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awk打开多个文件的方法
1、当awk读取的文件只有两个的时候,比较常用的有三种方法
(1)awk ‘NR==FNR{...}NR>FNR{...}‘ file1 file2
(2)awk ‘NR==FNR{...}NR!=FNR{...}‘ file1 file2
(3)awk ‘NR==FNR{...;next}{...}‘ file1 file2
next表示下一个命令不被执行
2、当awk处理的文件超过两个时,显然上面那种方法就不适用了。因为读第3个文件或以上时,也满足NR>FNR (NR!=FNR),显然无法区分开来。
所以就要用到更通用的方法了:
(1)ARGIND 当前被处理参数标志: awk ‘ARGIND==1{...}ARGIND==2{...}ARGIND==3{...}... ‘ file1 file2 file3 ...
(2)ARGV 命令行参数数组: awk ‘FILENAME==ARGV[1]{...}FILENAME==ARGV[2]{...}FILENAME==ARGV[3]{...}...‘ file1 file2 file3 ...
(3)把文件名直接加入判断: awk ‘FILENAME=="file1"{...}FILENAME=="file2"{...}FILENAME=="file3"{...}...‘ file1 file2 file3 ...
举例说明,这个例子在面试的时候问过。
a.txt中有一列:
A
B
C
D
E
b.txt中有两列:
A hello world
A good morning
B what
C sad
D interview someone
D feeling bad
E not so good
E want to be happy
F fail to pass the exam
G good result
则打印出b.txt中的行,满足b.txt中第一列等于a.txt的第一列。
#! /usr/bin/ksh print "Method1:########" awk ‘ARGIND==1{test[NR]=$1} ARGIND==2{for(i in test){if(test[i]==$1){print $0}}}‘ a.txt b.txt print "\nMethod2:########" #the ‘{" must at the same line of the NR!=FNR gawk ‘NR==FNR{test[NR]=$1} NR!=FNR{ for( i in test) { if(test[i]==$1) print $0 } }‘ a.txt b.txt print "\nMethod3:########" gawk ‘NR==FNR{test[NR]=$1} NR>FNR{ for( i in test) { if(test[i]==$1) print $0 } }‘ a.txt b.txt print "\nMethod4:########" gawk ‘NR==FNR{test[NR]=$1;next} { for( i in test) { if(test[i]==$1) print $0 } }‘ a.txt b.txt print "\nMethod5:########" gawk ‘FILENAME==ARGV[1]{test[NR]=$1} FILENAME==ARGV[2]{ for( i in test) { if(test[i]==$1) print $0 } }‘ a.txt b.txt print "\nMethod6:########" gawk ‘FILENAME=="a.txt"{test[NR]=$1} FILENAME=="b.txt"{ for( i in test) { if(test[i]==$1) print $0 } }‘ a.txt b.txt
输出结果为:
Method1:########
A hello world
A good morning
B what
C sad
D interview someone
D feeling bad
E not so good
E want to be happy
Method2:########
A hello world
A good morning
B what
C sad
D interview someone
D feeling bad
E not so good
E want to be happy
Method3:########
A hello world
A good morning
B what
C sad
D interview someone
D feeling bad
E not so good
E want to be happy
Method4:########
A hello world
A good morning
B what
C sad
D interview someone
D feeling bad
E not so good
E want to be happy
Method5:########
A hello world
A good morning
B what
C sad
D interview someone
D feeling bad
E not so good
E want to be happy
Method6:########
A hello world
A good morning
B what
C sad
D interview someone
D feeling bad
E not so good
E want to be happy
awk打开多个文件的方法