注意点：exec族函数的使用
以execl为例：
（1）
（2）exec族函数中的函数调用失败时会设置error并返回-1，然后从源程序调用点接着往下执行。
执行成功后不会返回，也不会从源程序调用点接着往下执行。
exec族函数一般配合fork使用；
创建子进程后，在子进程中调用exec组函数处理事情；
exec族函数允许成功后不会返回，也不会继续执行，而是结束子进程，且子进程的结束状态为0（相当于调用exit(0)结束子进程）
二，验证“exec族函数允许成功后不会返回，也不会继续执行，而是结束子进程，且子进程的结束状态为0（相当于调用exit(0)结束子进程）”
父进程在等待子进程结束，如果子进程结束了，会打印结束状态；
函数中未使用exit(0);
status_childProcess初值被设置为-1了；
子进程结束状态为0；
证明execl运行成功后主动结束了子进程；
程序的完整代码：
mainc
#include "./io.h"
struct CMD_input CMD_test1={"creat","copy","display","delete","write"};
struct buffer_param *p;
int main(int argc,char **argv)
{
//printf("argc :%d,argv[0]:%s,argv[1]:%s,argv[2]:%s\r\n",argc,argv[0],argv[1],argv[2]);
//agrc指在终端输入的个数
//argv[0]是第1个参数；
//argv[1]是第二个参数；，，，，，，
//1-function:解析参数1。判断要做什么操作
//当前只接解析“creat”,但是预留“cp”,"display","delete"接口
p = ( struct buffer_param *)malloc(sizeof(struct buffer_param));
memset(p,0,sizeof(struct buffer_param));
strncpy(p->buffer_param0,argv[0],strlen(argv[0]));
strncpy(p->buffer_param1,argv[1],strlen(argv[1]));
strncpy(p->buffer_param2,argv[2],strlen(argv[2]));
if(argc==4)
{
strncpy(p->buffer_param3,argv[3],strlen(argv[3]));
}
log_test1();//打印所有参数
read_CMD();//读取指令“creat,write,delete,display,copy”
task_sch();//执行任务
return 0;
}
io.c文章来源：https://www.toymoban.com/news/detail-463713.html
#include "./io.h"
extern struct buffer_param *p;
extern struct CMD_input CMD_test1;
int flag_of_QUITEDIT=0;
char path_of_file[30];
char flag_of_key_event=0;
void log_test1()
{
printf("param0:%s\r\n",p->buffer_param0);
printf("param1:%s\r\n",p->buffer_param1);
printf("param2:%s\r\n",p->buffer_param2);
printf("param3:%s\r\n",p->buffer_param3);
}
int read_CMD()
{
if(strncmp(p->buffer_param1,CMD_test1.CMD_CREAT,strlen(p->buffer_param1))==0)//creat
{
memset(path_of_file,0,sizeof(path_of_file));
sprintf(path_of_file,"./%s",p->buffer_param2);
flag_of_key_event = Key_event_creatFile;
//creat(buffer_param2, S_IRWXU);
}
else if(strncmp(p->buffer_param1,CMD_test1.CMD_WRITE,strlen(p->buffer_param1))==0)//write
{
memset(path_of_file,0,sizeof(path_of_file));
sprintf(path_of_file,"./%s",p->buffer_param2);
flag_of_key_event = Key_event_writeFile;///写入数据
}
else if(strncmp(p->buffer_param1,CMD_test1.CMD_DISPLAY,strlen(p->buffer_param1))==0)//display
{
memset(path_of_file,0,sizeof(path_of_file));
sprintf(path_of_file,"cat ./%s",p->buffer_param2);
flag_of_key_event = Key_event_displayFile;///
}
else if(strncmp(p->buffer_param1,CMD_test1.CMD_CP,strlen(p->buffer_param1))==0)//copy
{
memset(path_of_file,0,sizeof(path_of_file));
sprintf(path_of_file,"cp ./%s ./%s",p->buffer_param2,p->buffer_param3);
flag_of_key_event = Key_event_copyFile;///
}
else if(strncmp(p->buffer_param1,CMD_test1.CMD_DELETA,strlen(p->buffer_param1))==0)//display
{
memset(path_of_file,0,sizeof(path_of_file));
sprintf(path_of_file,"rm ./%s",p->buffer_param2);
flag_of_key_event = Key_event_deleteFile;///
}
return 0;
}
int task_sch()
{
int return_of_fork;
int status_childProcess;//子进程退出状态
switch(flag_of_key_event)
{
case Key_event_creatFile:
return_of_fork = fork();//创建1个子进程
if(return_of_fork<0)
printf("creat childprocess failed\r\n");
else if(return_of_fork==0)
creat_file();
else if(return_of_fork>0)
wait(NULL);
break;
case Key_event_writeFile:
return_of_fork = fork();//创建1个子进程
if(return_of_fork<0)
printf("creat childprocess failed\r\n");
else if(return_of_fork==0)
write_file();
else if(return_of_fork>0)
wait(&status_childProcess);
printf("child process exit status:%d\n",WEXITSTATUS(status_childProcess));
break;
case Key_event_displayFile:
return_of_fork = fork();//创建1个子进程
if(return_of_fork<0)
printf("creat childprocess failed\r\n");
else if(return_of_fork==0)
display_file();
else if(return_of_fork>0)
wait(&status_childProcess);
printf("child process exit status:%d\n",WEXITSTATUS(status_childProcess));
