Linux Combine two files by column

Question

I am trying to combine two files as below (Intersection)

ID     Name  Telephone       
1      John     011
2      Sam      013
3      Jena     014
4      Peter    015

Second file Test2.txt

1       Test1    Test2
2       Test3    Test4
3       Test5    Test6
4       Test7    Test8
5       Test7    Test8
6       Test7    Test8
7       Test7    Test8
8       Test7    Test8
9       Test7    Test8

Then Final result

ID     Name  Telephone    Remark1  Remark2
1      John    011        Test1    Test2
2      Sam     013        Test3    Test4
3      Jena    014        Test5    Test6
4      Peter   015        Test7    Test8

I did like this as below,

awk -F"\t" '
    {key = $1 }
    NR == 1 {header = key}
    !(key in result) {result[key] = $0; next}
    { for (i=2; i <= NF; i++) result[key] = result[key] FS $i }
    END {
        print result[header]
        delete result[header]
        PROCINFO["sorted_in"] = "@ind_str_asc"    
        for (key in result) print result[key]
    }
' Test1.txt Test2.txt > result.txt

And I just notice that this is Union set. Including all data Test1 and Test2.

I would like to show only for Intersection case as what I expected result. (1, 2 ,3 ,4) only

Do you guys have any idea? Thanks!

Answer 1

$ awk -v OFS='\t' '
NR==1   { print $0, "Remark1", "Remark2"; next }
NR==FNR { a[$1]=$0; next }
$1 in a { print a[$1], $2, $3 }
' Test1.txt Test2.txt
ID     Name  Telephone  Remark1 Remark2
1      John     011     Test1   Test2
2      Sam      013     Test3   Test4
3      Jena     014     Test5   Test6
4      Peter    015     Test7   Test8

Answer 2

Another alternative would be pr which is used for formating files to print.

$ pr -tm -w 50 Test1.txt Test2.txt
ID     Name  Telephone   ID Remark1  Remark2
1      John      011     1   Test1    Test2
2      Sam       013     2   Test3    Test4
3      Jena      014     3   Test5    Test6
4      Peter     015     4   Test7    Test8
                         5   Test7    Test8
                         6   Test7    Test8
                         7   Test7    Test8
                         8   Test7    Test8
                         9   Test7    Test8

The most important is the m flag which merges files into columns. The t flag removes headers and footers - since we're not going to print on paper, we don't need them. The last w flag is for setting width.

Answer 3

It is far easier to use the join command:

$ cat a.txt 
ID     Name  Telephone       
1      John     011
2      Sam      013
3      Jena     014
4      Peter    015
$ cat b.txt 
ID     Remark1  Remark2       
1       Test1    Test2
2       Test3    Test4
3       Test5    Test6
4       Test7    Test8
5       Test7    Test8
6       Test7    Test8
7       Test7    Test8
8       Test7    Test8
9       Test7    Test8
$ join a.txt b.txt 
ID Name Telephone Remark1 Remark2
1 John 011 Test1 Test2
2 Sam 013 Test3 Test4
3 Jena 014 Test5 Test6
4 Peter 015 Test7 Test8

Use the column command to pretty print it:

$ join a.txt b.txt | column -t
ID  Name   Telephone  Remark1  Remark2
1   John   011        Test1    Test2
2   Sam    013        Test3    Test4
3   Jena   014        Test5    Test6
4   Peter  015        Test7    Test8

Answer 4

 awk -F"\t" '
     {key = $1 FS $2 FS $3 FS $4}
     NR == 1 {header = key}
     !(key in result) {result[key] = $0; next}
     { for (i=5; i <= NF; i++) result[key] = result[key] FS $i }
     END {
         print result[header]
         delete result[header]
         PROCINFO["sorted_in"] = "@ind_str_asc"    # if using GNU awk
         for (key in result) print result[key]
     }
 ' Test1.txt Test2.txt ... > result.txt