APUE第八章学习笔记

/**********************************************************包含头文件:  #include <unistd.h>函数原型:   pid_t   getpid(void);            pid_t   getppid(void);            uid_t   getuid(void);            uid_t   geteuid(void);            gid_t   getgid(void);            gid_t   getegid(void);返回值: getpid： 返回调用进程ID        getppid：返回调用进程父进程ID        getuid:   返回调用进程实际用户ID        geteuid：返回调用进程有效用户ID        getgid:  返回调用进程实际组ID        getegid: 返回调用进程有效组ID***********************************************************/

vi 8.1.c

#include <unistd.h>#include <stdio.h>#include <stdlib.h>int main(){    printf("调用进程ID: %d\n",getpid());    printf("调用进程父进程ID: %d\n",getppid());    printf("调用进程实际用户ID: %d\n",getuid());    printf("调用进程有效用户ID: %d\n",geteuid());    printf("调用进程实际组ID:  %d\n",getgid());    printf("调用进程有效组ID:   %d\n",getegid());    exit(0);}

/*****************************************************包含头文件:  #include <unistd.h>函数原型:   pid_t fork(void);函数说明: 一个现有的进程可以调用fork函数创建一个进程返回值: 子进程返回0，父进程返回进程ID，若出错,返回-1******************************************************/

#include <unistd.h>#include <stdio.h>#include <stdlib.h>int main(){    int i = 0;    int pid;    printf("before fork\n");    if ((pid = fork()) < 0)    {    printf("fork error\n");    exit(0);    }    else if (pid == 0)    {    printf("forking\n");    ++i;    }    else    sleep(2);    printf("i = %d\n",i);    exit(0);}

运行:

/*********************************************************包含头文件:  #include <sys/wait.h>函数原型:   pid_t wait(int *statloc);参数说明: statloc是一个整型指针,如果statloc不是空指针,则终止进程的状态就存放在这里,若statloc是空指针,则不关心终止状态函数说明: (1) 若所有子进程都未终止,则阻塞(2) 若有任意一个子进程终止,则该函数得到子进程终止状态,立即返回(3)若该进程无子进程,则出错返回返回值: 若成功,返回进程ID，若出错,返回0***********************************************************/

vi 8.3.c

#include <stdio.h>#include <stdlib.h>#include <sys/wait.h>#include <unistd.h>int main(){    pid_t p1;    pid_t p2;    pid_t p3;    pid_t pw;    int statloc;    if ((p1 = fork()) < 0)    {    printf("1: fork error\n");    exit(0);    }    else if (p1 == 0)    {    printf("子进程1 ID: %d\n",getpid());    sleep(8);    exit(0);    }    else    {    if ((p2 = fork()) < 0)    {        printf("2: fork error\n");        exit(0);    }    else if (p2 == 0)    {        printf("子进程2 ID: %d\n",getpid());        sleep(2);        exit(0);    }    else    {        if ((p3 = fork()) < 0)        {        printf("3: fork eror\n");        exit(0);        }        else if (p3 == 0)        {        printf("子进程3 ID: %d\n",getpid());        sleep(5);        exit(0);        }        if ((pw = wait(&statloc)) > 0)        {        printf("首先结束的进程为 %d\n",pw);        }        else        printf("wait error\n");    }    }    return 0;}

/***********************************************************包含头文件:  #include <sys/wait.h>函数原型： pid_t waitpid(pid_t pid,int *statloc,int options);函数说明:  waitpid并不等待调用之后的第一个终止子进程 ，它有若干个选项，可以控制它所等待的进程返回值:若成功,返回进程ID,若出错,返回0或-1**********************************************************/

vi 8.4.c

#include <stdio.h>#include <sys/wait.h>#include <stdlib.h>#include <unistd.h>int main(){    pid_t ps1;    pid_t ps2;    if ((ps1 = fork()) < 0)    {    printf("1:fork error\n");    exit(0);    }    else if (ps1 == 0)    {    printf("1: forking\n");    sleep(7);    exit(0);    }    if ((ps2 = fork()) < 0)    {    printf("2: forking error\n");    exit(0);     }    else if (ps2 == 0)    {    printf("2: forking\n");    sleep(4);    exit(0);    }    if (waitpid(ps1,NULL,0) != ps1)    printf("waitpid 1 error\n");    else    printf("forking 1 has exited\n");    if (waitpid(ps2,NULL,0) != ps2)    printf("waitpid 2 has error\n");    else    printf("forking 2 has exited\n");    return 0;}

