#include <unistd.h> 的作用
由字面意思,unistd.h是unix std的意思,是POSIX标准定义的unix类系统定义符号常量的头文件,
包含了许多UNIX系统服务的函数原型,例如read函数、write函数和getpid函数。
unistd.h在unix中类似于window中的windows.h!
#ifdef WIN32
#include <windows.h>
#else
#include <unistd.h>
#endif
unistd.h含有的常量与函数:
ssize_t read(int, void *, size_t); // 读取文件使用
int unlink(const char *);
ssize_t write(int, const void *, size_t); // 写文件
int usleep(useconds_t); // 进程休眠,单位为微妙
unsigned sleep(unsigned); // 进程休眠,单位为秒
int access(const char *, int); // 获取文件的权限
unsigned alarm(unsigned);
int chdir(const char *);
int chown(const char *, uid_t, gid_t);
int close(int); // 关闭文件
size_t confstr(int, char *, size_t);
void _exit(int);
pid_t fork(void);
#include <sys/types.h>的作用
include <sys/types.h>
基本系统数据类型
是Unix/Linux系统的基本系统数据类型的头文件,含有size_t,time_t,pid_t等类型。
NAME
sys/types.h - data types
SYNOPSIS
#include <sys/types.h>
DESCRIPTION
The <sys/types.h> header shall include definitions for at least the following types:
blkcnt_t
Used for file block counts.
blksize_t
Used for block sizes.
clock_t
Used for system times in clock ticks or CLOCKS_PER_SEC; see <time.h> .
clockid_t
Used for clock ID type in the clock and timer functions.
dev_t Used for device IDs.
fsblkcnt_t
Used for file system block counts.
fsfilcnt_t
Used for file system file counts.
gid_t Used for group IDs.
id_t Used as a general identifier; can be used to contain at least a pid_t, uid_t, or gid_t.
ino_t Used for file serial numbers.
key_t Used for XSI interprocess communication.
mode_t Used for some file attributes.
nlink_t
Used for link counts.
off_t Used for file sizes.
pid_t Used for process IDs and process group IDs.
size_t Used for sizes of objects.
ssize_t
Used for a count of bytes or an error indication.
suseconds_t
Used for time in microseconds.