嵌入式学习——Linux操作系统——文件编程练习

1.使用fread和fwrite方式完成任意普通文件的拷贝功能。
模拟 文件下载

#include <stdio.h>void do_copy(FILE *fp_s,FILE *fp_d)
{char buf[100] = {0};int ret;while (ret = fread(buf,sizeof(char),sizeof(buf),fp_s))fwrite(buf,sizeof(char),ret,fp_d);
}//./a.out src dest 
int main(int argc, const char *argv[])
{if (argc != 3){printf("Usage: %s <src> <dest>\n",argv[0]);return -1;}FILE *fp_s = fopen(argv[1],"r");FILE *fp_d = fopen(argv[2],"w");if (fp_s == NULL || fp_d == NULL){perror("fopen fail");return -1;}//创建空洞文件 fseek(fp_s,0,SEEK_END);long len = ftell(fp_s);//1.偏移 fseek(fp_d,len-1,SEEK_SET);//2.写 fputc('\0',fp_d);fflush(fp_d);//	getchar();rewind(fp_s);rewind(fp_d);do_copy(fp_s,fp_d);fclose(fp_s);fclose(fp_d);return 0;
}

#include <stdio.h>
#include <stdlib.h>//./a.out src dest 
int main(int argc, const char *argv[])
{if (argc != 3){printf("Usage: %s <src> <dest>\n",argv[0]);return -1;}FILE *fp_s = fopen(argv[1],"r");FILE *fp_d = fopen(argv[2],"w");if (fp_s == NULL || fp_d == NULL){perror("fopen fail");return -1;}//创建空洞文件 fseek(fp_s,0,SEEK_END);long len = ftell(fp_s);//1.偏移 fseek(fp_d,len-1,SEEK_SET);//2.写 fputc('\0',fp_d);fflush(fp_d);//	getchar();rewind(fp_s);rewind(fp_d);//	do_copy(fp_s,fp_d);char *buf = malloc(len);int ret = fread(buf,sizeof(char),len,fp_s);fwrite(buf,sizeof(char),ret,fp_d);fclose(fp_s);fclose(fp_d);return 0;
}

//1.打开
创建空洞文件
//2.拷贝
//3.关闭

2.实现插入功能，
指定要插入的位置 (如100个字节之后，)
指定要插入的内容 (如hello)
则最终效果是将 hell插入到了100个字节的后面


hello
a.定位到要插入的位置
后面的数据读走
b.重新定位到要插入的位置
输入数据
c.将刚才读走的数据写到插入数据的后面
 

#include <stdio.h>
#include <string.h>int main(int argc, const char *argv[])
{if (argc!= 2){printf("Usage: %s <file>\n",argv[0]);return -1;}FILE *fp = fopen(argv[1],"r+");if (fp == NULL){perror("fopen fail");return -1;}printf("Input a offset:");int offset;scanf("%d",&offset);getchar();printf("Input a string:");char buf[100];fgets(buf,sizeof(buf),stdin);buf[strlen(buf)-1] = '\0';fseek(fp,0,SEEK_END);long len = ftell(fp);fseek(fp,offset,SEEK_SET);char buff[len-offset];int ret = fread(buff,sizeof(char),sizeof(buff),fp);fseek(fp,offset,SEEK_SET);fwrite(buf,sizeof(char),strlen(buf),fp);fwrite(buff,sizeof(char),ret,fp);fclose(fp);return 0;
}

3.统计文本文件中a-z，出现的次数。
a:12
b:23
c:
z:34

#include<stdio.h>  int main(int argc, const char *argv[])  
{  if (argc != 2) {  printf("Usage: %s <filename>\n", argv[0]);  return 1;  }  FILE *fp = fopen(argv[1], "r");  if (fp == NULL) {  perror("Error opening file");  return 1;  }  int a[26] = {0};  char b;  while ((b = fgetc(fp)) != EOF)  {  if (b >= 'a' && b <= 'z')  {  a[b - 'a']++;  }  }  int i = 0;  for (i = 0; i < 26; ++i)  {  printf("%c:%d\n", 'a' + i, a[i]);  }  fclose(fp);  return 0;  
}

4. 完成两个文件的合并操作。
./a.out 1.txt 2.txt 3.txt

#include<stdio.h>  int main(int argc, const char *argv[])  
{  if (argc != 4) {  printf("Usage: %s <filename><filename><filename>\n", argv[0]);  return -1;  }  FILE *fp1 = fopen(argv[1], "r"); FILE *fp2 = fopen(argv[2], "r"); FILE *fp3 = fopen(argv[3], "a+"); if (fp1 == NULL||fp2 == NULL ||fp3 == NULL) {  perror("Error opening file");  return -1;  }  char buf1[1024];char buf2[1024];int num1 = fread(buf1,1,sizeof(buf1),fp1);fwrite(buf1,1,num1,fp3);int num2 = fread(buf2,1,sizeof(buf2),fp2);fseek(fp3,num1,SEEK_SET);fwrite(buf2,1,num2,fp3);fclose(fp1);fclose(fp2);fclose(fp3);return 0;  
}