Regarding the return value:
"Returns the termination status of the process that was run. In case of an error then -1 is returned. "
and the note about the exit status: "pclose() is internally implemented using the waitpid(3) system call. To obtain the real exit status code the pcntl_wexitstatus() function should be used."
The documentation of the return value is, at best, misleading. The function returns, as does proc_close():
* -1 on error,
* WEXITSTATUS(status) if WIFEXITED(status) is true, or
* status if WIFEXITED(status) is false,
where status is the status parameter of waitpid().
This makes it impossible to differentiate between a relatively normal exit or a termination by signal, and reduces the value of the proc_close return code to a binary one (ok / something broke).
This can be seen in proc_open_rsrc_dtor() in ext/standard/proc_open.c (PHP 5.4.44, 5.6.12).
The note advising the use of pcntl_wexitstatus is plain wrong. One cannot use pcntl_wexitstatus because it already has been used.
pclose
(PHP 4, PHP 5, PHP 7, PHP 8)
pclose — Closes process file pointer
Parameters
-
handle -
The file pointer must be valid, and must have been returned by a successful call to popen().
Return Values
Returns the termination status of the process that was run. In case of
an error then -1 is returned.
Note:
If PHP has been compiled with --enable-sigchild, the return value of this function is undefined.
Examples
Example #1 pclose() example
<?php
$handle = popen('/bin/ls', 'r');
pclose($handle);
?>Notes
Note: Unix Only:
pclose() is internally implemented using the
waitpid(3)system call. To obtain the real exit status code the pcntl_wexitstatus() function should be used.
add a note
User Contributed Notes 4 notes
Uwe Ohse ¶
9 years ago
vdweij at mailsurf dot com ¶
21 years ago
As I understand pclose will return 0 (on every platform) in case popen could not execute the specified command.
Since popen only returns the status wether it was able to send a command and not wether it was succesfully executed. Only the returned value of pclose can be used to check wether a command could be executed.
Mike ¶
16 years ago
The termination status, as pointed out in another note, is not the same as the exit status from the process. However, something like "pclose($fp)/256" is not the correct way to extract the exit status, since this uses system- and version-specific knowledge of where in the termination status the exit status is stored. (Also, the process may not even have exited normally, so it may not have an exit status at all.)
Instead, the functions pcntl_wifexited() and pcntl_wexitstatus() should be used. They are wrappers for the C macros WIFEXITED() and WEXITSTATUS() that are designed for determining whether the process had an exit status and what that status was, respectively.
kcross at nssolutions dot com ¶
21 years ago
Somewhere between 4.1.1 and 4.2.3, the return value from pclose changed.
The exit status used to be in the second byte, so that the status would be (pclose($fp)/256).
It is now in the low-order byte, so the status is just pclose($fp).
Be careful.
