写给linux编程的初学者，进程编程是linux编程首先要学习的东西，往后要学习进程之间通讯的一些编程。下面的是进程编程的一些基本函数。1．用户标识（UID）和有效用户标识（EUID）使用getuid函数和geteuid函数来获取当前进程的用户标识和有效用户标识#include<stdio.h>#include<sys/types.h>#include<unistd.h>intmain(void){printf("CurrentprocessUID:%ld\n",(long)getuid());printf("CurrentporcessEUID:%ld\n",(long)geteuid());return0;}运行结果：CurrentprocessUID:500CurrentprocessEUID:5002.fork函数通过fork函数并判断函数返回值，根据返回值来判断是在父进程还是子进程。#include<stdio.h>#include<unistd.h>#include<sys/types.h>intmain(void){pid_tpid;//fork函数如果返回值小于0，表示调用失败//如果返回值为0，表示处于进程中，如果大于0，表示在父进程中if((pid=fork())<0){perror("Cannotcreatethenewprocess");return1;}elseif(pid==0){printf("Inthechildprocess!\n");return0;}else{printf("Intheparentprocess!\n");return0;}}运行结果：Inthechildprocesss!!Intheparentprocess!!调用fork函数后，其后代码会被父子进程分别执行。#include<stdio.h>#include<unistd.h>#include<sys/types.h>intmain(void){fork();printf("Willbeexecutedtwice\n");return0;}运行结果：WillbeexcutedtwiceWillbeexcutedtwice3.vfork函数首先定义g_var为全局变量，var为局部变量，然后调用fork函数创建子进程，并在子进程对g_var变量和var变量进行修改。子进程在输出这两个变脸值后退出，输出父进程中的这两个变量的取值情况。#include<stdio.h>#include<unistd.h>#include<sys/types.h>intg_var=0;intmain(void){pid_tpid;intvar=1;printf("processid:%ld\n",(long)getpid());printf("beforeexecutetheforksystemcall,g_var=%dvar=%d\n",g_var,var);if((pid=fork())<0){perror("Cannotcreateanewprocess");return1;}elseif(pid==0){g_var++;var++;printf("processid:%ld,g_var=%dvar=%d\n",(long)getpid(),g_var,var);_exit(0);}printf("processid:%ld,g_var=%dvar=%d\n",(long)getpid(),g_var,var);return0;}运行结果：Processid:24437Beforeexcutetheforksystemcall,g_var=0var=1Processid:24438,g_var=1var=2Processid:24437,g_var=0var=1修改上面的程序，将fork函数的语句进行替换，使用vfork函数，将代码保存并运行#include<stdio.h>#include<unistd.h>#include<sys/types.h>intg_var=0;intmain(void){pid_tpid;intvar=1;printf("processid:%ld\n",(long)getpid());printf("beforeexecutetheforksystemcall,g_var=%dvar=%d\n",g_var,var);if((pid=vfork())<0){perror("Cannotcreateanewprocess")