php exec cannot be executed

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##Permission problem:

When we execute Linux system commands directly on the server (taking ping as an example here), the execution permissions depend on the permissions of our logged-in user. If our logged-in user is root, when executing ping Use root to execute. 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.

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Solution:

Modify the execution permissions of ping or corresponding commands.

Command path problem:

When we use exec to execute a command, no error is reported and no result is returned. The reason is that this command It is not in the directory where the environment variable is configured, that is, in the /etc/profile file. Taking ifconfig as an example, we can use whereis ifconfig to find out the specific path of this command.

Solution:

1. Copy the command to /usr/bin, which is the directory under the environment variable

2. Directly enter the command Full path completion exec('/usr/sbin',$output)

3. Add the target directory to the environment variable, for example, add /usr/sbin to the directory

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