[英]Is there a more efficient way to do this?
首先,是的,这是我课堂上的一项实验室活动,但是我已经提交并捍卫了这项练习。 我想知道的是,是否还有另一种方式,一种更有效的方式来编写此代码。
我们的任务是编写一个代码,该代码创建一个流程,该流程创建一个孩子,该孩子又创建另一个孩子,最后创建另一个孩子。
*编辑:为了更好的可读性,我对要求进行了编号:)
最后一个子项将显示系统中正在运行的当前进程。
然后,其父项会要求一个单词,然后使用用户的输入来创建文件。
然后,其父项会要求一个单词或短语,然后在您计算机的库中找到它(假设我输入了hi,它应该找到并列出包含hi及其目录的文件。单词hi的位置应该无关紧要)
最后,主要的父代只需打印其父代ID。
这是我完整的代码:
int main(void){
char fileName[30];
char phrase[30];
int pid = fork();
int fd[2];
pipe(fd);
if(pid==0){
printf ("CHILD1: I am the 1st child\n");
printf ("CHILD1: ID is %d \n", getpid());
printf ("CHILD1: Parent ID is %d \n", getppid());
int pid2 = fork();
if(pid2==0){
printf ("\t CHILD2: I am the 2nd child\n");
printf ("\t CHILD2: ID is %d \n", getpid());
printf ("\t CHILD2: Parent ID is %d \n", getppid());
int pid3 = fork();
if(pid3==0){
printf ("\t\t CHILD3: I am the 3rd child\n");
printf ("\t\t CHILD3: ID is %d \n", getpid());
printf ("\t\t CHILD3: Parent ID is %d \n", getppid());
execlp ("/usr/bin/top", "top", NULL);
}else if(pid3==-1){
printf ("ID is %d", getpid());
printf ("error");
exit(1);
}else{
wait(NULL);
printf ("\t CHILD2: Enter a filename: ");
scanf ("%s", fileName);
printf ("\t CHILD2: %s was succcessfully created!\n", fileName);
execlp ("/bin/touch", "touch", fileName, NULL);
}
}else if(pid2==-1){
printf ("ID is %d", getpid());
printf ("error");
exit(1);
}else{
wait(NULL);
int pid4 = fork();
if(pid4 > 0) {
printf ("CHILD1: Enter a pharse: ");
scanf ("%s", phrase);
close(fd[1]);
close(STDIN_FILENO);
dup2(fd[0],STDIN_FILENO);
execlp ("/bin/grep", "grep", phrase, NULL);
}else if (pid4 == 0) {
close(fd[0]);
close(STDOUT_FILENO);
dup2(fd[1],STDOUT_FILENO);
execlp ("/usr/bin/find", "find", NULL);
}else {
printf ("error");
}
}
}else if(pid==-1){
printf ("ID is %d", getpid());
printf ("error");
exit(1);
}else{
wait(NULL);
printf ("PARENT: I am the parent\n");
printf ("PARENT: ID is %d \n", getpid());
}
}
就运行时和行数而言,您的代码似乎相当有效,但是深层嵌套的单个主要功能对尝试阅读和理解您所做的工作的人没有多大帮助。
考虑另一种习惯用法:一种更加模块化的习惯,即流程的祖先(IMHO)更容易被审阅者遵循。 (我也调用ps而不是top,因此在该步骤中不需要键盘交互。)
我的方法更“有效”吗? 可以说是没有,尽管我更喜欢这种基于功能的子方法的直接编码。 父子进程的链接是人为的,但是您的分配当然也是如此。
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
/*
* run the passed function in a child process, and return
* from this function only if the child process runs and
* exits with status of 0.
*/
static void
run_func_in_child(void (*f)())
{
int status;
pid_t pid = fork();
switch (pid) {
case -1:
perror("fork");
exit(1);
case 0: /* child */
(*f)();
break;
default: /* parent */
if (waitpid(pid, &status, 0) == -1) {
perror("waitpid");
exit(1);
}
if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
return;
}
fprintf(stderr, "child did not exit cleanly\n");
exit(1);
}
}
/*
* scanf would be simpler, but let's protect against buffer overruns
*/
static void
get_rsp(const char *prompt, char *buf, size_t blen)
{
int bl;
printf("%s: ", prompt);
fflush(stdout);
if (fgets(buf, blen, stdin) == NULL) {
if (ferror(stdin)) {
perror("read");
}
exit(1);
}
bl = strlen(buf);
if (bl > 0 && buf[bl - 1] == '\n') {
buf[bl - 1] = '\0';
}
}
static void
child_4()
{
execlp("/usr/bin/ps", "ps", "-www", "-e", "f", NULL);
perror("exec /usr/bin/ps");
exit(1);
}
static void
child_3()
{
char buf[256];
int fd;
run_func_in_child(child_4);
get_rsp("File name", buf, sizeof buf);
if (access(buf, F_OK) == 0) {
fprintf(stderr, "%s already exists\n", buf);
exit(1);
}
if ((fd = creat(buf, 0644)) == -1) {
perror("creat");
exit(1);
}
close(fd);
printf("Created empty file %s\n", buf);
exit(0);
}
static void
child_2()
{
char buf[80];
int fd[2];
pid_t pid;
run_func_in_child(child_3);
get_rsp("Phrase", buf, sizeof buf);
if (pipe(fd) == -1) {
perror("pipe");
exit(1);
}
pid = fork();
switch (pid) {
case -1:
perror("fork");
exit(1);
case 0:
/* no explicit wait for this child-of-child
* process, but when its parent (the grep) exits,
* init becomes the parent, and does the wait
*/
dup2(fd[1], 1);
close(fd[0]);
close(fd[1]);
execlp("/usr/bin/find", "find", NULL);
perror("exec of find");
exit(1);
default:
dup2(fd[0], 0);
close(fd[0]);
close(fd[1]);
execlp("/usr/bin/grep", "grep", buf, NULL);
perror("exec of grep");
exit(1);
}
}
static void
child_1()
{
run_func_in_child(child_2);
printf("Child 1: pid is %d; ppid is %d\n", getpid(), getppid());
exit(0);
}
int
main(int ac, char *av[])
{
run_func_in_child(child_1);
return 0;
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.