编译执行
代码语言：javascript复制emacs@ubuntu:~/c$ alias gtc
alias gtc='gcc -Wall -g -o'
emacs@ubuntu:~/c$ gtc fifoB.x fifoB.c
emacs@ubuntu:~/c$ gtc fifoA.x fifoA.c
emacs@ubuntu:~/c$ 先执行fifoB.x，因为等待输入，所以会在终端挂起
代码语言：javascript复制emacs@ubuntu:~/c$ ./fifoB.x 执行fifoA.x，会立即返回
代码语言：javascript复制emacs@ubuntu:~/c$ ./fifoA.x 12345
432
emacs@ubuntu:~/c$ 这时fifoB.x 也有返回了
代码语言：javascript复制emacs@ubuntu:~/c$ ./fifoB.x
12345
54321
emacs@ubuntu:~/c$编译执行过程中没有报错，从结果来看，符合预期
access
access 函数的相关声明在 unistd.h 中
/* Values for the second argument to access.
These may be OR'd together. */
#define R_OK 4 /* Test for read permission. */
#define W_OK 2 /* Test for write permission. */
#define X_OK 1 /* Test for execute permission. */
#define F_OK 0 /* Test for existence. */
/* Test for access to NAME using the real UID and real GID. */
extern int access (__const char *__name, int __type) __THROW __nonnull ((1));使用 F_OK 来检查是否存在
errno
这个变量在 errno.h 里
#ifndef errno
extern int errno;
#endif其值的宏在 asm-generic/errno-base.h 这个文件中
emacs@ubuntu:/usr/include$ cat asm-generic/errno-base.h
#ifndef _ASM_GENERIC_ERRNO_BASE_H
#define _ASM_GENERIC_ERRNO_BASE_H
#define EPERM 1 /* Operation not permitted */
#define ENOENT 2 /* No such file or directory */
#define ESRCH 3 /* No such process */
#define EINTR 4 /* Interrupted system call */
#define EIO 5 /* I/O error */
#define ENXIO 6 /* No such device or address */
#define E2BIG 7 /* Argument list too long */
#define ENOEXEC 8 /* Exec format error */
#define EBADF 9 /* Bad file number */
#define ECHILD 10 /* No child processes */
#define EAGAIN 11 /* Try again */
#define ENOMEM 12 /* Out of memory */
#define EACCES 13 /* Permission denied */
#define EFAULT 14 /* Bad address */
#define ENOTBLK 15 /* Block device required */
#define EBUSY 16 /* Device or resource busy */
#define EEXIST 17 /* File exists */
#define EXDEV 18 /* Cross-device link */
#define ENODEV 19 /* No such device */
#define ENOTDIR 20 /* Not a directory */
#define EISDIR 21 /* Is a directory */
#define EINVAL 22 /* Invalid argument */
#define ENFILE 23 /* File table overflow */
#define EMFILE 24 /* Too many open files */
#define ENOTTY 25 /* Not a typewriter */
#define ETXTBSY 26 /* Text file busy */
#define EFBIG 27 /* File too large */
#define ENOSPC 28 /* No space left on device */
#define ESPIPE 29 /* Illegal seek */
#define EROFS 30 /* Read-only file system */
#define EMLINK 31 /* Too many links */
#define EPIPE 32 /* Broken pipe */
#define EDOM 33 /* Math argument out of domain of func */
#define ERANGE 34 /* Math result not representable */
#endif
emacs@ubuntu:/usr/include$从 #define EEXIST 17 /* File exists */ 可以获知这个宏定义代表文件已经存在
总结
以下函数可以进行有名管道的创建
- mkfifo
通过各方面资料弄懂其参数的意义和返回值的类型，是熟练掌握的基础
原文地址
