读写操作

#include "stdio.h"

void readFileTest();

void writeFileTest();

void copyTest();



//TODO 文件读写
int main(int argc,char **argv) {

//    readFileTest();
//    writeFileTest();
//  copyTest();

    printf("argc = %d\n",argc);
    if(argv){
        printf("argv=%c\n",argv);
    }

    if(argv < 3) return 0;
    FILE *pr = fopen(argv[1], "r");
    if(pr == NULL) return 0;
    FILE *pw = fopen(argv[2], "w");
    if(pw == NULL) return 0;
    if (pw) {
        while (1){
            char c = fgetc(pr);
            if(c == EOF){
                break;
            }
            fputc(c,pw);
        }
        fclose(pw);
        pw = NULL;
    }
    fclose(pr);
    pr = NULL;

    return 0;
}





void readFileTest() {
    FILE *p = fopen("../src/test/a.txt", "r");
    if (p) {
        printf("success\n");
        while (1) {
            char c = fgetc(p);
            if (c == EOF) {
                break;
            }
            printf("%c", c);
        }
        fclose(p);
        p = NULL;
    } else {
        printf("fail\n");
    }
}

void writeFileTest() {
    printf("success\n");

    FILE *p = fopen("../src/test/a.txt", "a");
    if (p) {
        fputc('0',p);
        fclose(p);
        p = NULL;
    }


}

void copyTest() {
    printf("copy open success\n");

    FILE *pr = fopen("../src/test/a.txt", "r");
    if(pr == NULL) return;
    FILE *pw = fopen("../src/test/a1.txt", "w");
    if(pr == NULL) return;
    if (pw) {
        while (1){
            char c = fgetc(pr);
            if(c == EOF){
                break;
            }
            fputc(c,pw);
        }
        fclose(pw);
        pw = NULL;
    }
    fclose(pr);
    pr = NULL;
}

文件加解密思路：

#include "stdio.h"

void file_opt();

void file_tpo();

int main(int argc,char **argv) {
//    file_opt();
//    file_tpo();

    printf("加解密，0加密，1解密\n");
    if(argv<4) return 0;
    FILE *pr = fopen(argv[1],"r");
    if(pr == NULL) return 0;
    FILE *pw = fopen(argv[2],"w");
    if(pw){
        char key = argv[3][0];
        printf("key:%d\n",key);
        char c = getc(pr);

        while (c!=EOF) {
            if(key == '0'){
                c++;
            }else {
                c--;
            }
            putc(c, pw);
            c = fgetc(pr);
        }
        fclose(pw);
        pw = NULL;
    }

    fclose(pr);
    pr = NULL;


    return 0;

}

void file_opt() {
    printf("\n");
    FILE *pr = fopen("../src/test/a.txt", "r");
    if (pr == NULL) return;
    FILE *pw = fopen("../src/test/b.txt", "w");
    if (pw) {
        while (1) {
            char c = fgetc(pr);
            if (c == EOF) {
                break;
            }
            c++;
            fputc(c, pw);
        }
        fclose(pw);
        pw = NULL;
    }
    fclose(pr);
    pr = NULL;
}

void file_tpo() {
    printf("\n");
    FILE *pr = fopen("../src/test/b.txt", "r");
    if (pr == NULL) return;
    FILE *pw = fopen("../src/test/c.txt", "w");
    if (pw) {
        while (1) {
            char c = fgetc(pr);
            if (c == EOF) {
                break;
            }
            c--;
            fputc(c, pw);
        }
        fclose(pw);
        pw = NULL;
    }
    fclose(pr);
    pr = NULL;
}

小例子

文本内容，简单的公示，算出结果,并且讲解写回去

1+2=
2*3=
4-1=
5/2=

#include "stdio.h"
#include "stdlib.h"

int calc(int a, char b, int c);


void calResult();
void calResultCall();

int main(int argc, char **argv) {
//    calResult();
    calResultCall();

    return 0;

}

void calResultCall() {
    FILE *pr = fopen("../src/test/cal.txt", "r");
    if (pr) {
        char * array  = calloc(100, sizeof(char));
        char * tmp = array;// 当前位置
        int index = 0;
        while(1){
            if(feof(pr)) break;
            char buf[100] = {0};
            fgets(buf, sizeof(buf), pr);
            int a = 0, c = 0;
            char b = 0;
            sscanf(buf,"%d%c%d=",&a,&b,&c);

            int result = calc(a,b,c);
            // 缓存起来
            sprintf(tmp,"%d%c%d=%d\n",a,b,c,result);
            array = realloc(array,100 * (index+2));
            tmp = array + 100*(index + 1);

            index++;
            printf("%d%c%d=%d\n",a,b,c,result);
        }


        fclose(pr);

        // 写回去
        pr = fopen("../src/test/cal.txt", "w");
        int i;
        tmp = array;
        for (i = 0; i < index; ++i) {
            fputs(tmp,pr);
            tmp += 100;
        }
        free(array);
        pr = NULL;
    }
}

void calResult() {
    FILE *pr = fopen("../src/test/cal.txt", "r");
    if (pr) {

        while(1){
            if(feof(pr)) break;
            char buf[100] = {0};
            fgets(buf, sizeof(buf), pr);
            int a = 0, c = 0;
            char b = 0;
            sscanf(buf,"%d%c%d=",&a,&b,&c);
            int result = calc(a,b,c);
            printf("%d%c%d=%d\n",a,b,c,result);
        }


        fclose(pr);
        pr = NULL;
    }
}

int calc(int a, char b, int c) {
    switch (b) {
        case '+':
            return a + c;
        case '-':
            return a - c;
        case '*':
            return a * c;
        case '/':
            return a / c;
    }
    return 0;
}

拷贝文件工具实例

#include "stdio.h"
#include "stdlib.h"
#include "sys/stat.h"

#define  BLOCK_SIZE  1024 * 64//定义阈值每次最多读取

int main(int argc, char **argv) {
    printf("\n");
    if (argc < 3) {
        return 0;
    }

    FILE *pr = fopen(argv[1], "rb");
    if (pr == NULL) return 0;
    FILE *pw = fopen(argv[2], "wb");
    // 获取文件大小
    struct stat st = {0};
    stat(argv[1], &st);
    int size = st.st_size;
    printf("size= %d\n", size);

    if (size > BLOCK_SIZE) {
        size = BLOCK_SIZE;
    }
    char *buf = calloc(1, size);
    unsigned int index = 0;

    while (!feof(pr)) {
        // 按照block读写
        int res = fread(buf, 1, size, pr);
        fwrite(buf, 1, res, pw);
        index++;
    }

    free(buf);

    fclose(pw);
    fclose(pr);
    printf("index=%d",index);
    return 0;

}
-> 测试
 gcc a file_demo4.c -o cp.exe
./cp.exe ../src/test/demo.mp4 ../src/test/temp.mp4 

fflush 方法慎用

#include "stdio.h"
#include "stdlib.h"
int main(int argc,char **argv) {
    FILE *pr = fopen("../src/test/flush.txt", "w");
    if (pr) {

        while(1){
            printf("please input:\n");
            char buf[100] = {0};
            scanf("%s",buf);
            if(strcmp(buf,"exit") == 0) {
                break;
            }
            fputs(buf,pr);
//            fflush(pr);// 除非及时保存一般不用
        }

        fclose(pr);
        pr = NULL;
    }
    return 0;
}