Programming Perl, 4th Edition

eof

eof FILEHANDLE
eof()
eof

This function returns true if the next read on FILEHANDLE would return end-of-file or if FILEHANDLE is not open. FILEHANDLE may be an expression whose value gives the real filehandle or a reference to a filehandle object of some sort. An eof without an argument returns the end-of-file status for the last file read. An eof() with empty parentheses () tests the ARGV filehandle (most commonly seen as the null filehandle in <>). Therefore, inside a while (<>) loop, an eof() with parentheses will detect the end of only the last of a group of files. Use eof (without parentheses) to test each file in a while (<>) loop. For example, the following code inserts dashes just before the last line of the last file:

while (<>) {
    if (eof()) {
        say "–" x 30;
    }
    print;
}

On the other hand, this script resets line numbering on each input file:

# reset line numbering on each input file
while (<>) {
    next if /^\s*#/;        # skip comments
    print "$.\t$_";
} continue {
    close ARGV if eof;      # Not eof()!
}

Like “$” in a sed program, eof tends to show up in line number ranges. Here’s a script that prints lines from /pattern/ to the end of each input file:

while (<>) {
    print if /pattern/ .. eof;
}

Here, the flip-flop operator (..) evaluates the pattern match for each line. Until the pattern matches, the operator returns false. When it finally matches, the operator starts returning true, causing ...