Returns 1 if the next read on FILEHANDLE will return end of file or if
FILEHANDLE is not open. FILEHANDLE may be an expression whose value
gives the real filehandle. (Note that this function actually
reads a character and then ungetc
s it, so isn't useful in an
interactive context.) Do not read from a terminal file (or call
eof(FILEHANDLE) on it) after end-of-file is reached. File types such
as terminals may lose the end-of-file condition if you do.
An eof without an argument uses the last file
read. Using eof() with empty parentheses is
different. It refers to the pseudo file formed from the files listed on
the command line and accessed via the <>
operator. Since
<>
isn't explicitly opened, as a normal filehandle is, an
eof() before <>
has been used will cause
@ARGV to be examined to determine if input is
available. Similarly, an eof() after <>
has returned end-of-file will assume you are processing another
@ARGV list, and if you haven't set
@ARGV , will read input from STDIN
; see
I/O Operators in perlop.
In a while (<>)
loop, eof or eof(ARGV)
can be used to detect the end of each file, whereas
eof() will detect the end of the very last file
only. Examples:
- # reset line numbering on each input file
- while (<>) {
- next if /^\s*#/; # skip comments
- print "$.\t$_";
- } continue {
- close ARGV if eof; # Not eof()!
- }
- # insert dashes just before last line of last file
- while (<>) {
- if (eof()) { # check for end of last file
- print "--------------\n";
- }
- print;
- last if eof(); # needed if we're reading from a terminal
- }
Practical hint: you almost never need to use eof in Perl, because the input operators typically return undef when they run out of data or encounter an error.