The Linux process terminates

Process exit in Linux is divided into normal exit and abnormal exit

1. Normal exit

(1) Execute return in the main () function

(2) Call the exit () function

(3) Call the _exit () function

2. Abnormal exit

(1) Call the About () function

(2) a process receives a signal that causes the process to terminate

Contrast

(1) Exit and return

Exit: a function with parameters. Leave control to the system after exit executes

Return: Returns after the function has finished executing. Return control to the calling function after execution

(2) Exit and about

Exit: Normal termination process

About: Abnormal termination process

(3) Exit and _exit

same : Both are used to terminate the process. When the program executes to exit or _exit, the system unconditionally stops all remaining operations, clearly includes the various data structures including the PCB, and terminates the operation of this process.

The parameter Exit_code in exit is 0 for normal termination of the process, and if other values indicate an error occurred during program execution

Similarities and differences : The header file of the exit () function-->stdlib.h

The header file of the _exit () function-->unistd.h

_exit () returns to the kernel immediately after execution, and exit () performs some cleanup work before handing over control to the kernel

When the _exit () function is called, it closes all file descriptors of the process, cleans up memory and some other kernel cleanup functions, but does not flush the stream (STDIN,STDOUT,STDERR, etc.)

The exit () function is a wrapper over the _exit () function, which invokes the _exit () function and flushes the stream before the call

eg

Exit.c

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Makefile

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Execution Result:

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_exit.c

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Makefile

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Execution results

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The printf () function is a way to use buffered I/O, which automatically reads a record from a buffer when it encounters a "\ n" line break. Therefore, exit () exits when the buffer's data is finished, and the _exit () function exits directly

If you change the _exit.c in buffer to "this was the content in buffer \ n",

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The result is

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If you change the "using _exit\n" to "Using _exit",

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The result is

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This article is from the "Voice of the Heart" blog, be sure to keep this source http://ljy789.blog.51cto.com/10697684/1828226

The Linux process terminates