PHP Manual: popen

Description

resource popen ( string command, string mode )

Opens a pipe to a process executed by forking the command given by command.

Returns a file pointer identical to that returned by fopen(), except that it is unidirectional (may only be used for reading or writing) and must be closed with pclose(). This pointer may be used with fgets(), fgetss(), and fwrite().

If an error occurs, returns FALSE.

Note: If you're looking for bi-directional support (two-way), use proc_open().

Example 1. popen() example

<?php
$handle = popen("/bin/ls", "r");
?>

If the command to be executed could not be found, a valid resource is returned. This may seem odd, but makes sense; it allows you to access any error message returned by the shell:

<?php
error_reporting(E_ALL);

/* Add redirection so we can get stderr. */
$handle = popen('/path/to/spooge 2>&1', 'r');
echo "'$handle'; " . gettype($handle) . "\n";
$read = fread($handle, 2096);
echo $read;
pclose($handle);
?>

Note: When safe mode is enabled, you can only execute executables within the safe_mode_exec_dir. For practical reasons it is currently not allowed to have .. components in the path to the executable.

Warning

With safe mode enabled, the command string is escaped with escapeshellcmd(). Thus, echo y | echo x becomes echo y \| echo x.

See also pclose(), fopen(), and proc_open().