ID: 15642
Updated by: [EMAIL PROTECTED]
Reported By: [EMAIL PROTECTED]
Status: Open
Bug Type: Program Execution
Operating System: Linux 2.2.18
PHP Version: 4.0.5
New Comment:
Just wanted to add this tip from the notes in the manual:
Here's a neat trick that exploits an inherent php anomaly... if you
want to
run a shell command but not have it take up two processes for the
entire
life of the command (a child for the shell and a grandchild for the
command), add a "&" at the end of the command to kill the
shell and leave the grandchild command running... Though it's a bit
counterintuitive, php will continue to listen for the orphanized
grandchild command's STDOUT as long as it continues to run, provided
STDOUT hasn't been been redirected with a ">/some/file"...
Very helpful if you're in a low-process-quota situation - I might even
go
so far as to say that this benefit might warrant ALWAYS using a
"&" in php Unix system command situations - though the
jury's still out on that one...
Derick
Previous Comments:
------------------------------------------------------------------------
[2002-02-20 04:20:00] [EMAIL PROTECTED]
Using CGI PHP 4.0.5 on Linux 2.2.18. Starting a "PHP shell script"
using the system function with
system("/tmp/demo.php &");
will hang the parent PHP until /tmp/demo.php finishes execution.
Replacing /tmp/demo.php with a shell script wrapper /tmp/demo.sh, which
does
#! /bin/sh --
env
lsof $$
php -q ... /tmp/demo.php
shows the shell script is inheriting open file handles from the parent
PHP. These handles include the session handler file handles, database
file handles and other file handles. These handles are being passed on
to the child php interpreter, where they are inaccessible except for
the dio_*() functions (fds with no PHP ressource associated).
Since the session handle will LOCK on these fds, the parent CGI will
hang until the child PHP completes execution.
Process traces are provided below.
We worked around the problem by writing a program closeme which closes
all file handles 3-63 before starting the PHP subprocess. The PHP
program execution functions system(), popen() and the like should do
this automatically.
Kristian
NB: I am not on the php-dev list any more. Please be sure to cc all
discussion to the address [EMAIL PROTECTED]
custsys:~ # lsof /tmp/sess_c8bf4bd82d100c7547aab62fcb9b36f4
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
php4 16569 wwwrun 4u REG 3,2 348 44835
/tmp/sess_c8bf4bd82d100c7547aab62fcb9b36f4
gewinnlis 16572 wwwrun 4u REG 3,2 348 44835
/tmp/sess_c8bf4bd82d100c7547aab62fcb9b36f4
custsys:~ #
wwwrun 16569 14188 0 10:13 ? 00:00:00 php4
wwwrun 16572 1 6 10:13 ? 00:00:02 php -q
/home/www/servers/server-with-no-name.de/php/batch/gewinnliste.php
lotterygewlst-20020
207-1312.csv 107 1 20.02.2002
custsys:~ # lsof -p 16572
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
gewinnlis 16572 wwwrun cwd DIR 3,5 211 15925
/home/www/servers/server-with-no-name.de/php/batch
gewinnlis 16572 wwwrun rtd DIR 3,2 370 2 /
gewinnlis 16572 wwwrun txt REG 3,2 2596986 26151
/usr/local/php4/bin/php
