Inner join on two text files

Question

Looking to perform an inner join on two different text files. Basically I\'m looking for the inner join equivalent of the GNU join program. Does such a thing exist? If not,

Answer 1

Here's an awk option, so you can avoid the bash dependency (for portability):

$ awk -F'|' 'NR==FNR{check[$0];next} $2 in check' file2 file1

How does this work?

• -F'|' -- sets the field separator
• 'NR==FNR{check[$0];next} -- if the total record number matches the file record number (i.e. we're reading the first file provided), then we populate an array and continue.
• $2 in check -- If the second field was mentioned in the array we created, print the line (which is the default action if no actions are provided).
• file2 file1 -- the files. Order is important due to the NR==FNR construct.