UNIX for Dummies Questions & Answers

File 1:
AB   1
CD   2
EF   3
GH   4

File 2: 
CD  4
EF  5
GH  6
IJ  7

Output
AB 1 X
CD 2 4
EF 3 6
GH 4 6
IJ X 7

#!/usr/bin/env bash

# @(#) s1	Demonstrate join with missing values.

# Section 1, setup, pre-solution, $Revision: 1.26 $".
# Infrastructure details, environment, debug commands for forum posts. 
# Uncomment export command to run as external user: not context, pass-fail.
# export PATH="/usr/local/bin:/usr/bin:/bin"
set +o nounset
pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
LC_ALL=C ; LANG=C ; export LC_ALL LANG
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
edges() { local _f _n _l;: ${1?"edges: need file"}; _f=$1;_l=$(wc -l $_f);
  head -${_n:=3} $_f ; pe "--- ( $_l: lines total )" ; tail -$_n $_f ; }
C=$HOME/bin/context && [ -f $C ] && $C join awk
set -o nounset

cp sacred1 data1
FILE1=data1
cp sacred2 data2
FILE2=data2

# Display sample data files.
pe
specimen $FILE1 $FILE2 expected-output.txt || (
head $FILE1
pe
head $FILE2 
pe 
head expected-output.txt
)

# Section 2, solution.
pl " Results:"
db " Section 2: solution."
join -v 1 <( sort -k1,1 $FILE1 ) <( sort -k1,1 $FILE2 ) |
awk '{print $1,"X"}' >> $FILE2 

join -v 2 <( sort -k1,1 $FILE1 ) <( sort -k1,1 $FILE2 ) |
awk '{print $1,"X"}' >> $FILE1 

join <( sort -k1,1 $FILE1 ) <( sort -k1,1 $FILE2 ) |
tee f1

# Section 3, post-solution, check results, clean-up, etc.
db " Section 3: check solution."
(C=$HOME/bin/pass-fail && [ -f $C ] && $C;exit 0) 

exit 0

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0.8 (lenny) 
bash GNU bash 3.2.39
join (GNU coreutils) 6.10
awk GNU Awk 3.1.5

Whole: 5:0:5 of 4 lines in file "data1"
AB   1
CD   2
EF   3
GH   4

Whole: 5:0:5 of 4 lines in file "data2"
CD  4
EF  5
GH  6
IJ  7

Whole: 5:0:5 of 5 lines in file "expected-output.txt"
AB 1 X
CD 2 4
EF 3 5
GH 4 6
IJ X 7

-----
 Results:
AB 1 X
CD 2 4
EF 3 5
GH 4 6
IJ X 7

-----
 Comparison of 5 created lines with 5 lines of desired results:
 Succeeded -- files have same content.

File 1:
AB 1
CD 1
EF 1

File 2:
EF 2
GH 2
IJ 2

File 3:
IJ 3
KL 3 
MN 3 

File 4:
MN 4
OP 4
RS 4

File 5:
RS 5
TU 5
VW 5

Output:
AB 1 X X X X
CD 1 X X X X
EF 1 2 X X X 
GH X 2 X X X
IJ X 2 3 X X 
KL X X 3 X X 
MN X X 3 4 X 
OP X X X 4 X 
RS X X X 4 5 
TU X X X X 5
VW X X X X 5