C applet - file operation, C program read and write files, configuration file read and write cases

1. File operations

(1) Write the file by character

#define  _CRT_SECURE_NO_WARNINGS 
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

void main()
{
    int     i = 0;
    FILE *fp = NULL;
    char *filename2 = "c:/2.txt";  
    char a[27] = "dsadsadefsfdggsfadqw";
    fp = fopen(filename2, "r+"); //读写的方式，打开文件 如果文件不存在，则报错
    if (fp == NULL)
    {
        printf("func fopen() err:%d \n");
        return;
    }
    printf("打开成功\n");

    for (i = 0; i < strlen(a); i++)
    {
        fputc(a[i], fp);
    }

    printf("写入成功\n");

    fclose(fp);

    printf("hello...\n");
    system("pause");
    return;
}

• 

(2) Read the file by character

#define  _CRT_SECURE_NO_WARNINGS 
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

void main()
{
    int     i = 0;
    FILE *fp = NULL;
    char *filename2 = "c:/2.txt"; 
    fp = fopen(filename2, "r+");//读写的方式，打开文件 如果文件不存在，则报错
    if (fp == NULL)
    {
        printf("func fopen() err:%d \n");
        return;
    }
    printf("打开成功\n");

    while (!feof(fp))
    {
        char tempc = fgetc(fp);
        printf("%c", tempc);

    }
    printf("\n读取成功\n");
    if (fp != NULL)
    {
        fclose(fp);
    }

    printf("hello...\n");
    system("pause");
    return;
}

• 

(4) Read the file line by line

#define  _CRT_SECURE_NO_WARNINGS 
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

void main()
{
    int     i = 0;
    FILE *fp = NULL;
    char *filename2 = "c:/22.txt";
    char buf[1024];
    fp = fopen(filename2, "r+");

    if (fp == NULL)
    {
        printf("func fopen() err:%d \n");
        return;
    }
    printf("打开成功\n");

    while (!feof(fp))
    {
        char *p = fgets(buf, 1024, fp); //C 函数库会 一行一行的copy数据到buf指针所指的内存空间中并且变成C风格的字符串
        if (p == NULL)
        {
            goto End;
        }
        printf("%s", buf);
    }
End:
    if (fp != NULL)
    {
        fclose(fp);
    }

    printf("读取成功\n");

    fclose(fp);

    printf("hello...\n");
    system("pause");
    return;
}

• 

(5) Write files in blocks

#define  _CRT_SECURE_NO_WARNINGS 
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

//直接把内存数据写入到文件中
typedef struct Teacher
{
    char name[64];
    int age;
}Teacher;

void main()
{
    int i = 0;
    FILE *fp = NULL;
    char *fileName = "c:/3.data";
    Teacher tArray[3];
    int  myN = 0;

    for (i = 0; i < 3; i++)
    {
        sprintf(tArray[i].name, "%d%d%d", i + 1, i + 1, i + 1);
        tArray[i].age = i + 31;
    }

    fp = fopen(fileName, "wb");
    if (fp == NULL)
    {
        printf("建立文件失败\n");
        return;
    }
    printf("建立文件成功\n");

    for (i = 0; i < 3; i++)
    { 
        // fwrite(_In_count_x_(_Size*_Count) const void * _Str, _In_ size_t _Size, _In_ size_t _Count, _Inout_ FILE * _File);
        //函数参数
        //_Str : 从内存块的开始
        //_Size: 写多长
        //_Count: 写多少次
        //_File : 写入到文件指针所指向的文件中

        //函数的返回值 
        myN = fwrite(&tArray[i], sizeof(Teacher), 1, fp);

        //myN 用于判断有没有写满磁盘

    }
    printf("写入成功\n");

    if (fp != NULL)
    {
        fclose(fp);
    }

    printf("hello...\n");
    system("pause");
    return;
}

• 

(6) Read the file in blocks

#define  _CRT_SECURE_NO_WARNINGS 
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

typedef struct Teacher
{
    char name[64];
    int age;
}Teacher;

void main()
{
    int i = 0;
    FILE *fp = NULL;
    char *fileName = "c:/3.data";
    Teacher tArray[3];
    int  myN = 0;

