Summary of usage of php external execution command function

This article mainly introduces the usage of PHP external execution command function, and analyzes the related usage skills of exec and system to execute external commands in the form of examples. Friends in need can refer to it

First of all, self-examination Yes, I have been studying and using PHP for more than a year, and I have been studying and using the Linux system for almost a year. I didn’t know that an interpreted language like PHP can directly call operating commands to control the system...

Let’s first summarize the operations of Linux. I won’t mention the commonly used cd, cp, mv, rm and the like. The first point worth summarizing is that ordinary users need to add before the command when extracting root permissions. Enter sudo, and then the command to output the line number in the vi editor is: set nu.
PHP’s built-in functions exec and system can call system commands (shell commands). However, if you want to use these two functions, the safe mode in php.ini must be turned off, otherwise PHP will not allow calling the system for security reasons. commanded.

Let’s first look at the explanation of these two functions in the PHP manual:

1. exec --- Execute external programs

Syntax: string exec (string command [, array &output [, int &return_var]] )

Description:

exec() executes the given command command, but It does not output anything, it simply returns the last line from the result of the command. If you need to execute a command and get all the data from the command, you can use the passthru() function.

If the parameter array is given, the specified array will be filled with each line output by the command. Note: If the array already contains some elements, exec() will append it to the array. later, if you don't want this function to append elements, you can call unset() before passing the array to exec().

2. system --- Execute the external program and display the output

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

Description:

system() executes the given command command and outputs the result. If the parameter return_var is given, the status code of the executed command will be written to this variable.

If PHP is running as a server module, system() will try to automatically clear the web server's output buffer after outputting each line. Returns the last line of the command on success, false on failure.

If you need to execute a command and obtain all information from the command, you can use the passthru() function.

Both of these are used to call system shell commands.

The difference:

exec can return all execution results to $output In the function (array), $status is the status of execution. 0 is success and 1 is failure.

systerm does not need to provide the $output function. It returns the result directly. Similarly, $return_var is the status code of execution. 0 is failure. Success 1 means failure

exec example:

The following is the quoted content:

<?php
  $a = exec("dir",$out,$status);
  print_r($a);
  print_r($out);
  print_r($status);
?>

system example:

The following is the quoted content:

<?php
  $a = system("dir",$out);
  print_r($a);
  print_r($out);
?>

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