Posts Tagged ‘exec’

Windows how to check which process locks file command – A M$ Windows equivalent of lsof command

Monday, February 23rd, 2015


I've had a task today to deploy a new WAR (Web Application Archive) Tomcat file on Apache Tomcat server running  on Windows server 2008 R2 UAT environment.
The client Tomcat application within war is providing a frontend to an proprietary Risk Analysis application called Risiko Management (developed by a German vendor called Schleupen).
The update of WAR file was part of a version upgrade of application so, both "Risk Analysis" desktop standalone server RiskKit and the Web frontend was developed by Schleupen had to be updated.
In order to update I followed the usual .WAR Tomcat Javafile upadate Tomcat process.

1. Stopped Tomcat running service Instance via services.msc command e.g.

Start (menu) -> Run




2. Move (by Renaming) old risk-analysis.war to risk-analysis_backup_2015.war

and also rename the automatically Tomcat extracted folder (named same name as the WAR archive file directory – D:\web\Apache-Tomcat-7.0.33\webapps\Risiko-Analysis\ to :\web\Apache-Tomcat-7.0.33\webapps\Risiko-Analysis_backup_2015, i.e. run:

C:\Users\risk-analysis> D:
D:\> CD \Web\Apache-Tomcat-7.0.33\webapps\

D:\Web\Apache-Tomcat-7.0.33\webapps> move risk-analysis.war risk-analysis_2015.war
D:\Web\Apache-Tomcat-7.0.33\webapps> move  
Risiko-Analysis\  Risiko-Analysis_backup_2015\

But unfortunately I couldn't rename it and I got below error:


Also I tried copying it using Windows Explorer Copy / Paste but this didn't worked either, and I got below error :


3. Finding what Locks a directory or File on M$ Windows

Obviously, the reason for unable to copy the directory was something was locking it. Actually there are plenty of locked files many running applications like Explorer do. A good example for all time locked file is Windows (swap file) pagefile.sys – this is Windows Linux equivalent of swap filesystem (enabled / disabled with spapon / swapoff commands)

Having the directory locked was a strange problem, because the Tomcat process was not running as I checked closely both in Windows taskmgr GUI interface and manually grepped for the process with tasklist command like so:


d:\>tasklist /m|find /i "tomcat"

tomcat7.exe                   4396 ntdll.dll, kernel32.dll, KERNELBASE.dll,

For people like me who use primary Linux , above command shows you very precious debugging information, it shows which Windows libraries (DLL) are loaded in memory and used by the process 


(Note that when Tomcat is running, it is visible with command)

D:\> wmic.exe process list brief | find /i "tomcat"
526          tomcat7.exe          8         4396       49           156569600

Just for those wondering the 156569600 number is number of bytes loaded in Windows memory used by Tomcat.

After tomcat was stopped above command returned empty string meaning obviously that tomcat is stopped ..

BTW, wmic command is very useful to get a list of process names (to list all running processes):

 D:> wmic.exe process list brief


Well obviously something was locking this directory (some of its subdirectories or a file name within the directory / folder), so I couldn't rename it just like that.
In Linux finding which daemon (service) is locking a file is pretty easy with lsof command (for those new to lsof check my previous article how to how to check what process listens on network port in Linux), however it was unknown to me how I can check which running service is locking a file and did a quick google search which pointed me to the famous handle part of SysInternals tools.
The command tool Handle.exe was exactly what I was looking for. 


To get list of all opened (locked) files and see which application has opened it just exec command without arguments, you will get
plenty of useful info which will help you to better understand what Windows OS is doing invisible in the background and what app uses what.


handle is pretty much Windows equivalent command of Linux lsof

To get which file was locked by Tomcat I used handle in conjuntion with find /i command which is pretty much like Linux's grep equivalent


C:\TEMP> Handle.exe | FIND /I "Tomcat"
   1C: File  (RW-)   D:\Web\Apache-Tomcat-7.0.33\webapps\Risk-Analysis\images\app

Alternatively if you have sysinternals and prefer GUI environment you can use SysInternals Process Explorer (press CTRL + F) and look for a string:


Next to handle I found also another GUI program (Internet Explorer extension) WhoLockMe, that can be used to show you all running programs and locked files by this programs.
WhoLockMe is pretty straight forward to use, though it shows GUI output you have to run the command from cmd line. Below is sample output screenshot of wholockme.



