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PHP has several commonly used functions for executing system commands, such as: system function, exec function, popen function, passthru, shell_exec function. They can all execute system commands, but the prerequisite is that the system has given permission.
system function
Description: Execute external program and display output data.
Syntax: string system(string command, int [return_var]);
Return value: string
Detailed introduction:
This function is like the function system() in C language, which is used to execute instructions and output the results. If the return_var parameter exists, the status after executing the command will be filled in return_var. It is also worth noting that if you need to process the data entered by the user, but want to prevent the user from playing tricks to crack the system, you can use EscapeShellCmd(). If PHP is executed in a modular fashion, this function will automatically update the output buffer buffer of the web server after each line of output. If you need to return a complete string and don't want to go through unnecessary other intermediate output interfaces, you can use PassThru().
Example code:
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$last_line = system("ls", $retval); Return value: " . $retval; ?> |
exec function
Description: Execute external program.
Return value: string
Detailed introduction:
This function executes the external program or external instruction input command. Its return string is only the last line returned after the external program is executed; if you need a complete return string, you can use the PassThru() function.If the parameter array exists, the command will add the array to the parameter for execution. If you do not want the array to be processed, you can call unset() before executing exec(). If both return_var and array parameters exist, the status after executing the command will be filled in return_var.
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< ?php |
It is worth noting that if you need to process the data entered by the user and prevent the user from playing tricks to crack the system, you can use EscapeShellCmd().
Example code:
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< ?php
echo exec("whoami"); |
popen function
Description: Open the file.
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< ? |
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< ?<🎜> $fp = popen( "/bin/ls", "r" );<🎜> ?> |
Use function passthru to execute external system commands
Prototype: function passthru(string $command,int[optional] $return_value)
Knowledge point: The difference between passthru and system. passthru directly outputs the results to the browser without returning any value, and it can output binary, such as image data.
Method 4: Backtick` (in the same key as ~) executes external system commands
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echo `dir`; ?>
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