Replace columns using a shell

Question

How could I replace column 1 in File1 with column 2 in File2, when a match is found?

File1
id1 36987
id2 75685
id3 12345
id4 12896

File2
id1 ID1
id2 ID2
id3 ID3
id5 ID5

I'd like to write this on another File3, that should look like:

File3
ID1 36987
ID2 75685
ID3 12345
id4 12896

I'm currently (unsuccessfully) trying:

sed `File2.txt | awk '{print "-e s/"$1"/"$2"}'`<<< "File1.txt"

steeldriver · Accepted Answer · 2014-07-10 14:47:12Z

2

With awk

$ awk 'NR==FNR {a[$1]=$2; next}; a[$1] {$1=a[$1]} 1' File2 File1
ID1 36987
ID2 75685
ID3 12345
id4 12896

answered Jul 10, 2014 at 14:47

steeldriver

83.8k12 gold badges124 silver badges175 bronze badges

polym · Accepted Answer · 2014-07-12 10:56:41Z

2

I'd use sed to generate the sed script:

sed 's=^=s/=;s= =/=;s=$=/=' File2 | sed -f- File1

polym

11.1k10 gold badges45 silver badges66 bronze badges

answered Jul 10, 2014 at 14:45

choroba

49.4k7 gold badges92 silver badges118 bronze badges

2 Answers 2