root@cacti tmp]# awk '{ for(i=1;i<=3;i++){$i=""}; print $0 }' file.txt
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
问题:
1) 在NF不够4个的记录(行),将会打印出一个空行;
2) 在输出的结果中,去除的域会用空格来代替
[root@cacti tmp]# awk 'NF>4 { for(i=1;i<=3;i++){$i=""}; print $0 }' file.txt
x4 x5
x4 x5 x6
x4 x5 x6 x7 x8
x4 x5 x6 x7
本文介绍了三种方法来解决AWK“只打印第N个域之后的所有域”的问题。