How to solve php exec error problem

Solution to php exec error: 1. Modify the execution permission of ping or the corresponding command; 2. Complete the full path of the command with "exec('/usr/sbin',$output);"; 3. Add the target directory to the environment variables.

The operating environment of this article: Windows7 system, PHP7.1 version, DELL G3 computer

How to solve the php exec error problem?

The exec() function in PHP fails to execute system commands?

0. Description

In php, we can use exec() to execute system commands, but sometimes we encounter exec( )The command execution is unsuccessful, or there is no return. The following is an explanation:

1. Function

  exec ( string $command [, array &$output [, int &$return_var ]] ) : string
  参数说明:
  1.$command   要执行的命令
  2.$output  执行结果
  3.$return_var 若同时设置 $output 和此变量，命令执行后的返回状态会被写入到此变量

2. Example

  exec("ping www.baidu.com", $output);

Normally executed The result will be the same as executing ping directly on the server, but unexpected situations may occur due to certain reasons. The following are explanations of the two situations and solutions

2.1 Permission issues

Question

When we execute Linux system commands directly on the server (here, take ping as an example), the execution permission depends on the permissions of our logged-in user. If our logged-in user is root, then ping is executed using root. But when we access the website, our user at this time is www. If we do not modify the execution permission of ping, it will not be executed successfully.

Solution

Modify the execution permission of ping or the corresponding command

2.2 Command path problem

Problem

There is another situation, when When we use exec to execute a certain command, no error is reported or results are returned. The reason is that this command is not in the directory configured with environment variables, that is, in the /etc/profile file, ending with ifconfigFor example, we can use whereis ifconfig to find out the specific path of this command. For example, the path is under /usr/sbin. There are two solutions:

Solution

1 Copy the command to /usr/bin, which is the directory under the environment variable (not recommended)
2 Directly complete the full path of the command exec( '/usr/sbin',$output);(recommended)
3 Add the target directory to the environment variable, for example, add /usr/sbin to the directory

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