apue第一章:UNIX系统概览-笔记-函数

opendir, fdopendidr ---打开目录

#include <sys/types.h>
#include <dirent.h>

DIR *opendir(const char *name);
DIR *fdopendir(int fd);
struct dirent *readdir(DIR *dirp);

struct __dirstream   
   {   
    void *__fd;    
    char *__data;    
    int __entry_data;    
    char *__ptr;    
    int __entry_ptr;    
    size_t __allocation;    
    size_t __size;    
    __libc_lock_define (, __lock)    
   };   

typedef struct __dirstream DIR;  

struct dirent {
     ino_t          d_ino;       /* inode number */
     off_t          d_off;       /* not an offset; see NOTES */
     unsigned short d_reclen;    /* length of this record */
     unsigned char  d_type;      /* type of file; not supported by all filesystem types */
     char           d_name[256]; /* filename */
};

---

read write

#include <unistd.h>
/*从文件描述符fd中读取count字节到buf中*/
ssize_t read(int fd, void *buf, size_t count);
ssize_t write(int fd, const void *buf, size_t count);

---

#include <sys/types.h>
#include <unistd.h>

/*返回进程ID*/
pid_t getpid(void);
/*返回进程的父亲进程ID*/
pid_t getppid(void);

---

fork execlp

#include <sys/types.h>
#include <unistd.h>

pid_t fork(void);

---

#include <string.h>
/*返回指向错误信息字符串的指针*/
char *strerror(int errnum);

#include <stdio.h>
/*根据errno的值返回错误信息*/
void perror(const char *msg);

---

getuid getgid

#include <unistd.h>
uid_t getuid(void);
gid_t getgid(void);

---

waitpid

#include <sys/wait.h>
pid_t waitpid(pid_t pid, int *stat_loc, int options);