环境变量操作函数笔记

#include <stdlib.h>#include <unistd.h>#include <stdio.h>extern char **environ;int main(void){    if(putenv("caohanghang=101")==-1){perror("putenv");}else{perror("putenv");}//////////////////////////////////////////////if(setenv("caohanghang","10",0)==-1){perror("setenv");}else{perror("setenv");}///////////////////////////////////////int i=0;char *ptr = environ[i];while(ptr!= NULL){printf("%s\n",ptr);ptr = environ[++i];}printf("================================\n");char *env=getenv("caohanghang");if(env==NULL){printf("shabi not find\n");}else{printf("%s\n",env);}/////////////////////////////////////////if(unsetenv("caohanghang")==-1){perror("unsetenv");}env=getenv("caohanghang");if(env==NULL){printf("not find\n");}else{printf("%s\n",env);}return 0;}