I don't know what command should I use in unix.
Let say I have a file like this:
A 23
B 52
C 36
F 25
and second file with 3 columns:
A aligator 2
B panda 3
C bear 4
D pig 1
E yeti 0
F shark 9
G dog 10
H cat 1
Now I would like to replace first column values (in 1 file) using the second column values (2 file) if the values from the first columns match between files
example of output:
aligator 23
panda 52
bear 36
shark 25
Can anyone help me?
best.
If the files are sorted, you can use join from coreutils:
join -o '2.2 1.2' file1 file2
Output:
aligator 23
panda 52
bear 36
shark 25
The awk is a good tool for this job:
awk 'NR==FNR{a[$1]=$2;next}a[$1]{print $2,a[$1]}' file1 file2
When first file is being read (FN==FNR) fill array a with values from second column and indexed from first column. Then, when second file is processed print its second column and second column from file1.
Output:
aligator 23
panda 52
bear 36
shark 25