文件是磁盘上的物理存储位置,目录是用于组织文件的逻辑路径。文件存在于目录中。
我们可以对文件执行的三个操作如下 -
打开一个文件。
处理文件(读、写、修改)。
保存并关闭文件。
以下是将偶数、奇数和质数存储到单独文件中的 C 程序-
#include <stdio.h> #include <stdlib.h> /* Function declarations */ int even(const int num); int prime(const int num); int main(){ FILE * fptrinput, * fptreven, * fptrodd, * fptrprime; int num, success; fptrinput = fopen("numbers.txt", "r"); fptreven = fopen("even-numbers.txt" , "w"); fptrodd = fopen("odd-numbers.txt" , "w"); fptrprime= fopen("prime-numbers.txt", "w"); if(fptrinput == NULL || fptreven == NULL || fptrodd == NULL || fptrprime == NULL){ /* Unable to open file hence exit */ printf("Unable to open file.\n"); exit(EXIT_FAILURE); } /* File open success message */ printf("File opened successfully. Reading integers from file. \n\n"); // 读取一个整数并成功存储读取状态。 while (fscanf(fptrinput, "%d", &num) != -1){ if (prime(num)) fprintf(fptrprime, "%d\n", num); else if (even(num)) fprintf(fptreven, "%d\n", num); else fprintf(fptrodd, "%d\n", num); } fclose(fptrinput); fclose(fptreven); fclose(fptrodd); fclose(fptrprime); printf("数据写入成功。"); return 0; } int even(const int num){ return !(num & 1); } int prime(const int num){ int i; if (num < 0) return 0; for ( i=2; i<=num/2; i++ ) { if (num % i == 0) { return 0; } } return 1; }输出结果
执行上述程序时,会产生以下结果 -
File opened successfully. Reading integers from file. 数据写入成功。
下面给出了用于将偶数、奇数和质数存储到单独文件中的程序的解释 -
Input file: numbers.txt file contains: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Which is open in read mode (already exists file) Separated even, odd and prime numbers in separate file after execution even-numbers.txt contains: 4 6 8 10 12 14 16 odd-numbers.txt contains: 9 15 prime-numbers.txt contains: 1 2 3 5 7 11 13 17