day14: 文件读写操作

README.md

@@ -19,3 +19,5 @@
 #### day12: 字符串处理函数，const，结构体
 
 #### day13: 结构体，位域，共用体，枚举，链表操作
+
+#### day14: 文件读写操作

day14/d10.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+// 实现读取 filepath 文件的前 top_n 行数据
+void *read_top_line(const char *filepath, int top_n)
+{
+    FILE *f = fopen(filepath, "r");
+    if (NULL == f)
+    {
+        perror("fopen");
+        return NULL;
+    }
+
+    char(*lines)[100] = calloc(top_n, 100);
+    for (int i = 0; i < top_n; i++)
+    {
+        char *flag = fgets(lines[i], 100, f);
+        if (flag == NULL)
+            break;
+    }
+    fclose(f);
+    return lines;
+}
+
+int main()
+{
+    int n = 5;
+    char(*p)[100] = read_top_line("d10.txt", n);
+    for (int i = 0; i < n; i++)
+    {
+        printf("第 %d 行: %s", i + 1, *(p + i));
+    }
+    free(p);
+
+    return 0;
+}

day14/d10.txt

@@ -0,0 +1,6 @@
+hello,world
+张三
+爱唱歌
+lihai
+hahaha
+手机

day14/d11.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+// 文件复制
+int main()
+{
+    FILE *aF = fopen("d11.txt", "r");
+    if (NULL == aF)
+    {
+        perror("fopen");
+        return 1;
+    }
+
+    FILE *bF = fopen("d11_cpy.txt", "w");
+    int c;
+    while ((c = fgetc(aF)) != EOF)
+    {
+        fputc(c, bF);
+    }
+    fclose(aF);
+    fclose(bF);
+    return 0;
+}

day14/d11.txt

@@ -0,0 +1,6 @@
+hello,world
+张三
+爱唱歌
+lihai
+hahaha
+手机

day14/d11_cpy.txt

@@ -0,0 +1,6 @@
+hello,world
+张三
+爱唱歌
+lihai
+hahaha
+手机

day14/d12.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+// 二进制文件复制
+int main()
+{
+    FILE *aF = fopen("d12.jpg", "rb");
+    if (NULL == aF)
+    {
+        perror("fopen");
+        return 1;
+    }
+
+    FILE *bF = fopen("d12_cpy.jpg", "wb");
+    int c;
+    while ((c = fgetc(aF)) != EOF)
+    {
+        fputc(c, bF);
+    }
+    fclose(aF);
+    fclose(bF);
+    return 0;
+}

day14/d13.c

@@ -0,0 +1,36 @@
+// 自定义二进制文件写入
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct
+{
+    int sid;
+    char name[32];
+    int age;
+    char sex[4];
+} STU;
+
+int main()
+{
+    STU s1 = {1, "disen", 20, "男"};
+    STU s2 = {2, "jack", 18, "女"};
+    STU *s3 = malloc(sizeof(STU));
+    s3->sid = 3;
+    strcpy(s3->name, "lily");
+    s3->age = 19;
+    strcpy(s3->sex, "女");
+
+    FILE *f = fopen("d13.txt", "wb");
+    if (NULL == f)
+    {
+        return 1;
+    }
+
+    fwrite(&s1, sizeof(STU), 1, f);
+    fwrite(&s2, sizeof(STU), 1, f);
+    fwrite(&s3, sizeof(STU), 1, f);
+    fclose(f);
+
+    return 0;
+}

day14/d14.c

@@ -0,0 +1,28 @@
+// 自定义二进制文件读取
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct
+{
+    int sid;
+    char name[32];
+    int age;
+    char sex[4];
+} STU;
+
+int main()
+{
+    FILE *f = fopen("d13.txt", "rb");
+    if (NULL == f)
+    {
+        return 1;
+    }
+    STU *s = malloc(sizeof(STU));
+    fread(s, sizeof(STU), 1, f);
+    printf("%d %s %d %s\n", s->sid, s->name, s->age, s->sex);
+    free(s);
+
+    fclose(f);
+
+    return 0;
+}

