Listing 1. Files can have more than one name (or link).

A. The output of the ls -i command:

$ ls -i
30466 footer.ans 
30467 header.ans 
30465 feb.95 
88090 testdir
$ []

B. Creating and listing file links:

$ ls -l feb.95
-rw-r--r-- 1 ray 100 10959 Dec 1 10:15 feb.95
$ ln feb.95 feb.95.link
$ ls -l feb.95*
-rw-r--r-- 2 ray 100 10959 Dec 1 10:15 feb.95
-rw-r--r-- 2 ray 100 10959 Dec 1 10:15 feb.95.link
$ ls -i feb.95*
30465 feb.95
30465 feb.95.link
$ rm feb.95.link
$ ls -l feb.95*
-rw-r--r-- 1 ray 100 10959 Dec 1 10:15 feb.95
$ []

C. Example linking files from one subdirectory to another:

$ ls -l /usr/ray/hidden
-rw-r--r-- 1 ray 100 5478 Dec 3 12:43 code1.c
-rw-r--r-- 1 ray 100 2234 Dec 5 09:25 code2.c
$ ln /usr/ray/hidden/code1.c /usr/ray/shared/program1.c
$ ln /usr/ray/hidden/code2.c /usr/ray/shared/program2.c
$ ls -l /usr/ray/shared
-rw-r--r-- 2 ray 100 5478 Dec 3 12:43 program1.c
-rw-r--r-- 2 ray 100 2234 Dec 5 09:25 program2.c
$ []

Listing 2. Merging addresses from a data base with a letter to create form letters.

A. Sample lines from the address data base:

Decotex Inc:Dutchess Court Plaza:Pawling, NY 12564:Karl Kullling
Berkley Decision Systems:803 Pine Street:Santa Cruz, CA 95062:Ray Swartz

B. Listing of the merge.awk program:

1 #! /bin/sh
2 # @(#) merge.awk Form-letter address merge program
3 # Address-line fields: company:address:city, state, ZIP:recipient name
4 #
5 if [ $# -ne 2 ]; then
6 echo "Usage: $0 form-letter-file address-file" >&2
7 exit 1
8 fi
9 (cat $1; echo "@@@" ; cat $2) |
10 awk 'addrs == 1 { printf "%s\n%s\n%s\n%s\n\n", $4, $1, $2, $3
11 for (i = 1; i < nbrLines; i++)
12 print letter[i]
13 print "^L" }
14 addrs == 0 { letter[++nbrLines] = $0 }
15 /^@@@$/ { addrs = 1
16 FS = ":"}'

C. Listing of the merge.perl program:

1 #!/usr/local/bin/perl
2 # @(#) merge.perl Form-letter address merge program
3 
4 # Rough check for valid arguments:
5 $#ARGV == 1 || die "Usage: $0 form-letter-file address-file";
6 
7 # Open the form letter file or bust:
8 open(LETTER, $ARGV[0]) || die "Can't open form letter file\n" ;
9 
10 # Read contents of form letter into "letter" array:
11 @letter = <LETTER> # all lines in one gulp
12 
13 # Determine number of lines in "letter" file:
14 $letlen = $#letter; # Lines in "letter" file = array element count
15 
16 # Open the address file or bust:
17 open(ADDRESS, $ARGV[1]) || die "Can't open address file\n";
18 
19 # Prefix address-line fields to form letter, output:
20 while ($line = <ADDRESS>) { # loop once for each address
21 chop($line);
22 @f = split(/:/, $line); # split into fields on :
23 print "$f[3]\n$f[0]\n$f[1]\n$f[2]\n\n";
24 foreach $line (@letter) { # print the form letter
25 print $line;
26 }
27 print "\f\n"; # Separate each letter with a form-feed character
28 }