Run linux commands in php

Source: Internet
Author: User
Several functions used by php to execute linux commands: system function description: execute an external program and display the output information. Syntax: stringsystem (stringcommand, int [return_var]); return value: string details: This function is like the system () function in C, used to execute commands and output results. If the return_var parameter exists, execute command php to execute several functions of linux commands:

System functions
Note: execute an external program and display the output information.
Syntax: string system (string command, int [return_var]);
Return value: string

Details:
This function is like the system () function in C, used to execute commands and output results. If the return_var parameter exists, the status after command execution is filled in return_var. It is also worth noting that EscapeShellCmd () can be used to process user input data and prevent users from cracking the system by means of tricks (). If PHP is executed in a modular manner, this function automatically updates the output buffer area of the Web server after each row is output. PassThru () can be used to return complete strings without passing through any other intermediate output interface ().

Instance code:

<? Php
$ Last_line = system ('Ls', $ retval );
Echo 'last line of the output: '. $ last_line;
Echo' Return value: '. $ retval;
?>

 

Exec function
Note: execute external programs.
Syntax: string exec (string command, string [array], int [return_var]);
Return value: string

Details:
This function executes the external program or external command that inputs the command. The returned string is the last line returned after the execution of the external program. to return the complete string, you can use the PassThru () function.

If the parameter array exists, the command adds 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 the return_var and array parameters exist, the status after the command is executed is filled in return_var.

It is worth noting that EscapeShellCmd () can be used to process user input data and prevent users from cracking the system by means of tricks ().

Instance code:

<? Php
Echo exec ('whoam ');
?>

Popen function
Note: open the file.
Syntax: int popen (string command, string mode );
Return value: integer

Details:
This function executes the command to open a file, which is a file processed in pipelines. Files opened using this function can only be one-way (read-only or write-only), and must be closed using pclose. You can use fgets (), fgetss (), and fputs () in file operations (). If an error occurs when the file is opened, the value false is returned.

Instance code:

<? Php
$ Fp = popen ("/bin/ls", "r ");
?>

However, the command to be executed involves permissions. for example, run the "service network restart" command in php to restart the network. Apache is executed by a common user. My computer uses apache users and has no permission to execute this command.
Solution:
1. bypass this restriction:
First, write a c program, such as/usr/local/a. c.
# Include
Main ()
{
Uid_t uid, euid;

Uid = getuid ();
Euid = geteuid ();

If (setreuid (euid, uid ))
Perror ("setreuid ");

System ("service network restart ");
}
Compile the file,

Gcc a. c-o

At this time, the program a will be generated in the current directory
Chmod u + s./a, the owner of the program.
The uid of apache is 48. After setreuid is called, the valid user ID and the actual user ID are exchanged. (The chmod u + s must take effect) make apache's current uid 0 so that the root command can be executed.

Php program call:
Function RestartNetwork (){
System ("/usr/local/");
}
RestartNetwork ();
?> 2. edit the/etc/sudoers file or use the mongodo command.
Host_Alias SERVER = localhost, your host name
User_Alias USERLIST = apache username
Cmnd_Alias COMMANDLIST =/sbin/service # Add commands that you want apache users to use

# Defaults requiretty
......
After modification, save/etc/sudoers with only 0440 permissions.
Then, php can use the service command
System ("sudo service network restart ");
?>
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