#!/usr/bin/env perl

use 5.010;
use strict;
use warnings;
use autodie;

{
    say "\n*** Test +< (r+)";
    say 'Open file';
    open my $fh, '+<', 'test1.txt';
    say 'Position in file: ', tell $fh;
    say 'Read to end of file';
    print while <$fh>;
    say 'Position in file: ', tell $fh;
}

{
    say "\n*** Test +> (w+)";
    say 'Open file';
    open my $fh, '+>', 'for_del.txt';
    say 'Position in file: ', tell $fh;
    say 'Read to end of file';
    print while <$fh>;
    say 'Position in file: ', tell $fh;
}

{
    say "\n*** Test +>> (a+)";
    say 'Open file';
    open my $fh, '+>>', 'testq.txt';
    say 'Position in file: ', tell $fh;
    say 'Read to end of file';
    print while <$fh>;
    say 'Position in file: ', tell $fh;
    say 'Write a record';
    say $fh 'r';
    say 'Position in file: ', tell $fh;
    say 'Rewind to start of file';
    seek $fh, 0, 0;
    say 'Position in file: ', tell $fh;
    say 'Read to end of file';
    print while <$fh>;
    say 'Position in file: ', tell $fh;
}

##</code><code>##

ken@titan ~/tmp/pm_11152251_file_rwa
$ ls -l *.txt
-rw-r--r-- 1 ken None 6 May 19 01:41 for_del.txt
-rw-r--r-- 1 ken None 6 May 19 01:16 test1.txt
-rw-r--r-- 1 ken None 6 May 19 01:40 testq.txt

ken@titan ~/tmp/pm_11152251_file_rwa
$ cat test1.txt
1
2
3

ken@titan ~/tmp/pm_11152251_file_rwa
$ cat for_del.txt
z
x
c

ken@titan ~/tmp/pm_11152251_file_rwa
$ cat testq.txt
q
w
e

ken@titan ~/tmp/pm_11152251_file_rwa
$ 

##</code><code>##

ken@titan ~/tmp/pm_11152251_file_rwa
$ ./read_write_append.pl

*** Test +< (r+)
Open file
Position in file: 0
Read to end of file
1
2
3
Position in file: 6

*** Test +> (w+)
Open file
Position in file: 0
Read to end of file
Position in file: 0

*** Test +>> (a+)
Open file
Position in file: 6
Read to end of file
Position in file: 6
Write a record
Position in file: 8
Rewind to start of file
Position in file: 0
Read to end of file
q
w
e
r
Position in file: 8

ken@titan ~/tmp/pm_11152251_file_rwa
$ 

##</code><code>##

ken@titan ~/tmp/pm_11152251_file_rwa
$ ls -l *.txt
-rw-r--r-- 1 ken None 0 May 19 01:42 for_del.txt
-rw-r--r-- 1 ken None 6 May 19 01:16 test1.txt
-rw-r--r-- 1 ken None 8 May 19 01:42 testq.txt

ken@titan ~/tmp/pm_11152251_file_rwa
$ cat test1.txt
1
2
3

ken@titan ~/tmp/pm_11152251_file_rwa
$ cat for_del.txt

ken@titan ~/tmp/pm_11152251_file_rwa
$ cat testq.txt
q
w
e
r

ken@titan ~/tmp/pm_11152251_file_rwa
$