班级有5名学生，每名学生的信息如下：姓名，年龄，语文成绩，数学成绩，外语成绩。Linux编程实现如下功能： 1、通过键盘给这5名学生赋值，并通过调用函数fwrite或write，保存信息到文件student.txt中。 2、从文件student.txt中通过调用fread或read，读取这5名学生的信息，并显示在屏幕上。

以下是实现上述功能的C代码示例：

#include <stdio.h>
#include <stdlib.h>

typedef struct {
    char name[20];
    int age;
    float chineseScore;
    float mathScore;
    float englishScore;
} Student;

void inputStudentInfo(Student* student) {
    printf("请输入学生姓名：");
    scanf("%s", student->name);
    printf("请输入学生年龄：");
    scanf("%d", &(student->age));
    printf("请输入学生语文成绩：");
    scanf("%f", &(student->chineseScore));
    printf("请输入学生数学成绩：");
    scanf("%f", &(student->mathScore));
    printf("请输入学生英语成绩：");
    scanf("%f", &(student->englishScore));
}

void saveToFile(Student* students, int count) {
    FILE* file = fopen("student.txt", "wb");
    if (file == NULL) {
        printf("保存文件失败\n");
        return;
    }
    
    fwrite(&count, sizeof(int), 1, file);
    fwrite(students, sizeof(Student), count, file);
    
    fclose(file);
}

void readFromFile(Student** students, int* count) {
    FILE* file = fopen("student.txt", "rb");
    if (file == NULL) {
        printf("读取文件失败\n");
        return;
    }
    
    fread(count, sizeof(int), 1, file);
    
    *students = (Student*)malloc((*count) * sizeof(Student));
    fread(*students, sizeof(Student), *count, file);
    
    fclose(file);
}

void printStudentInfo(Student* students, int count) {
    printf("学生信息:\n");
    for (int i = 0; i < count; i++) {
        printf("姓名：%s\n", students[i].name);
        printf("年龄：%d\n", students[i].age);
        printf("语文成绩：%.2f\n", students[i].chineseScore);
        printf("数学成绩：%.2f\n", students[i].mathScore);
        printf("英语成绩：%.2f\n", students[i].englishScore);
        printf("\n");
    }
}

int main() {
    Student students[5];
    int count = 5;
    
    // 输入学生信息
    for (int i = 0; i < count; i++) {
        printf("请输入第%d名学生的信息：\n", i + 1);
        inputStudentInfo(&students[i]);
        printf("\n");
    }
    
    // 保存信息到文件
    saveToFile(students, count);
    
    // 从文件中读取信息并显示
    Student* readStudents;
    int readCount;
    readFromFile(&readStudents, &readCount);
    printStudentInfo(readStudents, readCount);
    
    free(readStudents);
    
    return 0;
}

你可以将此代码保存为`student.c`，然后在Linux终端中使用以下命令编译运行：

gcc student.c -o student
./student

程序将提示您输入学生的信息，然后将信息保存到`student.txt`文件中。接着，它将从该文件中读取学生信息并在屏幕上显示出来。