How do you delete one line from a [file]? What kind of file are you
talking about? There aren't, in general, lines in MP3 files, or GIF files, etc.
In fact, most operating systems today don't have operating system calls
that deal in lines. Instead, they come with what I have named, at times,
"meta-read" functions - pieces of code which read in chunks of bytes from
a file, and then, depending on the function's intention, add some code
implementing a common interpretation of some of those bytes.

Most people, asking this particular question, are ''really'' asking
"Assume that I have a plain, traditional, text file - containing 7 bit ASCII 
characters, where newline character indicate the end of a "line". How can
I delete one of those "lines" ."

And honestly, I really believe that's what is being asked. So the following
attempts to address that specific interpretation of this question.

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Well, you could use [sed]. Or you could use something like the following code.



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    set tmpname /tmp/something

    set source [open $filename]
    set destination [open $tmpname w]
    set content [read $source]
    set lines [split $content \n]
    set lines_after_deletion \
       [lreplace $lines $line_number_to_remove $line_number_to_remove]
    puts -nonewline $destination [join $lines_after_deletion \n]
    close $source
    close $destination
    file rename -force $destination $source


Note, however, that in both of these cases, what you are doing are reading the entire file and writing out the entire file, counting lines.


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[Category Example]