vi 8.5.c

/*********************************************************包含头文件:  #include    <sys/wait.h>函数原型:   int waitid(idtype_t idtype,id_t id,siginfo_t *infop,int options);参数说明:   idtype_t:常量                          说明P_PID                       等待某一特定进程idP_PGID                  等待某进程组中的任一idP_ALL                       等待任一id options是下列的常量按位或运算:WCONTINUED(等待一进程,他以前曾被停止,此后又继续,但其状态尚未报告)WEXITED(等待已退出的进程)WNOHANG(如无可用的子进程退出状态,立即返回而非阻塞)WNOWAIT(不破坏子进程退出状态,该子进程退出状态,可由后续函数取得)WSTOPPED(等待一进程,它已经停止,但状态尚未报告)返回值: 若成功,返回0，若失败,返回-1**********************************************************/

vi 8.5.c

#include <sys/wait.h>#include <unistd.h>#include <stdio.h>#include <stdlib.h>int main(){    pid_t ps1;    pid_t ps2;    if ((ps1 = fork()) < 0)    {    printf("1 fork error\n");    exit(0);    }    else if (ps1 == 0)    {    printf("1: forking\n");    sleep(2);    exit(0);    }    if ((ps2 = fork()) < 0)    {    printf("2 fork error\n");    exit(0);    }    else if (ps2 == 0)    {    printf("2: forking\n");    sleep(8);    exit(0);    }    if (waitid(P_PID,ps1,NULL,WEXITED) == 0)    {    printf("1 fork has exited\n");    }    if (waitid(P_PID,ps2,NULL,WEXITED) == 0)    {    printf("2 fork has exited\n");    }    return 0;}

/***********************************************************包含头文件:  #include <sys/wait.h>                #include <sys/type.h>                #include <sys/time.h>                #include <sys/resource.h>函数原型:   pid_t wait3(int *statloc,int options,struct rusage* rusage);pid_t wait4(pid_t pid,int *statloc,int options,struct rusage *rusage);函数说明：   资源统计信息包括用户CPU时间总量,系统CPU时间总量,缺页次数,接受到信号的次数等，返回由终止进程及其所有子进程使用的资源概况返回值:    若成功,返回进程ID，若出错，返回-1**********************************************************/

vi 8.6.c

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/wait.h>static void charatatime(char *);int main(){    pid_t pid;    if ((pid = fork()) < 0)    {    printf("fork error\n");    exit(0);    }    else if (pid == 0)    {    charatatime("output from child\n");    }    else    {    charatatime("ouput from parent\n");    }    return 0;}static void charatatime(char *str){    char *ptr;    int c;    setbuf(stdout,NULL);    for (ptr = str; (c = *ptr++) != 0;)    putc(c,stdout);}

/**********************************************************包含头文件:  #include <unistd.h>函数原型:   int execl(const char* pathname,const char* arg0,    …/*(char*)0*/);int execv(const char* pathname,char *const argv[]);int execle(const char* pathname,const char* arg0,       …/*(char*)0,char char *const envp[] */);int execve(const char* pathname,char *const argv[],char *const envp[]);int execlp(const char* filename,const char* arg0,…/*(char*)0*/);int execvp(const char* pathname,char *const envp[]);int fexecve(int fd,char *const argv[],char *const envp[]);函数说明: 多用也就会了返回值:若出错,返回-1，若成功,不返回************************************************************/

vi echoarg.c

#include <stdio.h>#include <stdlib.h>int main(int argc,char *argv[]){    for (int i = 0; i < argc; ++i)    {    printf("argv[%d]:  %s\n",i,argv[i]);    }    return 0;}

vi 8.7.c

#include <unistd.h>#include <stdio.h>#include <stdlib.h>int main(){    pid_t pid;    if ((pid = fork()) < 0)    {    printf("fork error\n");    }    else if (pid == 0)    {    execlp("/home/marco/echoarg.out","Marco","is good","man",(char*)0);    exit(0);    }    exit(0);}

vi echoget.c

#include <stdio.h>#include <stdlib.h>int main(int argc,char* argv[]){    int i;    char **ptr;    extern char **environ;    for (int i = 0; i < argc; ++i)    printf("argv[%d]:  %s\n",i,argv[i]);    for (ptr = environ; *ptr != 0; ++ptr)    printf("environmet: %s\n",*ptr);    return 0;}

vi 8.8.c

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/wait.h>char *env_init[] = {"name = Marco","PATH = /home/marco/8.8.c",NULL};int main(){    pid_t pid;    if ((pid = fork()) < 0)    {    printf("fork error\n");    exit(0);    }    else if (pid == 0)    {    execle("/home/marco/echoget.out","Marco","is a","king",NULL,env_init);    exit(0);    }    if (waitpid(pid,NULL,0) != pid)    printf("waitpid error\n");    return 0;}

