join multiple files

Question

I am using the standard join command to join two sorted files based on column1. The command is simple join file1 file2 > output_file.

But how do I join 3 or more fil

Answer 1

man join:

NAME
       join - join lines of two files on a common field

SYNOPSIS
       join [OPTION]... FILE1 FILE2

it only works with two files.

if you need to join three, maybe you can first join the first two, then join the third.

try:

join file1 file2 | join - file3 > output

that should join the three files without creating an intermediate temp file. - tells the join command to read the first input stream from stdin

Answer 2

I created a function for this. First argument is the output file, rest arguments are the files to be joined.

function multijoin() {
    out=$1
    shift 1
    cat $1 | awk '{print $1}' > $out
    for f in $*; do join $out $f > tmp; mv tmp $out; done
}

Usage:

multijoin output_file file*