From:
Operating system: Linux
PHP version: 5.3.3
Package: Filesystem function related
Bug Type: Bug
Bug description:Cannot open file descriptor streams
Description:
------------
PHP cannot open, read from, or write to arbitrary file descriptors, a
feature that is necessary for communications with certain utilities that
expect input or output on certain file descriptors. When programming in C,
this functionality is provided by fdopen(). A feature request was filed
over seven years ago for PHP to have a similar capability through the
php:// stream wrapper (#26158), but the bug was marked as bogus for no
adequately defined reason.
The alternative to being able to use a fdopen()-like function is to open
the file descriptor as a named file through /dev/fd/ or /proc/self/fd/.
This works in C using fopen("/dev/fd/<descriptor>", "w"), but it does not
work in PHP because PHP incorrectly attempts to dereference the
pseudo-symlink before opening it.
I have a C program and a PHP script that both attempt to do the same thing:
open file descriptor 3 for writing using /dev/fd/3, read until EOF from
standard in and write to the file descriptor. Both should be run as:
(executable) 3>&1 | cat
Test script:
---------------
PHP script:
<?php
$file = fopen("/dev/fd/3", "w");
if (!$file) exit(1);
$input = stream_get_contents(STDIN);
fwrite($file, $input);
fclose($file);
C program:
#include <stdio.h>
int main() {
char buf[8192];
int count;
FILE *file;
file = fopen("/dev/fd/3", "w");
if (file == NULL) {
perror("Opening /dev/fd/3");
return 1;
}
while ((count = fread(buf, 1, sizeof(buf), stdin)) > 0) {
fwrite(buf, count, 1, file);
if (feof(stdin)) break;
}
return 0;
}
Expected result:
----------------
Input should be mirrored to file descriptor 3; when called using the
command line above, it should be mirrored to standard output.
Actual result:
--------------
I get the following warning:
PHP Warning: fopen(/dev/fd/3): failed to open stream: No such file or
directory in test.php on line 2
An strace of the PHP process shows the incorrect behavior:
lstat("/dev/fd/3", {st_mode=S_IFLNK|0300, st_size=64, ...}) = 0
readlink("/dev/fd/3", "pipe:[637257]", 4096) = 13
lstat("/dev/fd/pipe:[637257]", 0x7fff76ae8140) = -1 ENOENT (No such file or
directory)
lstat("/dev/fd", {st_mode=S_IFLNK|0777, st_size=13, ...}) = 0
readlink("/dev/fd", "/proc/self/fd"..., 4096) = 13
lstat("/proc/self/fd", {st_mode=S_IFDIR|0500, st_size=0, ...}) = 0
lstat("/proc/self", {st_mode=S_IFLNK|0777, st_size=64, ...}) = 0
readlink("/proc/self", "28234"..., 4096) = 5
lstat("/proc/28234", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
lstat("/proc", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
open("/proc/28234/fd/pipe:[637257]", O_WRONLY|O_CREAT|O_TRUNC, 0666) = -1
ENOENT (No such file or directory)
--
Edit bug report at http://bugs.php.net/bug.php?id=53465&edit=1
--
Try a snapshot (PHP 5.2):
http://bugs.php.net/fix.php?id=53465&r=trysnapshot52
Try a snapshot (PHP 5.3):
http://bugs.php.net/fix.php?id=53465&r=trysnapshot53
Try a snapshot (trunk):
http://bugs.php.net/fix.php?id=53465&r=trysnapshottrunk
Fixed in SVN:
http://bugs.php.net/fix.php?id=53465&r=fixed
Fixed in SVN and need be documented:
http://bugs.php.net/fix.php?id=53465&r=needdocs
Fixed in release:
http://bugs.php.net/fix.php?id=53465&r=alreadyfixed
Need backtrace:
http://bugs.php.net/fix.php?id=53465&r=needtrace
Need Reproduce Script:
http://bugs.php.net/fix.php?id=53465&r=needscript
Try newer version:
http://bugs.php.net/fix.php?id=53465&r=oldversion
Not developer issue:
http://bugs.php.net/fix.php?id=53465&r=support
Expected behavior:
http://bugs.php.net/fix.php?id=53465&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=53465&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=53465&r=submittedtwice
register_globals:
http://bugs.php.net/fix.php?id=53465&r=globals
PHP 4 support discontinued: http://bugs.php.net/fix.php?id=53465&r=php4
Daylight Savings: http://bugs.php.net/fix.php?id=53465&r=dst
IIS Stability:
http://bugs.php.net/fix.php?id=53465&r=isapi
Install GNU Sed:
http://bugs.php.net/fix.php?id=53465&r=gnused
Floating point limitations:
http://bugs.php.net/fix.php?id=53465&r=float
No Zend Extensions:
http://bugs.php.net/fix.php?id=53465&r=nozend
MySQL Configuration Error:
http://bugs.php.net/fix.php?id=53465&r=mysqlcfg
