vlookup work in awk on linux

Question

Hi I have two files containing data: file1:

4,abc
3,xyz
5,fut
6,gfd

file2:

gfd,2.3
xyz,4.5
abc,6.7
fut,3.2

i wish to create a file3 as output file using linux scripting commands:

4,6.7
3,4.5
5,3.2
6,2.3

how do I use FR=NFR etc. awk scripting to do this

Answer 1

With join:

join -t, -1 2 -2 1 -o 1.1,2.2 <(sort -t, -k2 file1) <(sort -t, -k1 file2)

• -t, set delimiter to ,.
• -1 2 the first files join field is the second one.
• -2 1 the second files join field is the first one.
• -o 1.1,2.2 the output format
• <(sort ...) join need input files, which are sorted on the join field.

Answer 2

With awk:

script.awk:

FNR==NR{
    var[$2]=$1
}
FNR!=NR{
    print(var[$1]","$2)
}

Call the script with

awk -F, -f script.awk file1 file2

Answer 3

Similar awk one liner:

awk -F"," 'FNR==NR{var[$2]=$1;next;}{print var[$1]FS$2}'  file1 file2

Output:

$ awk -F"," 'FNR==NR{var[$2]=$1;next;}{print var[$1]FS$2}'  file1.txt file2.txt
6,2.3
3,4.5
4,6.7
5,3.2