    fp = fopen(fileName, "r+b");
    if (fp == NULL)
    {
        printf("建立文件失败\n");
        return;
    }
    for (i = 0; i < 3; i++)
    {
        // fread(_Out_bytecap_x_(_ElementSize*_Count) void * _DstBuf, _In_ size_t _ElementSize, _In_ size_t _Count, _Inout_ FILE * _File);
        myN = fread(&tArray[i], sizeof(Teacher), 1, fp);
    }

    for (i = 0; i < 3; i++)
    {
        printf("name:%s, age:%d \n", tArray[i].name, tArray[i].age);
    }

    if (fp != NULL)
    {
        fclose(fp);
    }

    printf("hello...\n");
    system("pause");
    return;
}

• 
  

2. Configuration file read and write case

1. Requirements

• 1). Configuration file read (according to the key, read the value, and print it out)
• 2). Configuration file writing (input key, value)
• 3). Configuration file modification (input key, value)
• 4). Optimization ==> interface, module

2. Implementation steps

• 1). Write a header file my.h (write interface)
• 2). Write a source file cfg.c (to implement read and write operations)
• 3). Write a source file test.c (for testing the code)
• 4). Write a configuration file mycfg.ini

3. Header file my.h code

#ifndef __MY__
#define __MY__

#ifdef  __cplusplus
extern "C" {
#endif

//获取配置项
int GetCfgItem(char *pFileName /*in*/, char *pKey /*in*/, char * pValue/*in out*/, int * pValueLen /*out*/);

//写配置项 
int WriteCfgItem(char *pFileName /*in*/, char *pItemName /*in*/, char *pItemValue/*in*/, int itemValueLen /*in*/);

#ifdef  __cplusplus
}
#endif

#endif

• 
  

4. Source file cfg.c code

#define  _CRT_SECURE_NO_WARNINGS 
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#define MaxLine 2048 //最大行数

//获取配置项
int GetCfgItem(char *pFileName /*in*/, char *pKey /*in*/, char * pValue/*in out*/, int * pValueLen /*out*/)
{

    int     ret = 0;
    FILE    *fp = NULL;
    char    *pTmp = NULL, *pEnd = NULL, *pBegin = NULL;

    char lineBuf[MaxLine];

    fp = fopen(pFileName, "r");
    if (fp == NULL)
    {
        ret = -1;
        return ret;
    }

    while (!feof(fp))
    {
        memset(lineBuf, 0, sizeof(lineBuf));
        //fgets(_Out_z_cap_(_MaxCount) char * _Buf, _In_ int _MaxCount, _Inout_ FILE * _File);
        fgets(lineBuf, MaxLine, fp);
        //printf("lineBuf:%s ",lineBuf );

        pTmp = strchr(lineBuf, '='); 
        if (pTmp == NULL) //如果此行没有=号，跳下一行
        {
            continue;
        }

        pTmp = strstr(lineBuf, pKey);
        if (pTmp == NULL) //判断key是不是在所在行
        {
            continue;
        }
        pTmp = pTmp + strlen(pKey); //mykey1 = myvalude1 ==> "= myvalude1"

        //可能key与=号之间有空格，此时可以直接去找=号
        pTmp = strchr(pTmp, '=');
        if (pTmp == NULL) //在判断有没有=号
        {
            continue;
        }
        pTmp = pTmp + 1;

        //获取value起点
        while (1) 
        {
            if (*pTmp == ' ')
            {
                pTmp ++ ;
            } 
            else
            {
                pBegin = pTmp;
                if (*pBegin == '\n')
                {
                    //没有配置value
                    //printf("配置项:%s 没有配置value \n", pKey);
                    goto End;
                }
                break;
            }
        }

        //获取valude结束点
        while (1) 
        {
            if ((*pTmp == ' ' || *pTmp == '\n'))
            {
                break;
            }
            else 
            {
                pTmp ++;
            }
        }
        pEnd = pTmp;

        //赋值，此时就去除了前后的空格
        *pValueLen = pEnd-pBegin;
        memcpy(pValue, pBegin, pEnd-pBegin);
    }

End:
    if (fp == NULL)
    {
        fclose(fp);
    }
    return 0;