/******************************************************包含头文件:  #include <unistd.h>函数原型:   int setuid(uid_t uid);            int setgid(gid_t gid);函数说明:   设置实际用户ID和有效用户ID            设置实际用户组ID和有效组ID返回值:若成功,返回0,若失败,返回-1********************************************************/

/*******************************************************包含头文件:  #include <unistd.h>函数原型:   int setreuid(uid_t ruid,uid_t euid);            int setregid(gid_t rgid,gid_t egid);函数说明:交换实际用户ID和有效用户ID的值返回值:    若成功,返回0，若出错，返回-1******************************************************/

/**********************************************************包含头文件:  #include <unistd.h>函数原型:   int seteuid(uid_t uid);            int setegid(gid_t gid);函数说明:设置有效用户ID或有效用户组ID返回值:若成功,返回0，若出错,返回-1********************************************************/

/***********************************************************包含头文件:  #include <stdlib.h>函数原型:   int system(const char* cmdstring);函数说明:执行cmdstring程序返回值:(1):fork失败或者waitpid返回除EINTR之外的出错,则system返回-1,并且设置errno以指示错误类型(2):如果exec失败(表示不能执行shell)，则其返回值如同shell执行了exit一样(3):否则所有3个函数(fork，exec和waitpid)都成功,那么system的返回值是shell的终止状态,其格式已在waitpid中说明***********************************************************/

vi 8.9.c

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/wait.h>char *env_init[] = {"name = Marco","PATH = /home/marco/8.8.c",NULL};int main(){    pid_t pid;    if ((pid = fork()) < 0)    {    printf("fork error\n");    exit(0);    }    else if (pid == 0)    {    execle("/home/marco/echoget.out","Marco","is a","king",NULL,env_init);    exit(0);    }    if (waitpid(pid,NULL,0) != pid)    printf("waitpid error\n");    return 0;}

/********************************************************包含头文件:  #include <unistd.h>函数原型:   char *getlogin(void);函数说明:获取用户登录的名字返回值:若成功,返回指向登录名字字符串的指针,若出错,返回NULL注:如果调用此函数的进程没有连接到用户登录时所用的终端,则函数会失败,通常称这些进程为守护进程*********************************************************/

#include <stdio.h>#include <stdlib.h>#include  <unistd.h>int main(){    char *ptr;    if ((ptr = getlogin()) == NULL)    {    printf("getlogin error\n");    exit(0);    }    else    printf("运行该程序的用户登录名:  %s\n",ptr);    return 0;}

/****************************************************包含头文件：  #include <unistd.h>函数原型:   int nice(int incr);函数说明:获取或更改进程的nice值,提高或降低进程调度优先级(nice越小,优先级越高 ,nice的范围在(2 * NZERO) – 1之间,NZERO是系统默认的nice值返回值:若成功,返回新的nice值NZERO;若出错,返回-1注:-1是合法的成功返回值,如果nice调用成功,返回值为-1，则errno为0，否则,nice调用失败如果inr太小(太大),系统会自动升高(降低)到最小(最大)合法值*********************************************************//*********************************************************包含头文件:  #include <sys/resource.h>函数原型:   int getpriority(int which,id_t who);参数说明: which参数可以取以下三个值:PRIO_PROCESS    表示进程PRIO_PGRP   表示进程组PRIO_USER   表示用户ID当which设为PRIO_USER并且who为0,使用调用进程的实际用户ID当which作用于多个进程,则返回所有作用进程中优先级最高的(最小的nice值)函数说明: 获取进程或一组相关进程的nice值返回值:若成功,返回-NZERO ~ NZERO – 1之间的nice值,若出错,返回-1*******************************************************//********************************************************包含头文件:  #include <sys/resource.h>函数原型:   int setpriority(int which,id_t who,int value);函数说明:为进程,进程组和属于特定用户ID的所有进程设置优先级返回值:若成功,返回0,若失败,返回-1*******************************************************/

