Most efficient way to use first column of file1 as prefix for all lines in file2-CodePudding

I have two files with equal amount of lines. I want to add each value of column 1 to become the prefix of each line in file 2 and separate each value of file2 by one whitespace. File2 is very large and has more than 70 million columns.

Example: Input file 2

10000
10019

Input file 1

Ind1
Ind2

Output

Ind1 1 0 0 0 0 
Ind2 1 0 0 1 9

Q: How can this be done efficiently?

EDIT I : I already looked for solutions to add different prefixes to each line e.g. here but was unable to adjust the solution so that I can iterate over the values of the first column of another file.

EDIT II : Using the answer from @Gilles I came up with this:

awk ' { print $1 } ' file1 <(sed 's/./& /g' file2) > output

CodePudding user response：

$ paste -d '' file2 <(sed 's/./& /g' file1) 
Ind1 1 0 0 0 0 
Ind2 1 0 0 1 9

CodePudding user response：

Using any awk:

$ awk '{head=$0} (getline tail < "file2") > 0{gsub(/./," &",tail); print head tail}' file1
Ind1 1 0 0 0 0
Ind2 1 0 0 1 9

or if the whole contents of file1 fit in memory:

$ awk 'NR==FNR{a[FNR]=$0; next} {gsub(/./," &"); print a[FNR], $0}' file1 file2