Linux C,文件读写函数

C标准库提供的用于读写文件的函数非常多，大多数函数都在stdio.h中声明.

fread/fwrite，fgets/fputs，fgetchar/fputchar，fprintf/fscanf.............

这些函数原型声明都在stdio.h中,如下：

size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);

size_t fwrite(const void *ptr, size_t size, size_t nmemb,FILE *stream);

int fgetc(FILE *stream);

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

int getc(FILE *stream);

int getchar(void);

int ungetc(int c, FILE *stream);

无论是写入文件还是从文件流流中读取，都要先打开文件，完成后还要将打开的文件关闭。

为了防止指针变成野指针，还应将文件指针指向NULL。

FILE *fopen(const char *pathname, const char *mode);

FILE *fdopen(int fd, const char *mode);

FILE *freopen(const char *pathname, const char *mode, FILE *stream);

fopen函数的安全版本是fopen_s(FILE *stream,char *filename,char *mode),使用之前要将宏

fileutil.h

 1 #ifndef __FILEUTIL_H
 2
 3 #define __FILEUTIL_H
 4
 5 #include <stdio.h>
 6
 7 FILE *open_file(const char *file,const char *mode);
 8
 9 void read0(const char *file);
10
11 void read1(const char *file);
12
13 void read2(const char *file);
14
15 void write1(const char *file);
16
17 #endif

fileutil.c

  1 /*
  2
  3  * =====================================================================================
  4
  5  *       Filename:  fileutil.c
  6
  7  *    Description:
  8
  9  *        Version:  1.0
 10
 11  *        Created:  2017年04月13日 09时38分23秒
 12
 13  *       Revision:  none
 14
 15  *       Compiler:  gcc
 16
 17  *         Author:  YOUR NAME (),
 18
 19  *   Organization:
 20
 21  * =====================================================================================
 22
 23  */
 24
 25 #include <stdio.h>
 26
 27 #include <stdlib.h>
 28
 29 #include <string.h>
 30
 31 #include "fileutil.h"
 32
 33
 34
 35 FILE *
 36
 37 open_file(const char *file,const char *mode)
 38
 39 {
 40
 41  FILE *fp;
 42
 43  if(!(fp = fopen(file,mode))){
 44
 45  perror("open file error");
 46
 47  exit(-1);
 48
 49  }
 50
 51  return fp;
 52
 53 }
 54
 55
 56
 57 void read0(const char *file)
 58
 59 {
 60
 61  FILE *fp = open_file(file,"r");
 62
 63  char buf[BUFSIZ] = {0};
 64
 65  unsigned long t = 0;
 66
 67  //int tmp = fread(buf,1,20,fp);
 68
 69  //printf("read %d bytes\n",tmp);
 70
 71  //printf("read buf from %s is %s\n",file,buf);
 72
 73  while((t = fread(buf,1,192,fp)) != 0){
 74
 75  printf("%s\n",buf);
 76
 77  bzero(&buf,sizeof(buf));
 78
 79  }
 80
 81  if(fclose(fp) != 0) perror("close file error");
 82
 83 }
 84
 85
 86
 87 void read1(const char *file)
 88
 89 {
 90
 91  FILE *fp = open_file(file,"r");
 92
 93  char *buf;
 94
 95  size_t n = 0;
 96
 97  while((n = getline(&buf,&n,fp)) != (size_t)-1){
 98
 99  printf("%s",buf);
100
101  bzero(buf,sizeof(buf));
102
103  }
104
105  //if(buf) free(buf);
106
107  if(fclose(fp) != 0) perror("close file error");
108
109 }
110
111
112
113 void read2(const char *file)
114
115 {
116
117  FILE *fp = open_file(file,"r");
118
119  char buf[BUFSIZ] = "";
120
121  while(fgets(buf,BUFSIZ,fp)){
122
123  printf("%s",buf);
124
125  bzero(buf,BUFSIZ);
126
127  }
128
129  if(fclose(fp) != 0) perror("close file error");
130
131 }
132
133
134
135 /* 尚未实现 */
136
137 void write1(const char *file)
138
139 {
140
141  FILE *fp = open_file(file,"a+t");
142
143  if(fclose(fp) != 0) perror("close file error");
144
145 }