file: 'rwtest' mode: 'r' readSync: '' writeSync: '' bufferType: 'full' bufSize: '20'

set AAA [string repeat ABCDEFGHIJKLMNOPQRSTUVWXY 4]
set 123 [string repeat 1234567890 10]
set logFilename rwtest-r---full-20.log
set testFilename rwtest-r---full-20.test


set fd [open $testFilename {WRONLY APPEND CREAT TRUNC}]
puts $fd $AAA
puts $fd $123
close $fd

set fd [open rwtest-r---full-20.test r+]
fconfigure $fd -buffering full -buffersize 1024

foreach num {1 2 3 4 5} {
    
    set start [tell $fd]
    puts -nonewline $fd [string repeat $num 11]
    set end [tell $fd]
    
    set repos [tell $fd]
    set char [read $fd 1]
    set final [tell $fd ]
    puts $logFd "$num start = $start end = $end repos = $repos final = $final char = $char"
}
    
close $fd

set fd2 [open rwtest-r---full-20.test r ]
set contents [read $fd2]
close $fd2
puts $logFd \n$contents

1 start = 0 end = 11 repos = 11 final = -1 char = A
2 start = -1 end = -1 repos = -1 final = -1 char = B
3 start = -1 end = -1 repos = -1 final = -1 char = C
4 start = -1 end = -1 repos = -1 final = -1 char = D
5 start = -1 end = -1 repos = -1 final = -1 char = E

ABCDEFGHIJKLMNOPQRSTUVWXYABCDEFGHIJKLMNOPQRSTUVWXYABCDEFGHIJKLMNOPQRSTUVWXYABCDEFGHIJKLMNOPQRSTUVWXY
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
1111111111122222222222333333333334444444444455555555555