break;
case Key_event_copyFile:
return_of_fork = fork();//创建1个子进程
if(return_of_fork<0)
printf("creat childprocess failed\r\n");
else if(return_of_fork==0)
copy_file();
else if(return_of_fork>0)
wait(&status_childProcess);
printf("child process exit status:%d\n",WEXITSTATUS(status_childProcess));
break;
case Key_event_deleteFile:
return_of_fork = fork();//创建1个子进程
if(return_of_fork<0)
printf("creat childprocess failed\r\n");
else if(return_of_fork==0)
delete_file();
else if(return_of_fork>0)
wait(&status_childProcess);
printf("child process exit status:%d\n",WEXITSTATUS(status_childProcess));
break;
default :break;
}
}
int creat_file()
{
int ret=0;
ret = creat(p->buffer_param2, S_IRWXU);//
if(ret==-1)
{
printf("creat file failed\r\n");
}
exit(Key_event_creatFile);//退出子进程
return ret;
}
int write_file()
{
int ret=0;
int fd=0;
char readbuffer[128]={0};
fd = open(path_of_file,O_RDWR | O_CREAT,0666) ;
if(fd == -1)
{
printf("unexist %s\n",path_of_file);
}
else
{
printf("open file1 success\n");
printf("if you want exit edit ,please input “QUIT”\r\n");
printf("please input string :\r\n");
while(flag_of_QUITEDIT==0)
{
printf(">");
memset(readbuffer,0,sizeof(readbuffer));
fgets(&readbuffer[0],50,stdin);
if(strncmp(readbuffer,"QUIT",strlen("QUIT"))==0)
{
flag_of_QUITEDIT=1;
}
//add"enter"to string
{
int len;
len = strlen(readbuffer);
readbuffer[len] = '\n';
readbuffer[len+1] = '\0';
}
ret = write(fd,readbuffer,strlen(readbuffer));
if(ret == -1)
{
perror("write");
exit(-1);
}
if(flag_of_QUITEDIT==1)
{
close(fd);
exit(Key_event_writeFile);
}
}
}
}
int display_file()
{
int fd=0;
//fd = system(path_of_file);
//printf("fd = %d\r\n",fd);
fd = execl_for_cat();
if(fd>0)
{
printf("cat file failed\r\n");
}
close(fd);
//exit(Key_event_displayFile);
}
int copy_file()
{
int fd=0;
int fdSRC=0;
int fdDES=0;
char *readBuf = NULL;
//fd = system(path_of_file);
//printf("fd = %d\r\n",fd);
//使用lseek实现copy;源文件：p->buffer_param2；目标文件：p->buffer_param3
fdSRC = open(p->buffer_param2,O_RDWR);//打开文件
if(fdSRC==-1)
{
printf("src open failed\r\n");
}
else{
//源文件打开成功
int size = lseek(fdSRC,0,SEEK_END);//读取文件大小
lseek(fdSRC,0,SEEK_SET);//把光标移动到文件头部
readBuf = (char *)malloc(sizeof(char)*size + 8);//指针指向这么大的空间
int n_read = read(fdSRC, readBuf, 1024);//把源文件的数据读取到buffer中
fdDES = open(p->buffer_param3,O_RDWR|O_CREAT,0600);//创建目标文件
int n_write = write( fdDES,readBuf,strlen(readBuf));//向目标文件写入信息
close(fdSRC);
close(fdDES);
exit(Key_event_copyFile);
}
}
int delete_file()
{
int fd=0;
fd = system(path_of_file);
//printf("fd = %d\r\n",fd);
if(fd!=0)
{
printf("delete file failed\r\n");
}
exit(Key_event_deleteFile);
}
int execl_for_cat()
{
memset(path_of_file,0,sizeof(path_of_file));
sprintf(path_of_file,"./%s",p->buffer_param2);
printf("will display file by execl \r\n");
if(execl("/bin/cat","cat",path_of_file,NULL) == -1)//exec族函数中的函数调用失败时会设置error并返回-1，然后从源程序调用点接着往下执行。执行成功后不会返回，也不会从源程序调用点接着往下执行。
{
printf("exec failed\n");
}
//return 0;
}io.h文章来源地址https://www.toymoban.com/news/detail-463713.html
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/wait.h>
#define Key_event_creatFile 0x01
#define Key_event_writeFile 0x02
#define Key_event_displayFile 0x03
#define Key_event_copyFile 0x04
#define Key_event_deleteFile 0x05
struct CMD_input{
char CMD_CREAT[10];
char CMD_CP[10];
char CMD_DISPLAY[10];
char CMD_DELETA[10];
char CMD_WRITE[10];
};
struct buffer_param{
char buffer_param0[10];
char buffer_param1[10];
char buffer_param2[10];
char buffer_param3[10];
};
void log_test1();
int read_CMD();
int task_sch();
int creat_file();
int write_file();
int display_file();
int copy_file();
int delete_file();
int execl_for_cat();到了这里，关于V3.0_用exec族函数替代system()的文章就介绍完了。如果您还想了解更多内容，请在右上角搜索TOY模板网以前的文章或继续浏览下面的相关文章，希望大家以后多多支持TOY模板网！