gewinnlis 16572 wwwrun mem REG 3,2 106242 4418
/lib/ld-2.2.so
gewinnlis 16572 wwwrun mem REG 3,2 14330 4427
/lib/libdl.so.2
gewinnlis 16572 wwwrun mem REG 3,2 228284 19650
/usr/lib/libmysqlclient.so.10.0.0
gewinnlis 16572 wwwrun mem REG 3,2 60858 19721
/usr/lib/libmcrypt.so.4.0.4
gewinnlis 16572 wwwrun mem REG 3,2 19173 25711
/usr/lib/libltdl.so.0.1.2
gewinnlis 16572 wwwrun mem REG 3,2 66669 4440
/lib/libresolv.so.2
gewinnlis 16572 wwwrun mem REG 3,2 186132 4428
/lib/libm.so.6
gewinnlis 16572 wwwrun mem REG 3,2 27143 4424
/lib/libcrypt.so.1
gewinnlis 16572 wwwrun mem REG 3,2 92252 4430
/lib/libnsl.so.1
gewinnlis 16572 wwwrun mem REG 3,2 1382179 4423
/lib/libc.so.6
gewinnlis 16572 wwwrun mem REG 3,2 63381 7759
/lib/libz.so.1.1.3
gewinnlis 16572 wwwrun mem REG 3,2 45878 4434
/lib/libnss_files.so.2
gewinnlis 16572 wwwrun 0r CHR 1,3 2511 /dev/null
gewinnlis 16572 wwwrun 1w REG 3,2 0 44860 /tmp/demo
gewinnlis 16572 wwwrun 2w REG 3,2 0 44840 /tmp/err
gewinnlis 16572 wwwrun 3u REG 3,2 0 40917
/var/state/httpd/mm.14186.sem
gewinnlis 16572 wwwrun 4u REG 3,2 348 44835
/tmp/sess_c8bf4bd82d100c7547aab62fcb9b36f4
gewinnlis 16572 wwwrun 5u sock 0,0 306704 can't identify
protocol
gewinnlis 16572 wwwrun 6u IPv4 306716 TCP
localhost:3755->localhost:mysql (ESTABLISHED)
gewinnlis 16572 wwwrun 7u IPv4 306718 TCP
custsys.nsz.netuse.de:3756->www.lottery-customer.de:mysql
(ESTABLISHED)
gewinnlis 16572 wwwrun 8r REG 3,5 7824333 16176
/home/custsys/import/lottery/gewinnliste/gewlst-20020207-1312.csv
custsys:~ #
custsys:~ # lsof -p 16569
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
php4 16569 wwwrun cwd DIR 3,5 78 14153
/home/www/servers/server-with-no-name.de/cgi
php4 16569 wwwrun rtd DIR 3,2 370 2 /
php4 16569 wwwrun txt REG 3,5 2641883 14154
/home/www/servers/server-with-no-name.de/cgi/php4
php4 16569 wwwrun mem REG 3,2 106242 4418 /lib/ld-2.2.so
php4 16569 wwwrun mem REG 3,2 14330 4427 /lib/libdl.so.2
php4 16569 wwwrun mem REG 3,2 228284 19650
/usr/lib/libmysqlclient.so.10.0.0
php4 16569 wwwrun mem REG 3,2 60858 19721
/usr/lib/libmcrypt.so.4.0.4
php4 16569 wwwrun mem REG 3,2 19173 25711
/usr/lib/libltdl.so.0.1.2
php4 16569 wwwrun mem REG 3,2 66669 4440
/lib/libresolv.so.2
php4 16569 wwwrun mem REG 3,2 186132 4428 /lib/libm.so.6
php4 16569 wwwrun mem REG 3,2 27143 4424
/lib/libcrypt.so.1
php4 16569 wwwrun mem REG 3,2 92252 4430
/lib/libnsl.so.1
php4 16569 wwwrun mem REG 3,2 205939 15746
/usr/lib/libssl.so.0.9.6
php4 16569 wwwrun mem REG 3,2 892057 15743
/usr/lib/libcrypto.so.0.9.6
php4 16569 wwwrun mem REG 3,2 1382179 4423 /lib/libc.so.6
php4 16569 wwwrun mem REG 3,2 63381 7759
/lib/libz.so.1.1.3
php4 16569 wwwrun 0r FIFO 0,0 306709 pipe
php4 16569 wwwrun 1w FIFO 0,0 306710 pipe
php4 16569 wwwrun 2w REG 3,5 2448931 14156
/home/www/servers/server-with-no-name.de/logs/error.log
php4 16569 wwwrun 3u REG 3,2 0 40917
/var/state/httpd/mm.14186.sem
php4 16569 wwwrun 4u REG 3,2 348 44835
/tmp/sess_c8bf4bd82d100c7547aab62fcb9b36f4
custsys:~ # strace -f -p 16569
flock(4, LOCK_EX <unfinished ...>
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=15642&edit=1
