Linux - join 2 CSV files

Question

I have 2 CSV files:

file_1 columns: id,user_id,message_id,rate
file_2 columns: id,type,timestamp

The relation between the files is that

Answer 1

With awk you can try something like this -

awk -F, 'NR==FNR{a[$3]=$0;next} ($1 in a){print a[$1]","$3 > "file_3"}' file_1 file_2

Test:

[jaypal:~/Temp] cat file_1     # Contents of File_1
id,user_id,message_id,rate
1,3334,424,44

[jaypal:~/Temp] cat file_2     # Contents of File_2
id,type,timestamp
424,rr,22222

[jaypal:~/Temp] awk -F, 'NR==FNR{a[$3]=$0;next} ($1 in a){print a[$1]","$3 > "file_3"}' file_1 file_2

[jaypal:~/Temp] cat file_3     # Contents of File_3 made by the script
1,3334,424,44,22222