相关函数

一：

    1_3:  (1) DIR *opendir(const char *name);    <dirent.h>

             (2) DIR *fdopendir(int fd);                    

                          On error, NULL is returned;

             (3) struct dirent *readdir( DIR *dp)        <dirent.h>

                          On error, NULL is returned;

             (4) int closedir(DIR *dp);                      <dirent.h>

                          0 on success, -1 on error.

 

    1_4:  (1) ssize_t read(int fd, void *buf, size_t count);        

                  On success, return the number of bytes read, maybe smaller than count, and the file position is advanced by the number.

                  On error, -1 returned.

            (2) ssize_t  write(int fd, void *buf, size_t count);

                 On success, return the number of bytes writetten, maybe bigger than count.

 

    1_5: (1) int getc(FILE *stream);   <stdio.h>

                On success, return the charactor read as an unsigned char cast to an int, or EOF end of file.

            (2) int putc(int c, FILE *stream)     <stdio.h>

                On success, return the haractor read as an unsigned char cast to an int.

                On error, return EOF.

    1_6: (1) pid_t getpid(void);      <unistd.h>

                  return the process ID of the calling process.

                 pid_t getppid(void);

                  return the process ID of the parent of the calling process.

 

    1_7: (1)  char *fgets(char *s, int size, FILE *stream);

                  fgets() reads in at most one less than size characters from stream and stores them into the buffer pointed to by s.  Reading stops after an EOF or a newline.

                  On success, return s.

                  Return NULL, on error or shen EOF occurs while no charactor have been read.