To Install Wholockme 

Unzip "" in a directory (for exemple : "C:\Program Files\WhoLockMe")
Launch "Install.bat" or execute this Windows registry modification command :

regsvr32 "C:\Program Files\WhoLockMe\WhoLockMe.dll"

To Uninstall WhoLockMe – if you need to later:


Execute command :

regsvr32 /u "C:\Program Files\WhoLockMe\WhoLockMe.dll"

Reboot (Or Kill Explorer.exe).

Removes the "C:\Program Files\WhoLockMe" directory and its contents.

Probably there are other ways to find out what is locking a file or direcotry using powershell scripts or .bat (batch) scripting. If you know of other way using default Windows embedded commands, please share in comments.


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Find all hidden files in Linux, Delete, Copy, Move all hidden files

Tuesday, April 15th, 2014

Listing hidden files is one of the common thing to do as sys admin. Doing manipulations with hidden files like copy / delete / move is very rare but still sometimes necessary here is how to do all this.

1. Find and show (only) all hidden files in current directory

find . -iname '.*' -maxdepth 1

maxdepth – makes files show only in 1 directory depth (only in current directory), for instance to list files in 2 subdirectories use -maxdepth 3 etc.

echo .*;

Yeah if you're Linux newbie it is useful to know echo command can be used instead of ls.
echo * command is very useful on systems with missing ls (for example if you mistakenly deleted it 🙂 )

2. Find and show (only) all hidden directories, sub-directories in current directory

To list all directories use cmd:

find /path/to/destination/ -iname ".*" -maxdepth 1 -type d

3. Log found hidden files / directories

find . -iname ".*" -maxdept 1 -type f | tee -a hidden_files.log

find . -iname ".*" -maxdepth 1 type d | tee -a hidden_directories.log
4. Delete all hidden files in current directory

cd /somedirectory
find . -iname ".*" -maxdepth 1 -type f -delete

5. Delete all hidden files in current directory

cd /somedirectory
find . -iname ".*" -maxdepth 1 -type d -delete

6. Copy all hidden files from current directory to other "backup" dir

find . -iname ".*" -maxdepth 1 -type f -exec cp -rpf '{}' directory-to-copy-to/ ;

7. Copy and move all hidden sub-directories from current directory to other "backup" dir

find . -iname ".*" -maxdepth 1 -type d -exec cp -rpf '{}' directory-to-copy-to/ ;

– Moving all hidden sub-directories from current directory to backup dir

find . -iname ".*" -maxdepth 1 -type d -exec mv '{}' directory-to-copy-to/ ;


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Linux: How to change recursively directory permissions to executable (+x) flag

Monday, September 2nd, 2013

change recursively permissions of directories and subdirectories Linux and Unix with find command
I had to copy large directory from one Linux server to windows host via SFTP proto (with WinSCP). However some of directories to be copied lacked executable flag, thus WinSCP failed to list and copy them.

Therefore I needed way to set recursively, all sub-directories under directory /mirror (located on Linux server) to +x executable flag.

There are two ways to do that one is directly through find cmd, second by using find with xargs
Here is how to do it with find:

# find /mirror -type d -exec chmod 755 {} + Same done with find + xargs:

# find /path/to/base/dir -type d -print0 | xargs -0 chmod 755
To change permissions only to all files under /mirror server directory with find

# find /path/to/base/dir -type f -exec chmod 644 {} +

Same done with find + xargs:
# find /path/to/base/dir -type f -print0 | xargs -0 chmod 644

Also, tiny shell script that recursively changes directories permissions ( is here

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Linux PHP Disable chmod() and chown() functions for better Apache server security

Monday, July 15th, 2013

I have to administer few inherited Linux servers with Ubuntu and Debian Linux. The servers hosts mainly websites with regularly un-updated Joomlas and some custom developed websites which were developed pretty unsecure. To mitigate hacked websites I already disabled some of most insecure functions like system(); eval etc. – I followed literally my previous tutorial PHP Webhosting security disable exec();, system();, open(); and eval();
Still in logs I see shits like:

[error] [client] PHP Warning:  mkdir(): No such file or directory in /var/www/site/plugins/system/jfdatabase/intercept.jdatabasemysql.php on line 161

Hence to prevent PHP mkdir(); and chown(); functiosn being active, I had to turn on in /etc/php5/apache2/php.ini – safe_mode . For some reason whoever configured Apache leave it off.

safe_mode = on

Hopefully by disabling this functions will keep cracker bot scripts to not create some weird directory structures on HDD or use it as mean to DoS overflow servers filesystem.

