Program execution function Library: System

System

(PHP3, PHP4)

System---&http://www.aliyun.com/zixun/aggregation/37954.html ">NBSP; Execute an external program and display the output

Syntax: string system (String command [, int return_var])

Description:

System () executes the given command and outputs the result. If a parameter return_var is given, the status code that executes the command is written to the variable.

Note: If you allow data from user input to be passed to this function, you should use Escapeshellcmd () to determine that this user cannot spoof (trick) the system to execute arbitrary (arbitrary) commands.

Note: If you use this function to start a program and you want to leave it in the background (background), you must make sure that the output of the program is turned (redirected) to a file or some output stream, otherwise PHP will hang (hang) Until the program execution is finished.

If PHP is operating as a server module, System () will try to automatically clear the output buffer of the Web server after each row is output.

Success is returned to the last line of the command, and false is returned.

If you need to execute a command and get all the data from the command, you can use the PassThru () function.

Reference: EXEC () PassThru () Popen () Escapeshellcmd ()