一、linux下高级应用编程--stdio.h

stdio.h 标准函数输入/输出

<stdio.h>头文件中用一些整数定义下列一些宏：

BUFSIZ：<stdio.h>中缓冲区的大小

_IOFBF：输入/输出全缓冲.

_IOLBF：输入/输出行缓冲.当向缓冲区输入一个换行符时，缓冲区的内容会被flush。

_IONBF：输入/输出不缓冲.

L_ctermid

^[CX] Maximum size of character array to holdctermid() output.

L_tmpnam

Maximum size of character array to hold tmpnam() output.

SEEK_CUR

Seek relative to current position.

SEEK_END

Seek relative to end-of-file.

SEEK_SET

Seek relative to start-of-file.

The following macros shall be defined as positive integer constant expressions which denote implementation limits:

{FILENAME_MAX}

Maximum size in bytes of the longest filename string that the implementation guarantees can be opened.

{FOPEN_MAX}

Number of streams which the implementation guarantees can be open simultaneously. The value is at least eight.

{TMP_MAX}

Minimum number of unique filenames generated by tmpnam(). Maximum number of timesan application can call tmpnam() reliably. The value of {TMP_MAX} is at least 25.^[XSI] On XSI-conformant systems, the value of {TMP_MAX} is at least 10000.

The following macro name shall be defined as a negative integer constant expression:

EOF

End-of-file return value.

The following macro name shall be defined as a null pointer constant:

NULL

Null pointer.

The following macro name shall be defined as a string constant:

P_tmpdir

^[XSI] Default directory prefix fortempnam().

定义函数：int fflush(FILE *stream)

函数说明：fflush()会强迫将缓冲区内的数据写回参数stream指定的文件中。如果参数stream为NULL， fflush()会将所有打开的文件数据更新。
返回值   ：成功则返回0,  失败返回EOF, 错误代码存于errno中