Compare headers of two delimited text files - bash

Question

File1.txt(base file)
header1|header2|header3|header4
1|2|3|4
File2.txt
header1|header10|header3|header4
5|6|7
Desired O/P
header2 is missing in file 2 at position 2
header10 is addition in file 2 at position 2
I need to compare two file header and need to display missing header or addition columns with respect to base file header list.

Answer 1

I would try it with the diff command like this:
diff <(head -n1 fh1.txt | tr "|" "\n") <( head -n1 fh2.txt | tr "|" "\n")
where fh1.txt and fh2.txt are your files. The output gives the information that you want but it is not so verbose.

Answer 2

You can use awk, like this:
check.awk
# In the first line of every input file save the headers
FNR==1{
headers[f++]=$0
}
# Once all lines of input have been processed ...
END{
# split() returns the number of items. The resulting
# arrays 'a|b_headers' will be indexed starting from 1
lena = split(headers[0],a_headers,"|")
lenb = split(headers[1],b_headers,"|")
for(h=1;h<=lena;h++) {
if(a_headers[h] != b_headers[h]) {
print a_headers[h] " missing from file2 at column " h
}
}
for(h=1;h<=lenb;h++) {
if(b_headers[h] != a_headers[h]) {
print b_headers[h] " missing from file1 at column " h
}
}
}
Call it like this:
awk -f check.awk File1.txt File2.txt
Output:
header2 missing from file2 at column 2
header10 missing from file1 at column 2