'''eof''' a [Tcl Commands%|%build-in] command, checks for an end-of-file
condition on a [channel].  The name is an acronym for ''End Of File''.



** See Also **

   [FMM%|%Frequently-Made Mistakes in Tcl] ,by [Cameron Laird]:   Describes a common [[eof] mistake

   [fblocked]:   detect whether a read operation exhausted all available input



** Documentation **

    [http://www.tcl.tk/man/tcl/TclCmd/eof.htm%|%official reference]:   



** Synopsis **

    :   '''eof''' ''channelId''



** Description **

[[`eof`] is used to determine whether the channel has reached the end of input.

Returns `1` if an end of file condition occurred during the most recent input
operation on ''channelId'' (such as '''[gets]'''), `0` otherwise.

''ChannelId'' must be an identifier for an open channel such as a [Tcl]
standard channel ('''[stdin]''', '''[stdout]''', or '''[stderr]'''), the return
value from an invocation of '''[open]''' or '''[socket]''', or the result of a
channel creation command provided by a Tcl extension. 


When [[`eof`] is true for a socket channel, it's time to close that socket. 


[[`eof`] is only true ''after'' no more characters can be read from the
channel, so usually you'll want to first try to read the channel, and if you
only get back the empty, use [[`eof`] to determine whether you've reached the
end of the channel:

======
while 1 {
        if {[gets $chan line] > 0} {
                #do stuff
        } else {
                if {[eof $chan]} {
                        close $chan
                        break
                } else {
                        #haven't reached the end of a non-blocking channel
                        #give it a moment
                        after 20 
                }
        }
}
======

instead of

======
#warning! Bad Code!
while {![eof $fp]} {
   gets $fp line
   if [eof $fp] break ;# otherwise loops one time too many
   ...
} ;# RS  
======


Another alternative:

======
gets $fp line
while {![eof $fp]} {
    # process line
    gets $fp line
}
======

Also, [gets] returns -1 when it encountered an EOF. Hence, I now always write:
======
while {[gets $fp line] >= 0} {
    ...
}
close $fp
======

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