標準c的io操作

1. io操作執行個體

2. io函數分析

<1>. io 操作執行個體 

1.1  文字檔讀取

#include <stdio.h>// file io operators#include <stdlib.h>int main(int argc, char* argv[]){FILE* fp;int ch;long int count = 0;if (argc != 2){ printf("usage : %s filename", argv[0]); return EXIT_SUCCESS;}// open fileif ( (fp = fopen(argv[1], "r")) == NULL ){ printf("can not open the file\n"); return EXIT_FAILURE;}while ( (ch = getc(fp)) != EOF ){ printf("%c", ch); count++;}// close filefclose(fp);// print how many chars in the fileprintf("the file has %ld chars\n", count);return EXIT_SUCCESS;}

1.2 二進位檔案讀取

/* * file_op.c * *  Created on: Apr 19, 2011 *      Author: xuqiang */#include <stdio.h>#include <stdlib.h>#include "file_op.h"void randbin(){const int NUMBER_SIZE = 1000;double numbers[NUMBER_SIZE];double read_numbers[NUMBER_SIZE];const char* file = "number.dat";long pos;FILE* fp;int index;double value;// make a random arrayint i;for (i = 0; i < NUMBER_SIZE; ++i){ numbers[i] = i;}// open fileif ( (fp =  fopen(file, "wb")) == NULL ){ printf("error to open the file for writing\n"); exit(1);}// write the data to filefwrite(numbers, sizeof(double), NUMBER_SIZE,fp);fclose(fp);// open the file for readif ( (fp = fopen(file, "rb")) == NULL ){ printf("error open the file for read\n"); exit(1);}printf("enter a index from 0 to %d :", NUMBER_SIZE - 1);scanf("%d", &index);pos = index * sizeof(double);fseek(fp, pos, SEEK_SET);fread(&value, sizeof(double), 1, fp);printf("the number is %f\n", value);fclose(fp);printf("done\n");exit(0);} <2>. io 函數分析 

下面是在我的ubuntu上的<stdio.h>檔案比較重要函數:

/* End of file character. 定義檔案結尾   Some things throughout the library rely on this being -1.  */#ifndef EOF# define EOF (-1)

#endif 

/* The possibilities for the third argument to `fseek'. 定義在fseek函數中使用的產量   These values should not be changed.  */#define SEEK_SET0/* Seek from beginning of file.檔案開始  */#define SEEK_CUR1/* Seek from current position.當前檔案指標位置  */

#define SEEK_END2/* Seek from end of file. 檔案結尾 */

 /* Rename file OLD to NEW. 重新命名檔案 */

extern int rename (__const char *__old, __const char *__new) __THROW;/* Close STREAM.關閉檔案流   This function is a possible cancellation point and therefore not   marked with __THROW.  */

extern int fclose (FILE *__stream); 

/* Flush STREAM, or all streams if STREAM is NULL.重新整理緩衝區，如果參數為null的話，將重新整理所有的緩衝區   This function is a possible cancellation point and therefore not   marked with __THROW.  */

extern int fflush (FILE *__stream); 

/* 開啟檔案，__filename帶開啟的檔案名稱， __modes開啟檔案，例如讀寫*/ 

extern FILE *fopen (__const char *__restrict __filename,

   __const char *__restrict __modes) __wur; 

/* If BUF is NULL, make STREAM unbuffered.更改標準io的緩衝方式   Else make it use buffer BUF, of size BUFSIZ.  */

extern void setbuf (FILE *__restrict __stream, char *__restrict __buf) __THROW; 

 /* If BUF is NULL, make STREAM unbuffered.

   Else make it use SIZE bytes of BUF for buffering.  */extern void setbuffer (FILE *__restrict __stream, char *__restrict __buf,       size_t __size) __THROW;/* Make STREAM line-buffered. 設定成行緩衝方式 */extern void setlinebuf (FILE *__stream) __THROW;/* Write formatted output to S. 一個比較常用的函數，格式化一個字串，類似於c#中的String.Format */extern int sprintf (char *__restrict __s,

   __const char *__restrict __format, ...) __THROW; 

/* Maximum chars of output to write in MAXLEN. 和函數sprintf類似，但是更加安全，增加了__maxlen參數 */extern int snprintf (char *__restrict __s, size_t __maxlen,

    __const char *__restrict __format, ...) 

/* Read a character from STREAM.從流中讀取字元   These functions are possible cancellation points and therefore not   marked with __THROW.  */extern int fgetc (FILE *__stream);

extern int getc (FILE *__stream); 

/* Write a character to STREAM.向流中寫入字元   These functions are possible cancellation points and therefore not   marked with __THROW.   These functions is a possible cancellation point and therefore not   marked with __THROW.  */extern int fputc (int __c, FILE *__stream);

extern int putc (int __c, FILE *__stream); 

 

/* Get a newline-terminated string of finite length from STREAM.讀取一行，s為開始指標，n為緩衝長度   This function is a possible cancellation point and therefore not   marked with __THROW.  */extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream)     __wur;

/* 向流中寫入字串 */ 

extern int fputs (__const char *__restrict __s, FILE *__restrict __stream); 

/* Push a character back onto the input buffer of STREAM.向流中回退一個字元   This function is a possible cancellation points and therefore not   marked with __THROW.  */

extern int ungetc (int __c, FILE *__stream); 

/***************************二進位讀取寫入******************************************/ 

/* Read chunks of generic data from STREAM.   This function is a possible cancellation points and therefore not   marked with __THROW.  */extern size_t fread (void *__restrict __ptr, size_t __size,     size_t __n, FILE *__restrict __stream) __wur;/* Write chunks of generic data to STREAM.ptr讀取緩衝區開始位置，size：單位的長度，n讀取數量   This function is a possible cancellation points and therefore not   marked with __THROW.  */extern size_t fwrite (__const void *__restrict __ptr, size_t __size,

     size_t __n, FILE *__restrict __s); 

/********************************流指標操作**************************************/

/* Seek to a certain position on STREAM.   This function is a possible cancellation point and therefore not   marked with __THROW.  */extern int fseek (FILE *__stream, long int __off, int __whence);/* Return the current position of STREAM.   This function is a possible cancellation point and therefore not   marked with __THROW.  */extern long int ftell (FILE *__stream) __wur;/* Rewind to the beginning of STREAM.將流指標回到檔案開始   This function is a possible cancellation point and therefore not   marked with __THROW.  */

extern void rewind (FILE *__stream); 

/*****************************另外和檔案鎖相關的函數************************************/