day14/d15.c

@@ -0,0 +1,42 @@
+// 自定义二进制文件读取
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct
+{
+    int sid;
+    char name[32];
+    int age;
+    char sex[4];
+} STU;
+
+int main()
+{
+    FILE *f = fopen("d13.txt", "rb");
+    if (NULL == f)
+    {
+        return 1;
+    }
+
+    // 让光标移动到文件尾部
+    fseek(f, 0, SEEK_END);
+    long file_size = ftell(f); // 获取文件大小
+    printf("文件大小: %ld B\n", file_size);
+    int stu_num = file_size / sizeof(STU);
+    printf("学生数目: %d 位\n", stu_num);
+
+    fseek(f, 0, SEEK_SET); // 重置光标位置到头
+    for (int i = 0; i < stu_num; i++)
+    {
+        STU *s = calloc(1, sizeof(STU));
+
+        int fx = fread(s, sizeof(STU), 1, f);
+        if (fx != 0)
+            printf("%d %s %d %s\n", s->sid, s->name, s->age, s->sex);
+        free(s);
+    }
+
+    fclose(f);
+
+    return 0;
+}

day14/d2.c

@@ -0,0 +1,15 @@
+// 行缓冲区
+// 写数据时遇到换行符，则刷新缓冲
+// 如果行缓冲不刷新时，则不会输出结果。
+// 因为输出的内容没有遇到换行符（Linux  `\n`）, Window(`\r\n`)。
+
+#include <stdio.h>
+
+int main()
+{
+    printf("Hello World"); // 缓冲区未写满，不会刷新缓冲区，不会输出
+    while (1)
+        ;
+
+    return 0; // 缓冲未写满，不会刷新缓冲区，不会退出程序
+}

day14/d3.c

@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+int main()
+{
+    int i = 0;
+    // 缓冲区一般为 4KB，这里写入 32B，不会刷新缓冲区
+    char m[33] = "disenjackydisenjackydisenjackyab";
+
+    printf("%s", m);
+    fflush(stdout); // 刷新缓冲区，目的是为了让缓冲区中的数据输出到屏幕上
+    while (1)
+        ; // 用来观察程序退出时是否会刷新缓冲区，阻塞程序
+
+    return 0;
+}

day14/d4.c

@@ -0,0 +1,14 @@
+// 程序正常退出也会刷新缓冲区，显示输出
+#include <stdio.h>
+
+int main()
+{
+    int i = 0;
+    // 缓冲区一般为 4KB，这里写入 32B，不会刷新缓冲区
+    char m[33] = "disenjackydisenjackydisenjackyab";
+
+    printf("%s", m);
+    ;
+
+    return 0;
+}

day14/d5.c

@@ -0,0 +1,18 @@
+// 读写文本文件
+#include <stdio.h>
+#include <stdlib.h>
+
+int main()
+{
+    char *f = (char *)malloc(100);
+    FILE *fp = fopen("d5.txt", "w");
+    if (fp == NULL)
+    {
+        perror("fopen");
+        exit(1);
+    }
+    fputs("disen", fp);
+    fclose(fp);
+
+    return 0;
+}

day14/d5.txt

@@ -0,0 +1 @@
+disen

day14/d6.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <string.h>
+
+int main()
+{
+    FILE *f = fopen("d6.txt", "a");
+    // char content[20] = "hello disen";
+    char *m = "小李";
+    int n = fputs(m, f); // 单字符写入
+    printf("已追加内容的结构 n = %d\n", n);
+    fclose(f);
+    return 0;
+}

day14/d6.txt

@@ -0,0 +1 @@
+hello disen

day14/d7.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <string.h>
+
+int main()
+{
+    FILE *f = fopen("d7.txt", "r");
+    char line[100] = "";
+
+    while (fgets(line, 100, f) != NULL)
+    {
+        printf("%s", line);
+    }
+
+    fclose(f);
+    return 0;
+}

day14/d7.txt

@@ -0,0 +1,3 @@
+hello,world
+张三
+爱唱歌

day14/d8.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <string.h>
+
+int main()
+{
+    FILE *f = fopen("d8.txt", "r");
+    fseek(f, 3, SEEK_SET); // SEEK_SET 0
+    char m[7];
+    for (int i = 0; i < 6; i++)
+    {
+        m[i] = (char)fgetc(f);
+    }
+    m[6] = '\0';
+    printf("%s\n", m);
+
+    fclose(f);
+    return 0;
+}

day14/d8.txt

@@ -0,0 +1,3 @@
+hello,world
+张三
+爱唱歌

day14/d9.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <string.h>
+
+int main()
+{
+    FILE *f = fopen("d9.txt", "r");
+
+    int line1_n = 0;
+    while (fgetc(f) != '\n')
+        line1_n++;
+
+    fseek(f, line1_n + 1, SEEK_SET);
+
+    char line2[100];
+    fgets(line2, 100, f);
+    line2[strlen(line2) - 1] = '\0'; // 去掉换行符
+    printf("line2: %s", line2);
+
+    fclose(f);
+    return 0;
+}

day14/d9.txt

@@ -0,0 +1,3 @@
+hello,world
+张三
+爱唱歌