Hope this help others stabilize their servers too. Enjoy ! 🙂

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PHP: Better Webhosting Security – Disable exec(), exec_shell(), system(), popen(), eval() … shell fork functions

Sunday, June 23rd, 2013

increase php security better php security by disabling fork shell system and eval functions

If you work as System Administrator of WebHosting company, you definitely know how often it is that some automated cracker scripts (working as worms) intrude through buggy old crappy custom coded sites or unupdated obsolete Joomla / WordPress etc. installs. and run themselves trying to harvest for other vulnerable hosts. By default PHP enables running commands via shell with PHP functions like exec();, shell_exec(); , system();. and those script kiddie scripts use mainly this functions to spawn shell via vulnerable PHP app. Then scripts use whether php curl support is installed (i.e. php5-curl) to download and replicate itself to next vulnerable hop.

With that said it is a must after installing new Linux based server for hosting to disable this functions, to save yourself from future hassles …
Earlier, I blogged how to disable PHP system system(); and exec(); functions to raise Apache security using suhosin however this method requires php suhosin being used.

Yesterday, I had to configure new web hosting server with Debian 7, so I tried installing suhosin to use it to protect PHP from having enabled dangerous system();, eval(); exec(); .
I remember disabling system(); using suhosin php extension was working fine on older Debian releases, however in Debian 6.0, php5-suhosin package was causing severe Apache crashes and probably that's why in latest Debian Wheezy 7.0, php suhosin extension is no longer available. Therefore using suhosin method to disable system();, exec(); and other fork functions is no longer possible in Debian.

Since, suhosin is no longer there, I decided to use conventional PHP method via php.ini.

Here is how to do it



debian:~# vim /etc/php5/apache2/php.ini
And near end of file placed:

disable_functions =exec,passthru,shell_exec,system,proc_open,
popen,curl_exec, curl_multi_exec,parse_ini_file,show_source

allow_url_fopen Off
allow_url_include Off

It is good to explain few of above functions – shell_exec, proc_open, popen, allow_url_fopen,show_source  and allow_url_include.

Disabling shell_exec – disables from PHP scripts executing commands with bash slash ` `, i.e. `ls`. proc_open and popen allows reading files from file system.

show_source – makes possible also reading other PHP source files or can be used to display content of other files from fs.

To read newly placed config vars in php.ini usual apache restart is necessary:

debian:~# /etc/init.d/apache2 restart
[….] Restarting web server: apache2
. ok

Further on tо test whether system();, exec();, passthru(); … etc. are disabled. Make new PHP file with content:

$disabled_functions = ini_get('disable_functions');
if ($disabled_functions!='')
    $arr = explode(',', $disabled_functions);
    echo 'Disabled Functions:
    for ($i=0; $i<count($arr); $i++)
        echo $i.' - '.$arr[$i].'<br />';
    echo 'No functions disabled';

php show disabled functions screenshot improve php security by disabling shell spawn functions

Copy of above source code show_disabled_php_functions.php is here for download
. To test your Apache PHP configuration disabled functions download it with wget or curl and rename it to .php:

# cd /var/www # wget -q
mv show_disabled_php_functions.php.txt show_disabled_php_functions.php

After disabling functions on those newly setup Debian hosting Apache webserver, I remembered, same functions were still active on another CentOS Linux server.

To disable it there as well, had to edit:


[root@centos:~]# vim /etc/php.ini

And again place after last file line;

disable_functions =exec,passthru,shell_exec,system,proc_open,popen,
curl_exec, curl_multi_exec,parse_ini_file,show_source

allow_url_fopen Off
allow_url_include Off

Finally on CentOS host, had to restart Apache:

[root@centos:~]# /etc/init.d/httpd restart

For Security paranoids, there are plenty of other PHP functions to disable including, basic functions like ln, mv, mkdir, cp, cat etc.

