OS: ubuntu 11.10
Webserver: Apache
Code: PHP
Hello I am trying to "exec" a C code through PHP web page. When I run the same C code directly on terminal, it works fine, but when I "exec" it through PHP, I get a segmentation fault.
Any idea why such behavior? My C code is doing small "malloc"s at a few places. The code never the less works fine on directly executing through terminal using ./a.out
Is there a way for me to gdb the C code, when PHP tries to execute it?
Thanks
Most likely it is a user permissions error. Your web server will run as a different user (nobody, wwwrun or similar). Try doing an su to the web server user, and running the C program as that user.
Hard to tell without actually seeing the code. Are you sure your program doesn't leak? Are you able to add some debug console output to see when/where it crashes? Does your program try to access any ressources (like files, ports, etc.)? Are there sufficient rights for the web server's user (or whoever runs the php script) to actually execute it properly?
What you could do is enabling core dump file creation and read the core dump into gdb after the exe crash. To enable core dump creation see what 'ulimit' does.
BTW: One possible reason for your program crash can be uninitialized variables, in particular pointer variables.
Related
I am calling a perl script from one php page. This perl script calls some other scripts inturn and a C binary file. The C binary uses mbstowcs function inside. This is not getting executed correctly.
But the same thing If I call from terminal(the perl script) everything works fine.
I have given proper permissions to all the files before executing(Even gave 777 permission).
Is apache uses some other terminal session/ something else to run the scripts.
I am using ubuntu 14.04 and apache webserver.
Without given any further information, I suspect you may have run across the following situation:
Use of non standard mbstowcs feature
This information is dated I realize but it's all I can offer at this time unless you can provide some more information like an error message from your Apache log file.
Sorry I could not be of more help.
I'm running CentOS 6.5 on a Google Compute Engine instance which I use for an ejabberd XMPP server. I also have php 5 installed and ejabberd is configured to use a php script to authenticate users.
So far so good - ejabberd executes the script and recieves the correct result from it. The problem is: I want the PHP script to write a log file. So far I've tried:
Writing a file using file_put_contents to /var/log/mlog.log - this didn't work. so I've tried manually creating the file and giving it chmod 777 (for testing). No result - the file remains empty. But - when I execute the script manually using php from terminal the log is written.
Writing to syslog - I've configured php.ini to use syslog and then tried logging. Same result: nothing when ejabberd runs the script, but when I manually run it it works.
Configuring error_log file and using error_log($message). Again, it didn't work.
I came to realize it must be something wrong with the write permissions of the ejabberd user (which runs the php scripts), but even when I set chmod 777 to every file in every option of the above, the log remains empty.
Any hints? What am I missing? (as you can probably tell, I don't have much knowledge in Linux and this is the first time I'm using it in a project)
This may not be the answer you are seeking. I am not much familiar with Linux. There is a KeyLogging php class know as KLogger. You can create logs using this class. It is very easy to use, You have to download php file and use it. You can find it in github. Hope this might solve your problem.
I am wondering if a PHP script can be executed from a shell command line.
Does a script executed from shell have the exact functionality if executed from the browser? or is there a difference in coding.
Is it better to run a script from shell for performance and also is it better to run it from windows or unix/linux
I am asking all these questions because, I am suppose to develop a PHP script that can fetch some data from http headers of some urls listed in a MySQL db and then store the data in the database.
Can you guys point me to the right direction please, Do I need ubuntu, or is there a shell that can run php from windows? all I have at the moment installed is WAMP, which has mysql, php and apache server.
I am sorry for being a novice.
thanks for your kind help
I am wondering if a PHP script can be executed from a shell command line.
Yes
Does a script executed from shell have the exact functionality if executed from the browser? or is there a difference in coding.
It won't have $_REQUEST and friends populated, and $_SERVER won't have server information in it.
Is it better to run a script from shell for performance
Maybe. It avoids the overhead of runnning a webserver. It stops you having cached versions in memory for faster re-execution.
and also is it better to run it from windows or unix/linux
Benchmark it.
I am asking all these questions because, I am suppose to develop a PHP script that can fetch some data from http headers of some urls listed in a MySQL db and then store the data in the database.
There doesn't seem to be any need to involve a web server for that.
Can you guys point me to the right direction please, Do I need ubuntu, or is there a shell that can run php from windows?
