Shell Programming and Scripting

joe 123
jane 456

123 left right
456 up down
joe ding dong
jane flip flop

joe 123 ding dong left right
jane 456 flip flop up down

# this grabs the 'left' value
awk 'NR==FNR{a[$1]=$2;next} {print $1,$2,a[$2]}' file2 file1 >> file3
# this grabs the 'right' value
awk 'NR==FNR{a[$1]=$3;next} {print $1,$2,$3,a[$2]}' file2 file3 >> file4

awk 'END {
  for (i = 0; ++i <= FNR;) 
    print r[i]
  }
NR == FNR {
  f[$1] = substr($0, index($0, $2)) 
  next
  }
{ 
  for (i = 0; ++i <= NF;)
    $i in f && r[FNR] = (r[FNR] ? r[FNR] : $0) \
      FS f[$i]
  }' file2 file1

joe joe (skip)
joe 123 (keep)
123 123 (skip)

awk 'END {
  for (i = 0; ++i <= FNR;) 
    if (i in r) print r[i]
  }
NR == FNR {
  f[$1] = substr($0, index($0, $2)) 
  next
  }
$1 != $2 { 
  for (i = 0; ++i <= NF;)
    $i in f && r[FNR] = (r[FNR] ? r[FNR] : $0) \
      FS f[$i]
  }' file2 file1

awk 'NR==FNR{c[$1 FS $2];next} {a[$1]=a[$1] FS $2 FS $3}
    END{for ( i in c) {split(i,x,FS);if (x[1]!=x[2]) print i,a[x[1]],a[x[2]]}}' file1 file2

file1:
john doe 123 left right

file2:
address1 phone1 email1 123
address2 phone2 email2 123

output:
address1 phone1 email1 123 right
address2 phone2 email2 123 right