Below is list of all functions to disable – only disable this whether you you're a PHP security freak and you're 100% some server hosted website will not use it:

disable_functions = "ln, cat, popen, pclose, posix_getpwuid, posix_getgrgid, posix_kill, parse_perms, system, dl, passthru, exec, shell_exec, popen, proc_close, proc_get_status, proc_nice, proc_open, escapeshellcmd, escapeshellarg, show_source, posix_mkfifo, mysql_list_dbs, get_current_user, getmyuid, pconnect, link, symlink, pcntl_exec, ini_alter, pfsockopen, leak, apache_child_terminate, posix_kill, posix_setpgid, posix_setsid, posix_setuid, proc_terminate, syslog, fpassthru, stream_select, socket_select, socket_create, socket_create_listen, socket_create_pair, socket_listen, socket_accept, socket_bind, socket_strerror, pcntl_fork, pcntl_signal, pcntl_waitpid, pcntl_wexitstatus, pcntl_wifexited, pcntl_wifsignaled, pcntl_wifstopped, pcntl_wstopsig, pcntl_wtermsig, openlog, apache_get_modules, apache_get_version, apache_getenv, apache_note, apache_setenv, virtual, chmod, file_upload, delete, deleted, edit, fwrite, cmd, rename, unlink, mkdir, mv, touch, cp, cd, pico"

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Linux: Convert recursively files content from WINDOWS-CP1251 to Unicode UTF-8 with recode and iconv

Wednesday, January 9th, 2013


Linux How to make mass file convert of charset windows CP1251 toutf8 and to other encodings

Some time ago I've written a tiny article, explaining how converting of HTML or TEXT file content inside file can be converted with iconv.

Just recently, I've made mirror of a whole website with its directory structure with wget cmd. The website to be mirrored was encoded with charset Windows-1251 (which is now a bit obsolete and not very recommended to use), where my Apache Webserver to which I mirrored is configured by default to deliver file content (.html, txt, js, css …) in newer and more standard (universal cyrillic) compliant UTF-8 encoding. Thus opening in browser from my website, the website was delivered in UTF-8, whether the file content itself was with encoding Windows CP-1251; Thus I ended up seeing a lot of monkey unreadable characters instead of Slavonic letters. To deal with the inconvenience, I've used one liner script that converts all Windows-1251 charset files to UTF-8. This triggered me writting this little post, hoping the info might be useful to others in a similar situation to mine:

1. Make Mass file charset / encoding convertion with recode

On most Linux hosts, recode is probably not installed. If you're on Debian / Ubuntu Linux install it with apt;

apt-get install --yes recode

It is also installable from default repositories on Fedora, RHEL, CentOS with:


yum -y install recode

Here is recode description taken from man page:

       recode – converts files between character sets

find . -name "*.html" -exec recode WINDOWS-1251..UTF-8 {} \;

If you have few file extensions whose chracter encoding needs to be converted lets say .html, .htm and .php use cmd:

find . -name "*.html" -o -name '*.htm' -o -name '*.php' -exec recode WINDOWS-1251..UTF-8 {} \;

Btw I just recently learned how one can look for few, file extensions with find under one liner the argument to pass is -o -name '*.file-extension', as you can see from  example, you can look for as  many different file extensions as you like with one find search command.

After completing the convertion, I've remembered that earlier I've also used iconv on a couple of occasions to convert from Cyrillic CP-1251 to Cyrillic UTF-8, thus for those who prefer to complete convertion with iconv here is an alternative a bit longer method using for cycle + mv and iconv.

2. Mass file convertion with iconv

for i in $(find . -name "*.html" -print); do
iconv -f WINDOWS-1251 -t UTF-8 $i > $i.utf-8;
mv $i $i.bak;
mv $i.utf-8 $i;

As you see in above line of code, there are two occurances of move command as one is backupping all .html files and second mv overwrites with files with converted encoding. For any other files different from .html, just change in cmd find . -iname '*.html' to whatever file extension.

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Disabling PHP system(); and exec(); functions to raise up Apache security on Debian GNU / Linux

Wednesday, July 18th, 2012

Disabling PHP system(); and exec(); functions to raise up Apache security on Debian Gnu / Linux

At security critical hosts running Apache + PHP based sites it is recommended functions like:


to be disabled. The reason is to mainly harden against script kiddies who might exploit your site/s and upload some shitty SK tool like PHP WebShell, PHP Shell and the probably thousands of “hacker” variations that exist nowdays.

In latest Debian stable Squeeze, suhosinadvanced protection module for php5 is being installed and enabled in Apache (by default).
Simply disabling a number of functions using suhosin, could prevent multiple of future headaches and hours of pondering on who 0wn3d your server ….

