Program substitution function

Process replacement

If we want the child process to execute a “ New program ” Well ？ You have to use process replacement technology . The process remains the same , Just replace the current code and data , It's called process replacement , Process substitution does not create a new process , Sub process id It hasn't changed . Just replaced the code and data .

execl（）

path： The path of the target program to be executed
arg： Fill in the command and its parameters / Executable name
…： Variable parameter list , General filling NULL

Code example ：

The function of this program replacement is ： perform ls -a -l -n -i command .
Be careful ：execl（） You can not only use system commands , You can also use your own program , That is, fill in the path of the executable program written by yourself .

execv（）

The use of this substitution function is similar to execl（） almost , Only the incoming command is represented by an array

Code example ：

execlp（）

This function does not need to take a path , But you need the file name of the executable you want to execute , Then take the order + Parameters

Code example ：

execvp（）

This replacement function is the same as execlp be similar , Only the command and its parameters are represented by an array .

Code example ：

execle（）

The first three parameters are related to cxcl identical , The fourth parameter is passed to arg Corresponding executable program .

Code example ：
myexe.c Source file ： The function of this program is to print system environment variables

Run this code ： Print the environment variables of the system

myload.c Source file ： This code uses execle（）. use myexe This program replaces this code , take env Data is passed to this program .

function myload.c： We found that myexe No longer print system variables , Instead, we print it and send it to myexe The variable of

execve（）

This replacement function is the same as excle be similar , Only the executable program name is represented by an array .

Code example ：

Writing memory

I can't tell how to use these substitution functions , We can remember how to use these functions according to their names .
The function name has “l” , Means to write the command and its parameters
Yes “v”： Use an array to represent a command and its arguments
Yes “p”： It means no specific path is required
Yes "e": Indicates that you need to pass in your own environment variables