以下是三个文件 –
emp.txt 7839|BLAKE|PRESIDENT||17-NOV-81|5000||10 7698|KING|MANAGER|7839|01-MAY-81|2850||10 7782|CLARK|MANAGER|7839|09-JUN-81|2450||10 7566|JONES|MANAGER|7839|02-APR-81|2975||40 7788|SCOTT|ANALYST|7566|19-APR-87|3000||50 7902|FORD|ANALYST|7566|03-DEC-81|3000||20 dept.txt 10|ACCOUNTING|NEW YORK 20|RESEARCH|DALLAS 30|SALES|CHICAGO 40|OPERATIONS|BOSTON citycode.txt 1123|NEW YORK 1124|DALLAS 1125|CHICAGO 1126|BOSTON 1127|WASHINGTON
expected output : $0(from emp.txt where $6 >= 2850)+$2(from dept.txt)+$1(from citycode.txt)
7839|BLAKE|PRESIDENT||17-NOV-81|5000||10|ACCOUNTING|1123 7698|KING|MANAGER|7839|01-MAY-81|2850||10|ACCOUNTING|1123 7566|JONES|MANAGER|7839|02-APR-81|2975||40|OPERATIONS|1126 7788|SCOTT|ANALYST|7566|19-APR-87|3000||50|NULL|NULL 7902|FORD|ANALYST|7566|03-DEC-81|3000||20|RESEARCH|1124
Explanation – join these files using common key of emp.txt($NF : outer join on emp.txt–record no 50 doesn’t have common that is why it will print NULL) and
dept.txt($1) where emp($6 >= 2850) and use common column of
dept.txt($NF) and citycode.txt($1). joining two files is an easy task
using common key but how can we join three files together.
解决方法
awk 'BEGIN{ FS=OFS="|" }
FNR==1{ f++ }
f==1{ d[$1]=$2; c[$NF]=$1; next }
f==2 && $NF in c{ c[c[$NF]]=$1; next }
$6 >=2850{
print $0,($NF in d ? d[$NF] : "NULL" ),( $NF in c ? c[$NF] : "NULL")
}' dept.txt citycode.txt emp.txt
说明
awk ' # Call awk
BEGIN{
FS=OFS="|" # Set input and output separator
}
FNR==1{ # FNR will be 1 for each file when awk reads first line
f++ # File counter
}
# use can also do FILENAME == "dept.txt" here but f==1 is easy
f==1{ # for first file dept.txt
d[$1]=$2; # set array d where index is $1 and value is $2 of file dept.txt
c[$NF]=$1; # set array c where index is last field and value is first field of file dept.txt
next # stop processing go to next line
}
# when f equal 2 that is when we read second file citycode.txt
# and last field of current file exists in array c
# there is no point in reading extra line exists in citycode.txt
# we just need whichever city exists in dept.txt
# so $NF in c
f==2 && $NF in c{
# modify array c by empid
# that is index will be the value of array c
# corresponding to last field of current file and
# array c value will be citycode
# Its because to make it easy to access array c value by empid while
# reading emp.txt file
c[c[$NF]]=$1;
# gawk user can delete array element here like below
# if you have gawk uncomment below line
# delete c[$NF]
next # stop processing go to next line
}
$6 >=2850{ # here we read emp.txt if 6th field is greater than or equal to 2850
# Print current record/row/line from emp.txt
# if last field of current file that is
# empid exists in array d then print department else NULL
# if last field of current file that is
# empid exists in array c then print citycode else NULL
print $0,($NF in d?d[$NF]:"NULL"),($NF in c?c[$NF]:"NULL")
}
' dept.txt citycode.txt emp.txt
输入
$cat emp.txt 7839|BLAKE|PRESIDENT||17-NOV-81|5000||10 7698|KING|MANAGER|7839|01-MAY-81|2850||10 7782|CLARK|MANAGER|7839|09-JUN-81|2450||10 7566|JONES|MANAGER|7839|02-APR-81|2975||40 7788|SCOTT|ANALYST|7566|19-APR-87|3000||50 7902|FORD|ANALYST|7566|03-DEC-81|3000||20 $cat dept.txt 10|ACCOUNTING|NEW YORK 20|RESEARCH|DALLAS 30|SALES|CHICAGO 40|OPERATIONS|BOSTON $cat citycode.txt 1123|NEW YORK 1124|DALLAS 1125|CHICAGO 1126|BOSTON 1127|WASHINGTON
产量
$awk 'BEGIN{FS=OFS="|"}FNR==1{f++}f==1{d[$1]=$2;c[$NF]=$1;next}f==2 && $NF in c{c[c[$NF]]=$1;next}$6 >=2850{print $0,($NF in c?c[$NF]:"NULL")}' dept.txt citycode.txt emp.txt
7839|BLAKE|PRESIDENT||17-NOV-81|5000||10|ACCOUNTING|1123
7698|KING|MANAGER|7839|01-MAY-81|2850||10|ACCOUNTING|1123
7566|JONES|MANAGER|7839|02-APR-81|2975||40|OPERATIONS|1126
7788|SCOTT|ANALYST|7566|19-APR-87|3000||50|NULL|NULL
7902|FORD|ANALYST|7566|03-DEC-81|3000||20|RESEARCH|1124