Disabling the basic PHP system(); and other similar functions which allows shell spawn is not always possible, since some websites or CMS platforms depends on them for proper runnig, anyways whether it is possible disabling ’em is a must.
There are two ways to disable system(); functions; One is through using /etc/php5/apache2/conf.d/suhosin.ini and 2nd by adding a list of functions that has to be disabled directly in Website Virtualhost file or in apache2.conf (/etc/apache2/apache2.conf;
For people hosting multiple virtualhost websites on the same server using the custom domain Virtualhost method is probably better, since on a global scale the functions could be enabled if some of the websites hosted on the server requires exec(); to work OK. In any case using /etc/php5/apache2/conf.d/suhosin.ini to disable system(); functions in PHP is less messy …

1. Disabling PHP system(); fuctions through /etc/apache2/apache2.conf and custom site Vhosts

Place somewhere (I prefer near the end of config);;;

php_admin_flag safe_mode on
php_admin_value disable_functions "system, exec, shell_exec, passthru , ini_alter, dl, pfsockopen, openlog, syslog, readlink, symlink, link, leak, fsockopen, popen, escapeshellcmd, apache_child_terminate apache_get_modules, apache_get_version, apache_getenv, apache_note,apache_setenv,virtual"

Disabling it for custom virtualhost is done by simply adding above Apache directvies (before the closing tag in /etc/apache2/sites-enabled/

2. Disabling PHP system();, exec(); shell spawn with suhosin.ini

In /etc/php5/apache2/conf.d/suhosin.ini add;;

suhosin.executor.func.blacklist =system, exec, shell_exec, passthru, ini_alter, dl,
pfsockopen, openlog, syslog, readlink, symlink, link, leak, fsockopen, popen,
escapeshellcmd, apache_child_terminate apache_get_modules, apache_get_version,
apache_getenv, apache_note,apache_setenv,virtual

To do it directly via shell issue;;;

server: conf.d/# cd /etc/php5/apache2/conf.d/
server: conf.d# echo 'suhosin.executor.func.blacklist =system, exec, shell_exec, passthru, ini_alter, dl,' >> suhosin.ini
server: conf.d# echo 'pfsockopen, openlog, syslog, readlink, symlink, link, leak, fsockopen, popen,' >> suhosin.ini
server: conf.d# echo escapeshellcmd, apache_child_terminate apache_get_modules, apache_get_version,' >> suhosin.ini
server: conf.d# echo 'apache_getenv, apache_note,apache_setenv,virtual' >> suhosin.ini

Then to re-load the memory loaded Apache libphp library an Apache restart is necessary;

server: conf.d# /etc/init.d/apache2 restart
Restarting web server: apache2 ... waiting .
server: conf.d#

Tadam, this should be quite a good security against annoying automated script attacks. Cheers 😉

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How to check MASTER / SLAVE MySQL nodes status – Check MySQL Replication Status

Thursday, April 19th, 2012

I'm doing replication for one server. Its not the first time I do configure replication between two MySQL database nodes, however since I haven't done it for a few years, my "know how" has mostly vanished so I had some troubles in setting it up. Once I followed some steps to configure replication I had to check if the two MASTER / Slave MySQL db nodes communicate properly. Hence I decided to drop a short post on that just in case if someone has to do the same or if I myself forget how I did it so I can check later on:

1. Check if MASTER MySQL server node is configured properly

The standard way to check a MySQL master node status info is with:

mysql> show master status;
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
| mysql-bin.000007 | 106 | database1,database2,database3 | |
1 row in set (0.00 sec)

By putting \G some extra status info is provided:

mysql> show master status\G;
*************************** 1. row ***************************
File: mysql-bin.000007
Position: 106
Binlog_Do_DB: database1,database2,database3
1 row in set (0.00 sec)

No query specified

2. Check if Slave MySQL node is configured properly

To check status of the slave the cmd is:

mysql> show slave status;