}

//写配置项 
//实现流程
//循环读每一行，检查key配置项是否存在 若存在修改对应value值
//若不存在，在文件末尾 添加 "key = value"
int WriteCfgItem(char *pFileName /*in*/, char *pKey /*in*/, char * pValue/*in*/, int ValueLen /*in*/)
{
    int     rv = 0, iTag = 0, length = 0;
    FILE    *fp = NULL;
    char    lineBuf[MaxLine];
    char    *pTmp = NULL, *pBegin = NULL, *pEnd = NULL;
    char    filebuf[1024*8] = {0};

    if (pFileName==NULL || pKey==NULL || pValue==NULL) 
    {
        rv = -1;
        printf("SetCfgItem() err. param err \n");
        goto End;
    }
    //打开文件
    fp = fopen(pFileName, "r+");
    if (fp == NULL)
    {
        rv = -2;
        printf("fopen() err. \n");
    }

    if (fp == NULL)
    {
        //如果文件不存在，则建一个文件（为了友好）
        fp = fopen(pFileName, "w+t");
        if (fp == NULL)
        {
            rv = -3;
            printf("fopen() err. \n");
            goto End;
        }
    }

    fseek(fp, 0L, SEEK_END); //把文件指针从0位置开始，移动到文件末尾
    //获取文件长度;
    length = ftell(fp);

    fseek(fp, 0L, SEEK_SET);

    if (length > 1024*8) 
    {
        rv = -3;
        printf("文件超过1024*8, nunsupport");
        goto End;
    }

    while (!feof(fp))
    {
        //读每一行
        memset(lineBuf, 0, sizeof(lineBuf));
        pTmp = fgets(lineBuf, MaxLine, fp);
        if (pTmp == NULL) 
        {
            break;
        }

        //key关键字是否在本行
        pTmp = strstr(lineBuf, pKey);
        if (pTmp == NULL) //key关键字不在本行， copy到filebuf中
        {
            strcat(filebuf, lineBuf);
            continue;
        }
        else  //key关键字在本行中，替换旧的行，再copy到filebuf中 
        {
            sprintf(lineBuf, "%s = %s\n", pKey, pValue);  
            strcat(filebuf, lineBuf);
            //若存在key
            iTag = 1; 
        }
    }

    //若key关键字，不存在追加
    if (iTag == 0) 
    {
        fprintf(fp, "%s = %s\n", pKey, pValue);
    }
    else //若key关键字，存在，则重新创建文件
    {
        if (fp != NULL) 
        { 
            fclose(fp); 
            fp = NULL; //避免野指针
        }

        fp = fopen(pFileName, "w+t"); 
        if (fp == NULL)
        {
            rv = -4;
            printf("fopen() err. \n");
            goto End;
        }
        fputs(filebuf, fp);
    }
End:
    if (fp != NULL)
    {
        fclose(fp); 
    }
    return rv;
}

• 
  

5. Source file test.c code

#define  _CRT_SECURE_NO_WARNINGS 
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "my.h"

#define CFGNAME "c:/mycfg.ini"
void mymenu()
{
    printf("=============================\n");
    printf("1 写配置文件\n");
    printf("2 读配置文件\n");
    printf("0 退出\n");
    printf("=============================\n");
}

//读配置项
int TGetCfg()
{
    int     ret = 0;
    char    name[1024] = {0};
    char    value1[1024] = { 0 };
    int     vlen = 0;

    printf("\n请键入key:");
    scanf("%s", name);

    ret = GetCfgItem(CFGNAME /*in*/, name /*in*/, value1/*in*/, &vlen);
    if (ret != 0)
    {
        printf("func WriteCfgItem err:%d \n", ret);
        return ret;
    }
    printf("value:%s \n", value1);

}

//写配置项 
int TWriteCfg()
{
    int     ret = 0;

    char name[1024] = {0};
    char value1[1024] = {0};


    printf("\n请键入key:");
    scanf("%s", name);

    printf("\n请键入value:");
    scanf("%s", value1);

    ret = WriteCfgItem(CFGNAME /*in*/, name /*in*/, value1/*in*/, strlen(value1) /*in*/);
    if (ret != 0)
    {
        printf("func WriteCfgItem err:%d \n", ret);
        return ret;
    }
    printf("你的输入是：%s = %s \n", name, value1);
    return ret;
}

void main()
{

    int choice;

    for (;;)
    {
        //显示一个菜单
        mymenu();
        scanf("%d", &choice);
        switch (choice)
        {       
            case 1:   
                TWriteCfg();//写配置项
                break;
            case 2: 
                TGetCfg(); //读配置项
                break;
            case 0: 
                exit(0);
            default:;
                exit(0);
        }

    }
    printf("hello...\n");
    system("pause");
    return ;
}

• 
  

6. Configuration file mycfg.ini

7. Test Results