NAME
stdio - 标准输入输出库函数
SYNOPSIS 总览
#include <stdio.h>
FILE *stdin;
FILE *stdout;
FILE *stderr;
DESCRIPTION 描述
标注 I/O 库函数提供了一个简单而有效的，带缓冲的流输出输出接口。输入和输出被映射为逻辑的数据流，物理的 I/O 特性则被隐藏起来。库中包含的函数与宏列在下面；更多信息可以从独立的 man 手册页中得到。
将一个流关联到一个外部文件 (可能是一个物理设备) 的方法是打开 ( opening ) 这个文件，其中可能牵涉到创建一个新文件。创建已有的文件使得文件中已有的内容被丢弃。如果文件支持定位请求 (例如磁盘文件；但终端不是这样)，那么一个与文件关联的定位标记 ( file position indicator ) 被定位到文件的起始 (0 字节)，除非以追加模式打开文件。使用追加模式时，究竟定位标记位于文件的开始还是结束是没有指定的。定位标记由后续的读、写和定位请求来维护。从流中输入时，就如同字符是连续地成功调用了函数 fgetc(3) 而读入的；产生输出时，就如同所有字符是连续地成功调用了函数 fputc(3) 而输出的。
将一个流与一个与之关联的文件断开的办法是关闭 ( closing ) 这个文件。在流与文件断开之前，输出流被刷新 (任何未写入的缓冲的内容都被传输给主机环境)。在文件被关闭之后，指向 FILE 对象的指针的值是不确定的 (无用数据)。
一个文件可以继续被相同的或是不同的程序实体再次打开，它的内容可以被恢复或者修改 (如果它可以被重定位到文件开始的话)。如果 main 函数返回到它最初的调用者，或者调用了函数 exit(3) ，在程序终止前，所有打开的文件都将被关闭 (因此所有的输出流都被刷新)。其他终止程序的方法，例如 abort(3) 不会进行正常的关闭文件操作。
在程序启动时，会预先定义三个文本流，它们不需要显式地打开 --- 标准输入 (用于读入常规内容)，--- 标准输出 (用于输出常规内容)，以及 标准错误 (用于输出诊断信息)。这些流的缩写是 stdin，stdout 和 stderr 。在打开时，标准错误流不会完全缓冲；当且仅当流不是一个交互的设备时，标准输入和标准输出流才被完全缓冲。
指向终端设备的输出流总是默认使用行缓冲；未定的输出总是在指向一个终端设备的输入流被读取时自动被写入。如果在一个输出终端上打印了一行的一部分，然后运行了大量的计算后，应当在退出和计算前 fflush(3) 标准输出，使得输出可以显示出来。(?)
标准输入输出库 stdio 是函数库 libc 的一部分，需要时可以被编译器 cc(1) 和 pc(1) 自动加载。下列手册页的 SYNOPSIS 总览 段落会指出要包含哪些文件，函数定义的格式，以及它们受到哪些外部变量的影响。
下列为已定义的宏；如果不用 #undef 取消这些名称的当前定义的话，是不能重新使用它们的： BUFSIZ, EOF, FILENAME_MAX, FOPEN_MAX, L_cuserid, L_ctermid, L_tmpnam, NULL, SEEK_END, SEEK_SET, SEE_CUR, TMP_MAX, clearerr, feof, ferror, fileno, fropen, fwopen, getc, getchar, putc, putchar, stderr, stdin, stdout. 另外，还有与这些宏的功能对应的，函数形式的版本 feof, ferror, clearerr, fileno, getc, getchar, putc, 和 putchar ，在显式地取消宏的定义时，可以使用它们。
LIST OF FUNCTIONS 函数列表
- Function 函数
- Description 描述
- clearerr
- 检测并重置流状态
- fclose
- 关闭流
- fdopen
- 打开流
- feof
- 检测并重置流状态
- ferror
- 检测并重置流状态
- fflush
- 刷新流
- fgetc
- 从输入流中获取下一个字符或词
- fgetpos
- 重定位流
- fgets
- 从流中获取一行
- fileno
- 返回流参数的整数形式的描述符
- fopen
- 打开流
- fprintf
- 按照格式输出常规内容
- fpurge
- 刷新流
- fputc
- 向流输出一个字符或词
- fputs
- 向流输出一行
- fread
- 二进制输入/输出
- freopen
- 打开流
- fropen
- 打开流
- fscanf
- 按照格式输入常规内容
- fseek
- 重定位流
- fsetpos
- 重定位流
- ftell
- 重定位流
- fwrite
- 二进制输入/输出
- getc
- 从输入流中获取下一个字符或词
- getchar
- 从输入流中获取下一个字符或词
- gets
- 从流中获取一行
- getw
- 从输入流中获取下一个字符或词
- mktemp
- 创建 (***的) 临时文件名
- perror
- 系统错误消息
- printf
- 按照格式输出常规内容
- putc
- 向流输出一个字符或词
- putchar
- 向流输出一个字符或词
- puts
- 向流输出一行
- putw
- 向流输出一个字符或词
- remove
- 删除目录项
- rewind
- 重定位流
- scanf
- 按照格式输入常规内容
- setbuf
- 流缓冲操作
- setbuffer
- 流缓冲操作
- setlinebuf
- 流缓冲操作
- setvbuf
- 流缓冲操作
- sprintf
- 按照格式输出常规内容
- sscanf
- 按照格式输入常规内容
- strerror
- 系统错误消息
- sys_errlist
- 系统错误消息
- sys_nerr
- 系统错误消息
- tempnam
- 临时文件控制
- tmpfile
- 临时文件控制
- tmpnam
- 临时文件控制
- ungetc
- 向输入流中退回字符
- vfprintf
- 按照格式输出常规内容
- vfscanf
- 按照格式输入常规内容
- vprintf
- 按照格式输出常规内容
- vscanf
- 按照格式输入常规内容
- vsprintf
- 按照格式输出常规内容
- vsscanf
- 按照格式输入常规内容
CONFORMING TO 标准参考
函数库 stdio 遵循 ANSI X3.159-1989 (``ANSI C'') 标准。
SEE ALSO 参见
open(2), close(2), read(2), write(2), stdout(3)
#p#
NAME
stdio - standard input/output library functions
SYNOPSIS
#include <stdio.h>
FILE *stdin;
FILE *stdout;
FILE *stderr;
DESCRIPTION
The standard I/O library provides a simple and efficient buffered stream I/O interface. Input and output is mapped into logical data streams and the physical I/O characteristics are concealed. The functions and macros are listed below; more information is available from the individual man pages.