The command returns an output like:

mysql> show slave status;+———————————-+————-+————-+————-+—————+——————+———————+————————-+—————+———————–+——————+——————-+——————————————————-+———————+——————–+————————+————————-+—————————–+————+————+————–+———————+—————–+—————–+—————-+—————+——————–+——————–+——————–+—————–+——————-+—————-+———————–+——————————-+—————+—————+—————-+—————-+| Slave_IO_State | Master_Host | Master_User | Master_Port | Connect_Retry | Master_Log_File | Read_Master_Log_Pos | Relay_Log_File | Relay_Log_Pos | Relay_Master_Log_File | Slave_IO_Running | Slave_SQL_Running | Replicate_Do_DB | Replicate_Ignore_DB | Replicate_Do_Table | Replicate_Ignore_Table | Replicate_Wild_Do_Table | Replicate_Wild_Ignore_Table | Last_Errno | Last_Error | Skip_Counter | Exec_Master_Log_Pos | Relay_Log_Space | Until_Condition | Until_Log_File | Until_Log_Pos | Master_SSL_Allowed | Master_SSL_CA_File | Master_SSL_CA_Path | Master_SSL_Cert | Master_SSL_Cipher | Master_SSL_Key | Seconds_Behind_Master | Master_SSL_Verify_Server_Cert | Last_IO_Errno | Last_IO_Error | Last_SQL_Errno | Last_SQL_Error |+———————————-+————-+————-+————-+—————+——————+———————+————————-+—————+———————–+——————+——————-+——————————————————-+———————+——————–+————————+————————-+—————————–+————+————+————–+———————+—————–+—————–+—————-+—————+——————–+——————–+——————–+—————–+——————-+—————-+———————–+——————————-+—————+—————+—————-+—————-+| Waiting for master to send event | HOST_NAME.COM | slave_user | 3306 | 10 | mysql-bin.000007 | 106 | mysqld-relay-bin.000002 | 251 | mysql-bin.000007 | Yes | Yes | database1,database2,database3 | | | | | | 0 | | 0 | 106 | 407 | None | | 0 | No | | | | | | 0 | No | 0 | | 0 | |+———————————-+————-+————-+————-+—————+——————+———————+————————-+—————+———————–+——————+——————-+——————————————————-+———————+——————–+————————+————————-+—————————–+————+————+————–+———————+—————–+—————–+—————-+—————+——————–+——————–+——————–+—————–+——————-+—————-+———————–+——————————-+—————+—————+—————-+—————-+

As you can see the output is not too readable, as there are too many columns and data to be displayed and this doesn't fit neither a text console nor a graphical terminal emulator.

To get more readable (more verbose) status for the SQL SLAVE, its better to use command:

mysql> show slave status\G;

Here is a sample returned output:

mysql> show slave status\G;*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: HOST_NAME.COM Master_User: slave_user Master_Port: 3306 Connect_Retry: 10 Master_Log_File: mysql-bin.000007 Read_Master_Log_Pos: 106 Relay_Log_File: mysqld-relay-bin.000002 Relay_Log_Pos: 251 Relay_Master_Log_File: mysql-bin.000007 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: database1,database2,database3 Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 106 Relay_Log_Space: 407 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: 1 row in set (0.00 sec)ERROR: No query specified

If show master status or shwo slave status commands didn't reveal replication issue, one needs to stare at the mysql log for more info.

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PHP system(); hide command output – How to hide displayed output with exec();

Saturday, April 7th, 2012

I've recently wanted to use PHP's embedded system(""); – external command execute function in order to use ls + wc to calculate the number of files stored in a directory. I know many would argue, this is not a good practice and from a performance view point it is absolutely bad idea. However as I was lazy to code ti in PHP, I used the below line of code to do the task:

echo "Hello, ";
$line_count = system("ls -1 /dir/|wc -l");
echo "File count in /dir is $line_count \n";

This example worked fine for me to calculate the number of files in my /dir, but unfortunately the execution output was also visialized in the browser. It seems this is some kind of default behaviour in both libphp and php cli. I didn't liked the behaviour so I checked online for a solution to prevent the system(); from printing its output.

What I found as a recommendations on many pages is instead of system(); to prevent command execution output one should use exec();.
Therefore I used instead of my above code:

echo "Hello, ";
$line_count = exec("ls -1 /dir/|wc -l");
echo "File count in /dir is $line_count \n";

By the way insetad of using exec();, it is also possible to just use ` (backtick) – in same way like in bash scripting's .

Hence the above code can be also written for short like this:

echo "Hello, ";
$line_count = `ls -1 /dir/|wc -l`;
echo "File count in /dir is $line_count \n";


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