Code:

proc read_last_line {fname} {  set fp [open $fname r]  # pos is the position in the file (in reverse)  # we start at 512 bytes from the end of the file  set pos 512  while {1} {    # this moves to $pos bytes before the end of the file    seek $fp -$pos end    # read to the end of the file    set data [read -nonewline $fp]    # we may have read multiple lines (if less than 512 bytes)    set lines [split $data \n]    if {[llength $lines] > 1} {      # yup, we read at least 1 line and part of another, so we know      # we for sure have the complete last line, we're done      close $fp      return [lindex $lines end]    } elseif {[tell $fp] < $pos} {      # Well, before I had >=, but it should be <.      # This happens if the entire file is < 512 bytes, and we didn't read      # in multiple lines... therefore the file is a single line and we read the      # whole thing, so we're done.      close $fp      return $data    }    # Now we just repeat the process, adding another 512 bytes    incr pos 512  }}

Code:

proc read_last_line {fname} {  set fp [open $fname r]  set pos 512  while {1} {    seek $fp -$pos end    set data [read -nonewline $fp]    set lines [split $data \n]    if {[llength $lines] > 1} {      close $fp      return [lindex $lines end]    } elseif {[tell $fp] >= $pos} {      close $fp      return $data    }    incr pos 512  }}