PHP exec vs system vs passthru

Question

What are the differences   Is there a specific situation or reason for each function  If yes  can you give some examples of those situations   PHP net says that they are used to execute external programs  see reference From the examples I see  I don t see any obvious difference   If I were to simply run a script  bash or python   which function do you recommend me to use

User · Answer

As drawn from  http   php net   amp  amp  Chipmunkninja      The system   Function      The system function in PHP takes a string argument with the command to   execute as well as any arguments you wish passed to that command  This   function executes the specified command  and dumps any resulting text   to the output stream  either the HTTP output in a web server   situation  or the console if you are running PHP as a command line   tool   The return of this function is the last line of output from the   program  if it emits text output       The exec   Function      The system function is quite useful and powerful  but one of the   biggest problems with it is that all resulting text from the program   goes directly to the output stream  There will be situations where you   might like to format the resulting text and display it in some   different way  or not display it at all       For this  the exec function in PHP is perfectly adapted  Instead of   automatically dumping all text generated by the program being executed   to the output stream  it gives you the opportunity to put this text in   an array returned in the second parameter to the function       The shell exec   Function      Most of the programs we have been executing thus far have been  more   or less  real programs1  However  the environment in which Windows and   Unix users operate is actually much richer than this  Windows users   have the option of using the Windows Command Prompt program  cmd exe   This program is known as a command shell       The passthru   Function      One fascinating function that PHP provides similar to those we have   seen so far is the passthru function  This function  like the others    executes the program you tell it to  However  it then proceeds to   immediately send the raw output from this program to the output stream   with which PHP is currently working  i e  either HTTP in a web server   scenario  or the shell in a command line version of PHP        The proc open   Function and popen     function      proc open   is similar to popen   but provides a much greater degree   of control over the program execution  cmd is the command to be   executed by the shell  descriptorspec is an indexed array where the   key represents the descriptor number and the value represents how PHP   will pass that descriptor to the child process  pipes will be set to   an indexed array of file pointers that correspond to PHP s end of any   pipes that are created  The return value is a resource representing   the process  you should free it using proc close   when you are   finished with it

User · Answer

It really all comes down to how you want to handle output that the command might return and whether you want your PHP script to wait for the callee program to finish or not    exec executes a command and passes output to the caller  or returns it in an optional variable   passthru is similar to the exec   function in that it executes a command   This function should be used in place of exec   or system   when the output from the Unix command is binary data which needs to be passed directly back to the browser  system executes an external program and displays the output  but only the last line    If you need to execute a command and have all the data from the command passed directly back without any interference  use the passthru   function

User · Answer

If you re running your PHP script from the command-line  passthru   has one large benefit   It will let you execute scripts programs such as vim  dialog  etc  letting those programs handle control and returning to your script only when they are done   If you use system   or exec   to execute those scripts programs  it simply won t work   Gotcha  For some reason  you can t execute less with passthru   in PHP

User · Answer

The previous answers seem all to be a little confusing or incomplete  so here is a table of the differences      ---------------- ----------------- ---------------- ----------------       Command       Displays Output   Can Get Output   Gets Exit Code    ---------------- ----------------- ---------------- ----------------    system           Yes  as text      Last line only   Yes                passthru         Yes  raw          No               Yes                exec             No                Yes  array       Yes                shell exec       No                Yes  string      No                 backticks        No                Yes  string      No                ---------------- ----------------- ---------------- ----------------      Displays Output  means it streams the output to the browser  or command line output if running from a command line    Can Get Output  means you can get the output of the command and assign it to a PHP variable  The  exit code  is a special value returned by the command  also called the  return status    Zero usually means it was successful  other values are usually error codes    Other misc things to be aware of    The shell exec   and the backticks operator do the same thing  There are also proc open   and popen   which allow you to interactively read write streams with an executing command  Add  2  amp 1  to the command string if you also want to capture display error messages   Use escapeshellcmd   to escape command arguments that may contain problem characters  If passing an  output variable to exec   to store the output  if  output isn t empty  it will append the new output to it   So you may need to unset  output  first

User · Answer

They have slightly different purposes    exec   is for calling a system command  and perhaps dealing with the output yourself    system   is for executing a system command and immediately displaying the output - presumably text    passthru   is for executing a system command which you wish the raw return from - presumably something binary    Regardless  I suggest you not use any of them  They all produce highly unportable code

[php] PHP exec() vs system() vs passthru()

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