C 文件处理基础知识

在这里我们将看到一些在C语言中的基本文件处理操作。以下是这些操作的列表：

• 向文件中写入内容
• 从文件中读取内容
• 在文件中追加内容

向文件中写入内容

请参考以下代码以了解如何向文件中写入内容

示例代码

#include <stdio.h>
int main() {
   FILE *fp;
   char *filename = "sample.txt";
   char *content = "Hey there! You've successfully created a file with content in c programming language.";
   /* open for writing */
   fp = fopen(filename, "w");
   if( fp == NULL ) {
      printf("%s: failed to open. 
", filename);
      return -1;
   } else {
      printf("%s: opened in write mode.
", filename);
   }
   /* Write content to file */
   fprintf(fp, "%s
", content);
   if( !fclose(fp) )
      printf("%s: closed successfully.
", filename);
   return 0;
}

输出

sample.txt: opened in write mode.
sample.txt: closed successfully.

2.从文件中读取

查看代码以了解我们如何从文件中读取 创建一个文件（file_read.txt）：

您使用C编程语言打开了一个只读模式的文件。

示例代码

#include <stdio.h>
int main() {
   FILE *fp;
   char *filename = "file_read.txt";
   char ch;
   /* open for writing */
   fp = fopen(filename, "r");
   if (fp == NULL) {
      printf("%s does not exists 
", filename);
      return;
   } else {
      printf("%s: opened in read mode.
", filename);
   }
   while ((ch = fgetc(fp) )!= EOF) {
      printf ("%c", ch);
   }
   if (!fclose(fp))
      printf("
%s: closed.
", filename);
   return 0;
}

输出

file_read.txt: opened in read mode.
You have opened a file using C programming language, in read-only mode.
file_read.txt: closed.

3.将内容追加到文件中

查看代码以了解如何将行追加到文件中的方法。

创建文件（file_append.txt）

This text was already there in the file.

示例代码

#include <stdio.h>
int main() {
   FILE *fp;
   char ch;
   char *filename = "file_append.txt";
   char *content = "This text is appeneded later to the file, using C programming.";
   /* open for writing */
   fp = fopen(filename, "r");
   printf("
Contents of %s -
", filename);
   while ((ch = fgetc(fp) )!= EOF) {
      printf ("%c", ch);
   }
   fclose(fp);
   fp = fopen(filename, "a");
   /* Write content to file */
   fprintf(fp, "%s
", content);
   fclose(fp);
   fp = fopen(filename, "r");
   printf("
Contents of %s -
", filename);
   while ((ch = fgetc(fp) )!= EOF) {
      printf ("%c", ch);
   }
   fclose(fp);
   return 0;
}

输出

Contents of file_append.txt -
This text was already there in the file.
Appending content to file_append.txt...
Content of file_append.txt after 'append' operation is -
This text was already there in the file.
This text is appeneded later to the file, using C programming.

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