A stream is associated with an external file (which may be a physical device) by opening a file, which may involve creating a new file. Creating an existing file causes its former contents to be discarded. If a file can support positioning requests (such as a disk file, as opposed to a terminal) then a file position indicator associated with the stream is positioned at the start of the file (byte zero), unless the file is opened with append mode. If append mode is used, it is unspecified whether the position indicator will be placed at the start or the end of the file. The position indicator is maintained by subsequent reads, writes and positioning requests. All input occurs as if the characters were read by successive calls to the fgetc(3) function; all output takes place as if all characters were written by successive calls to the fputc(3) function.
A file is disassociated from a stream by closing the file. Output streams are flushed (any unwritten buffer contents are transferred to the host environment) before the stream is disassociated from the file. The value of a pointer to a FILE object is indeterminate after a file is closed (garbage).
A file may be subsequently reopened, by the same or another program execution, and its contents reclaimed or modified (if it can be repositioned at the start). If the main function returns to its original caller, or the exit(3) function is called, all open files are closed (hence all output streams are flushed) before program termination. Other methods of program termination, such as abort(3) do not bother about closing files properly.
At program startup, three text streams are predefined and need not be opened explicitly --- standard input (for reading conventional input), --- standard output (for writing conventional input), and standard error (for writing diagnostic output). These streams are abbreviated stdin,stdout and stderr. When opened, the standard error stream is not fully buffered; the standard input and output streams are fully buffered if and only if the streams do not to refer to an interactive device.
Output streams that refer to terminal devices are always line buffered by default; pending output to such streams is written automatically whenever an input stream that refers to a terminal device is read. In cases where a large amount of computation is done after printing part of a line on an output terminal, it is necessary to fflush(3) the standard output before going off and computing so that the output will appear.
The stdio library is a part of the library libc and routines are automatically loaded as needed by the compilers cc(1) and pc(1). The SYNOPSIS sections of the following manual pages indicate which include files are to be used, what the compiler declaration for the function looks like and which external variables are of interest.
The following are defined as macros; these names may not be re-used without first removing their current definitions with #undef: BUFSIZ, EOF, FILENAME_MAX, FOPEN_MAX, L_cuserid, L_ctermid, L_tmpnam, NULL, SEEK_END, SEEK_SET, SEE_CUR, TMP_MAX, clearerr, feof, ferror, fileno, fropen, fwopen, getc, getchar, putc, putchar, stderr, stdin, stdout. Function versions of the macro functions feof, ferror, clearerr, fileno, getc, getchar, putc, and putchar exist and will be used if the macros definitions are explicitly removed.
LIST OF FUNCTIONS
- Function
- Description
- clearerr
- check and reset stream status
- fclose
- close a stream
- fdopen
- stream open functions
- feof
- check and reset stream status
- ferror
- check and reset stream status
- fflush
- flush a stream
- fgetc
- get next character or word from input stream
- fgetpos
- reposition a stream
- fgets
- get a line from a stream
- fileno
- return the integer descriptor of the argument stream
- fopen
- stream open functions
- fprintf
- formatted output conversion
- fpurge
- flush a stream
- fputc
- output a character or word to a stream
- fputs
- output a line to a stream
- fread
- binary stream input/output
- freopen
- stream open functions
- fropen
- open a stream
- fscanf
- input format conversion
- fseek
- reposition a stream
- fsetpos
- reposition a stream
- ftell
- reposition a stream
- fwrite
- binary stream input/output
- getc
- get next character or word from input stream
- getchar
- get next character or word from input stream
- gets
- get a line from a stream
- getw
- get next character or word from input stream
- mktemp
- make temporary file name (unique)
- perror
- system error messages
- printf
- formatted output conversion
- putc
- output a character or word to a stream
- putchar
- output a character or word to a stream
- puts
- output a line to a stream
- putw
- output a character or word to a stream
- remove
- remove directory entry
- rewind
- reposition a stream
- scanf
- input format conversion
- setbuf
- stream buffering operations
- setbuffer
- stream buffering operations
- setlinebuf
- stream buffering operations
- setvbuf
- stream buffering operations
- sprintf
- formatted output conversion
- sscanf
- input format conversion
- strerror
- system error messages
- sys_errlist
- system error messages
- sys_nerr
- system error messages
- tempnam
- temporary file routines
- tmpfile
- temporary file routines
- tmpnam
- temporary file routines
- ungetc
- un-get character from input stream
- vfprintf
- formatted output conversion
- vfscanf
- input format conversion
- vprintf
- formatted output conversion
- vscanf
- input format conversion
- vsprintf
- formatted output conversion
- vsscanf
- input format conversion
CONFORMING TO
The stdio library conforms to ANSI X3.159-1989 (``ANSI C'').
SEE ALSO
open(2), close(2), read(2), write(2), stdout(3)