vi 8.10.1.c

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>int main(){    int ret;    if ((ret = nice(sysconf(_SC_NZERO) - 2)) == -1)    {    if (errno != 0)    {        printf("nice error\n");        exit(0);    }    }    else    printf("%d\n",ret);    return 0;}

vi 8.10.2.c

#include <stdio.h>#include <stdlib.h>#include <sys/resource.h>#include <errno.h>#include <sys/time.h>#include <unistd.h>unsigned long long count;struct timeval end;void checktime(char *str){    struct timeval tv;    gettimeofday(&tv,NULL);    if (tv.tv_sec >= end.tv_sec && tv.tv_usec >= end.tv_usec)    {    printf("%s  count = %lld\n",str,count);    exit(0);    }}int main(int argc,char *argv[]){    pid_t pid;    char *s;    int nzero,ret;    int adj = 0;    setbuf(stdout,NULL);    nzero = sysconf(_SC_NZERO);    printf("NZERO = %d\n",nzero);    if (argc == 2)    adj = strtol(argv[1],NULL,10);    gettimeofday(&end,NULL);    end.tv_sec += 10;    if ((pid = fork()) < 0)    {    printf("fork error\n");    exit(0);    }    else if (pid == 0)    {    s = "child";    printf("current nice value is %d,adjustfily by %d\n",nice(0) + nzero,adj);    errno = 0;    if ((ret = nice(adj)) == -1 && errno != 0)    {    printf("nice error\n");    exit(0);    }    printf("now child nice value is %d\n",ret + nzero);    }    else    {    s = "parent";    printf("current nice value in parent is %d\n",nice(0) + nzero);    }    for (;;)    {    if (++count == 0)    {        printf("%s counter wrap\n",s);        exit(0);    }    checktime(s);    }    return 0;}

vi 8.11.c

#include <stdio.h>#include <stdlib.h>#include <sys/resource.h>#include <unistd.h>#include <errno.h>int main(){    int ret;    int n;    errno = 0;   /* if ((n = nice(sysconf(_SC_NZERO))) == -1 && errno == -1)    {    printf("nice error\n");    exit(0);    }    printf("%d\n",n);*/    if (setpriority(PRIO_PROCESS,getpid(),5) < 0)    {    printf("setpriority error\n");    exit(0);    }    if ((ret = getpriority(PRIO_PROCESS,getpid())) == -1)    {    printf("getpriority error\n");    exit(0);    }    printf("%d\n",ret);    return 0;}

/*******************************************************包含头文件:  #include <sys/times.h>函数原型:   clock_t times(struct tms *buf);参数说明:   struct tms{    clock_t tms_utime;      //用户CPU时间    clock_t tms_stime;      //系统CPU时间    clock_t tms_cutime;    //用户CPU时间 (子进程终止)    clock_t tms_cstime; //系统CPU时间(子进程终止)}函数说明:获得进程时间返回值:    若成功,返回流逝的墙上时钟时间(以时钟滴答数为单位);若出错,返回-1******************************************************/

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/wait.h>#include <sys/times.h>long clktck;void print_time(clock_t pass,struct tms start,struct tms end){    printf("流逝 %7.2f 秒\n",pass /(double) clktck);    printf("用户CPU时间  %7.2f秒\n",(end.tms_utime - start.tms_utime) /(double) clktck);    printf("系统CPU时间  %7.2f秒\n",(end.tms_stime - start.tms_stime) /(double) clktck);    printf("子进程用户CPU时间   %7.2f秒\n",(end.tms_cutime - start.tms_cutime) /(double) clktck);    printf("子进程系统CPU时间   %7.2f秒\n",(end.tms_cstime - start.tms_cstime) /(double) clktck);}int main (){    if ((clktck = sysconf(_SC_CLK_TCK)) < 0)    {    printf("sysconf error\n");    exit(0);    }    struct tms start;    clock_t s;    if ((s = times(&start)) < 0)    {    printf("times error\n");    exit(0);    }    pid_t pid;    if ((pid = fork()) < 0)    {    printf("fork error\n");    exit(0);    }    else if (pid == 0)    {    sleep(6);    printf("in child\n");    clock_t child;    struct tms end;    if ((child = times(&end)) < 0)    {        printf("times error\n");        exit(0);    }    print_time(child - s,start,end);    exit(0);    }    else    {    sleep(2);    printf("in parent\n");    struct tms end;    clock_t parent;    if ((parent = times(&end)) < 0)    {        printf("times error\n");        exit(0);    }    print_time(parent - s,start,end);    }    return 0;}