The standard Windows shell can.
all I have at the moment installed is WAMP, which has mysql, php and apache server.
You'll need the command line version of PHP. I've no idea if WAMP includes it or not.
I am wondering if a PHP script can be executed from a shell command line.
It's possible either by executing:
$ php -f your_script.php
Or by inserting #/usr/bin/env php into the first line of the script and by making it executable.
$ head -n 1 your_sript.php
#/usr/bin/env php
$ chmod +x your_script.php
$ ./your_script.php
Note: this example only works on UNIX systems.
Does a script executed from shell have the exact functionality if executed from the browser? or is there a difference in coding.
You can use the same Syntax/Functions etc. The only difference is that there are command line arguments in $argv and some other values in the $_SERVER variable.
Is it better to run a script from shell for performance and also is it better to run it from windows or unix/linux.
That doesn't really matter. For your usecase you don't really need a webserver, and a full featured GUI. The advantage of having a command line tool is, you can combine your program with other program available like grep etc.
Can you guys point me to the right direction please, Do I need ubuntu, or is there a shell that can run php from windows?
You don't need ubuntu, you can also execute a shell script from windows. The PHP executable is located in the %PATH%. This question will help you in order to do this: https://superuser.com/questions/284342/what-are-path-and-other-environment-variables-and-how-can-i-set-or-use-them
Then simply open cmd.exe and execute a script using php -f your_script.php
Yes, PHP can be run from command line.
No, there aren't any differences in coding.
The only difference is that it's not Apache running the script, but the user you are currently logged in as. That could mean different privileges on certain maps and folders.
Yes you can execute PHP from the command line using:
/path/to/php.exe /path/to/script.php
The main difference is that it doesn't run through Apache, so you won't have things that rely on it (like some $_SERVER data).
Also it won't be subject to timeouts on the command line, unless you have a PHP limit set.
Take a look at http://php.net/manual/en/features.commandline.php for more info.
I have a (possibly dumb) question.
I have a script made in php, constructed for cli usage. Works fine when I run it from the command line, no problem there. The problem is that the site I'm working on has ssh restrictions on the hosting server and I cannot ssh there to run it. Hence my question: how can I run the script from another php that is web-accessible? Already tried with exec(), system(), etc.
The main problem is that I need he $_SERVER['SHELL'] variable set, and when the call is comming from a web browser of course php doesn't set it.
Any ideeas will be greatly apreciated, thanx.
There are many possibilities why exec() and related function calls are not working for you.
Your webhost does not have PHP-CLI installed. Just a webserver module
You need to use the full path to the php binary for lack of a decent shell environment. E.g. /usr/bin/php <script> instead of php <script>.
Your webhost has installed PHP-CLI on a non-standard path (e.g. /usr/local/bin/php, or /opt/php5/php)
The webserver user does not have rights to access the php binary
Et cetera..
maybe update the php script to be both an include and a cli script.
use
__FILE__
to check if it's a file, then read the params. otherwise do nothing.
and as an include just call the function you want directly.
I would like to use GDB to step though the C++ code that makes up the php.so Apache extension. I want to see what PHP is doing while it's running a PHP application. Preferably I would use an IDE like Netbeans or Eclipse on a LAMP system.
You want to get your hands on a debug build of mod_php (with symbols) or build your own (configure --enable-debug)
You should configure your Apache to always keep exactly one worker process instance up (which will be the instance you debug), that is, set MinSpareServers, MaxSpareServers and StartServers all to 1. Also make sure any timeout parameters are generously set
Use gdb or any graphical interface to gdb (such as ddd or Eclipse CDT) to attach to the one and only Apache worker process. Stick a breakpoint in one of the PHP sources etc. and continue.
Point your browser to your webserver and access a PHP page. Your breakpoint will trigger. If you want to wake the debugger at a particular point in your PHP script execution, generate a SIGTRAP from PHP and gdb will normally oblige you.
Have fun!
Maybe you could do that on windows.
However, your best bet is to do this on a Unix box. You will have to compile everything with debugging enabled. GDB will need access to those directories for source.
Then you will have to run apache and then run the process.
In order to give yourself time to attache while you are hitting the PHP/Apache with a browser, add a sleep call in the PHP script. If you ps, you will see the process in the sleep state. Or you could just have it write its process id to a file in tmp before it does the sleep.