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.
set f [open somefile.txt]
while {1} {
set line [gets $f]
if {[eof $f]} {
close $f
break
}
puts "Read line: $line"
}
Read and print out the contents of a file by fixed-size records:
set f [open somefile.dat]
fconfigure $f -translation binary
set recordSize 40
while {1} {
set record [read $f $recordSize]
if {[eof $f]} {
close $f
break
}
puts "Read record: $record"
}