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proc_open
Execute a command and open file pointers for input/output
Description
resourcefalse proc_open(
arraystring $command,
array $descriptor_spec,
array &$pipes,
stringnull $cwd = null,
arraynull $env_vars = null,
arraynull $options = null
)
Parameters
-
command
-
The commandline to execute as string. Special characters have to be properly escaped,
and proper quoting has to be applied.
Note:
On Windows, unless bypass_shell is set to true in
options, the command is
passed to cmd.exe (actually, %ComSpec%)
with the /c flag as unquoted string
(i.e. exactly as has been given to proc_open).
This can cause cmd.exe to remove enclosing quotes from
command (for details see the cmd.exe documentation),
resulting in unexpected, and potentially even dangerous behavior, because
cmd.exe error messages may contain (parts of) the passed
command (see example below).
As of PHP 7.4.0, command may be passed as array of command parameters.
In this case the process will be opened directly (without going through a shell)
and PHP will take care of any necessary argument escaping.
Note:
On Windows, the argument escaping of the array elements assumes that the
command line parsing of the executed command is compatible with the parsing
of command line arguments done by the VC runtime.
-
descriptor_spec
-
An indexed array where the key represents the descriptor number and the
value represents how PHP will pass that descriptor to the child
process. 0 is stdin, 1 is stdout, while 2 is stderr.
Each element can be:
- An array describing the pipe to pass to the process. The first
element is the descriptor type and the second element is an option for
the given type. Valid types are
pipe (the second
element is either r to pass the read end of the pipe
to the process, or w to pass the write end) and
file (the second element is a filename).
Note that anything else than w is treated like r.
-
A stream resource representing a real file descriptor (e.g. opened file,
a socket,
STDIN).
The file descriptor numbers are not limited to 0, 1 and 2 - you may
specify any valid file descriptor number and it will be passed to the
child process. This allows your script to interoperate with other
scripts that run as "co-processes". In particular, this is useful for
passing passphrases to programs like PGP, GPG and openssl in a more
secure manner. It is also useful for reading status information
provided by those programs on auxiliary file descriptors.
-
pipes
-
Will be set to an indexed array of file pointers that correspond to
PHP's end of any pipes that are created.
-
cwd
-
The initial working dir for the command. This must be an
absolute directory path, or null
if you want to use the default value (the working dir of the current
PHP process)
-
env_vars
-
An array with the environment variables for the command that will be
run, or null to use the same environment as the current PHP process
-
options
-
Allows you to specify additional options. Currently supported options
include:
-
suppress_errors (windows only): suppresses errors
generated by this function when it's set to true
-
bypass_shell (windows only): bypass
cmd.exe shell when set to true
-
blocking_pipes (windows only): force
blocking pipes when set to true
-
create_process_group (windows only): allow the
child process to handle CTRL events when set to true
-
create_new_console (windows only): the new process
has a new console, instead of inheriting its parent's console
Return Values
Returns a resource representing the process, which should be freed using
proc_close when you are finished with it. On failure
returns false.
Examples
Example #1 A proc_open example
<?php
$descriptorspec = array(
0 => array("pipe", "r"), // stdin is a pipe that the child will read from
1 => array("pipe", "w"), // stdout is a pipe that the child will write to
2 => array("file", "/tmp/error-output.txt", "a") // stderr is a file to write to
);
$cwd = '/tmp';
$env = array('some_option' => 'aeiou');
$process = proc_open('php', $descriptorspec, $pipes, $cwd, $env);
if (is_resource($process)) {
// $pipes now looks like this:
// 0 => writeable handle connected to child stdin
// 1 => readable handle connected to child stdout
// Any error output will be appended to /tmp/error-output.txt
fwrite($pipes[0], '<?php print_r($_ENV); ?>');
fclose($pipes[0]);
echo stream_get_contents($pipes[1]);
fclose($pipes[1]);
// It is important that you close any pipes before calling
// proc_close in order to avoid a deadlock
$return_value = proc_close($process);
echo "command returned $return_value\n";
}
?>
The above example will output
something similar to:
Array
(
[some_option] => aeiou
[PWD] => /tmp
[SHLVL] => 1
[_] => /usr/local/bin/php
)
command returned 0
Example #2 proc_open quirk on Windows
While one may expect the following program to search the file
filename.txt for the text search and
to print the results, it behaves rather differently.
<?php
$descriptorspec = [STDIN, STDOUT, STDOUT];
$cmd = '"findstr" "search" "filename.txt"';
$proc = proc_open($cmd, $descriptorspec, $pipes);
proc_close($proc);
?>
The above example will output:
'findstr" "search" "filename.txt' is not recognized as an internal or external command,
operable program or batch file.
To work around that behavior, it is usually sufficient to enclose the
command in additional quotes:
$cmd = '""findstr" "search" "filename.txt""';
Notes
Note:
Windows compatibility: Descriptors beyond 2 (stderr) are made available to
the child process as inheritable handles, but since the Windows
architecture does not associate file descriptor numbers with low-level
handles, the child process does not (yet) have a means of accessing those
handles. Stdin, stdout and stderr work as expected.
Note:
If you only need a uni-directional (one-way) process pipe, use
popen instead, as it is much easier to use.
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