UNIX Environment Advanced Programming Learning Note (iv): Process environment

1 exit function and _exit function

#include <stdlib.h>void exit (int  status)void _exit (int status)

The difference between these two functions is that the exit function performs cleanup before entering the kernel (cleanup I/O buffering), and the_exit function goes directly into the kernel

2 atexit function, register function, execute at exit

int atexit (void (* func) (void));

The functions that are registered are called termination handlers, which are called in the reverse order of registration, and are called multiple times if a function is registered multiple times.

3 malloc function and calloc function

#include <stdlib.h>void * malloc (size_t size)void* CALLOC (size_t nobj, size_t Size

malloc allocates space according to number of bytes,calloc allocates space according to number of objects

4 getenv, get environment variable

#include <stdlib.h>Char* getenv (constChar* name)

Get value by name

5 putenv,setenv,unsetenv function

int putenv (char* str)int setenv (constcharconst  charint  rewrite)int unsetenv (char* name)

Putenv takes the "Name=value" form of the string as a parameter, adds it to the environment,

Unsetenv Delete The term "name"

UNIX Environment Advanced Programming Learning Note (iv): Process environment