With (g)awk it can be even worse. $ awk 'BEGIN{while(getline<"phonebook")p[$1]=$2} $1 in p{print $0,p[$1]}' names.tsv If the file `phonebook` doesn't exis

With (g)awk it can be even worse. $ awk 'BEGIN{while(getline<"phonebook")p[$1]=$2} $1 in p{print $0,p[$1]}' names.tsv If the file `phonebook` doesn't exist, this will just sit there politely waiting for you to create the file in your other terminal. (And then when you do, it could crash with `fatal: cannot open file `names.tsv' for reading (No such file or directory)` if that file also doesn't exist. Consistency yay.)