diff options
| -rw-r--r-- | pod/perlfunc.pod | 33 |
1 files changed, 17 insertions, 16 deletions
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 436375da80..3bc93d9743 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -2981,10 +2981,10 @@ C<STDERR> using various methods: print STDOUT "stdout 2\n"; print STDERR "stderr 2\n"; -If you specify C<< '<&=X' >>, where C<X> is a number or a filehandle, -then Perl will do an equivalent of C's C<fdopen> of that file -descriptor (and not call L<dup(2)>); this is more parsimonious -of file descriptors. For example: +If you specify C<< '<&=X' >>, where C<X> is a file descriptor number +or a filehandle, then Perl will do an equivalent of C's C<fdopen> of +that file descriptor (and not call L<dup(2)>); this is more +parsimonious of file descriptors. For example: # open for input, reusing the fileno of $fd open(FILEHANDLE, "<&=$fd") @@ -3002,18 +3002,19 @@ or open(FH, ">>&=OLDFH") -Being parsimonious on filehandles is useful (besides being -parsimonious) also for example when something is dependent -on the file descriptors, like for example locking using flock(). -If you do just a C<< open(A, '>>&B') >>, the filehandle A will not -have the file descriptor as B has, and therefore flock(A) will -not flock(B), and vice versa. But with C<< open(A, '>>&=B') >> -the filehandles will share the same file descriptor. - -Note that if Perl is using the standard C libraries' fdopen() then on -many UNIX systems, fdopen() is known to fail when file descriptors -exceed a certain value, typically 255. If you need more file -descriptors than that, consider rebuilding Perl to use the C<PerlIO>. +Being parsimonious on filehandles is also useful (besides being +parsimonious) for example when something is dependent on file +descriptors, like for example locking using flock(). If you do just +C<< open(A, '>>&B') >>, the filehandle A will not have the same file +descriptor as B, and therefore flock(A) will not flock(B), and vice +versa. But with C<< open(A, '>>&=B') >> the filehandles will share +the same file descriptor. + +Note that if you are using Perls older than 5.8.0, Perl will be using +the standard C libraries' fdopen() to implement the "=" functionality. +On many UNIX systems fdopen() fails when file descriptors exceed a +certain value, typically 255. For Perls 5.8.0 and later, PerlIO is +most often the default. You can see whether Perl has been compiled with PerlIO or not by running C<perl -V> and looking for C<useperlio=> line. If C<useperlio> |