`fcntl`是C和C++中的一个系统调用,用于文件描述符的特定操作。它提供了一种执行文件锁定、获取和设置文件创建标志等功能的方法。以下是`fcntl`在C++中的一些适用场景:1. **文件锁定...
如:当count值...kernel/semaphore.c文件里: 这里我们可以看到,当获取信号量成功时,返回0,而获取信号量失败时,返回一个非0的值。在使用down_interruptible()函数获取信号量时,对返回值 信号量 。 如果在多进程中使用无名信号量 很简单创建一个信号量,然后fork()一下,当然只要在血缘的进程都可以使用,也暴露了...
printf("my pid:%d\n", getpid());intfd;intret;structflocklock;charr_buf[20];charw_buf[] ="test lock\n";charw_buf2[] ="test write lock";//打开文件fd = open("example", O_RDWR|O_APPEND|O_CREAT,700);if(-1==fd) { printf("open file error:%s\n", strerror(errno)); } writ...
importmsvcrtimportosdeflock_file(file):msvcrt.locking(file.fileno(),msvcrt.LK_RLCK,os.path.getsize(file.name))defunlock_file(file):msvcrt.locking(file.fileno(),msvcrt.LK_UNLCK,os.path.getsize(file.name))withopen('example.txt','r+')asf:lock_file(f)print("File is locked for reading an...
#include <fcntl.h> #include <unistd.h> #include <stdio.h> int main() { int fd = open("example.txt", O_WRONLY | O_CREAT, 0644); if (fd == -1) { perror("open"); return 1; } int flags = fcntl(fd, F_GETFL, 0); if (flags == -1) { perror("fcntl F_GETFL"); close...
("example_3.c",O_CREAT|O_TRUNC|O_RDWR,S_IRWXU))==-1) { my_err("open",__LINE__); } //设置文件打开方式 if((ret=fcntl(fd,F_SETFL,O_APPEND))<0) { my_err("fcntl",__LINE__); } //获取文件打开方式 if((ret=fcntl(fd,F_GETFL,0))<0) { my_err("fcntl",__LINE__); ...
#include <fcntl.h> #include <unistd.h> #include <stdio.h> int main() { int fd = open("example.txt", O_WRONLY | O_CREAT, 0644); if (fd == -1) { perror("open"); return 1; } int flags = fcntl(fd, F_GETFL, 0); if (flags == -1) { perror("fcntl F_GETFL"); close...
c int main() { const char *filename = "contacts.dat"; int fd = open_contacts_file(filename); // 添加联系人 Contact new_contact = {"Alice", "1234567890", "alice@example.com"}; write_contact(fd, &new_contact); // 读取联系人 Contact contacts[100]; ssize_t bytes_read = read...
I am new to Android Programming. I want to understand how Activity Stack is maintained for a particular Android Application and how does it changes based on user navigation. For example, if there are ... rake db:migrate error for generating model ...
The interceding update problem may be illustrated as in the following example: Process A reads a customer record from a file containing account information, including the customer's account balance and phone number. Process B now reads the same record from the same file so it has its own copy...