This is a sample that will be written together in programming 2 in the class dedicated to structures.<\/p>\n
Data file format is\u00a0 <name> <grade><\/span> , where the name can consist from up to 63 characters and be a single word. Grade must be an integer. Data fields are separated by spaces.<\/p>\n Notice, that there is no guards for buffer overflow – if you enter 64 or more characters for the name, it will write beyond the bounds of the array and can cause data corruption or the program crashing.<\/strong><\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" This is a sample that will be written together in programming 2 in the class dedicated to structures. Data file format is\u00a0 <name> <grade> , where the name can consist from up to 63 characters and be a single word. Grade must be an integer. Data fields are separated by spaces. Notice, that there is … Loe edasi Reading from a file into structure array<\/span> \/**\r\n * File: struct_file.c\r\n * Author: Risto Heinsar\r\n * Created: 10.01.2021\r\n * Last edit: 22.06.2026\r\n *\r\n * Description: Reads student data from a file into a struct array.\r\n * Name of the file passed as first argument\r\n *\r\n * Compile using --std=c99 or later.\r\n *\/\r\n#include <stdio.h>\r\n#include <stdlib.h>\r\n\r\n\/* 1 to enable printing debug statements, 0 to silence them *\/\r\n#define DEBUG 1\r\n\r\n\/* Predefined array limits *\/\r\n#define STR_MAX_LEN 64\r\n#define STUDENT_MAX_CNT 32\r\n\r\n\/* Options for command line args *\/\r\n#define ARGS_CNT 2\r\n\r\n#define ARGS_EXEC_NAME 0\r\n#define ARGS_FILE_NAME 1\r\n\r\nstruct Student\r\n{\r\n char name[STR_MAX_LEN];\r\n int grade;\r\n};\r\n\r\nint ReadData(char *fName, struct Student *students, int limit);\r\nvoid PrintData(struct Student *students, int cnt);\r\n\r\nint main(int argc, char **argv)\r\n{\r\n \/* Check that argument was passed*\/\r\n if (argc != ARGS_CNT)\r\n {\r\n fprintf(stderr, \"Usage: %s data_file\\n\", argv[ARGS_EXEC_NAME]);\r\n return EXIT_FAILURE;\r\n }\r\n\r\n \/* Create struct array *\/\r\n struct Student studentGrades[STUDENT_MAX_CNT];\r\n\r\n \/* Read student data from file *\/\r\n int studentCnt = ReadData(argv[ARGS_FILE_NAME], studentGrades, STUDENT_MAX_CNT);\r\n\r\n \/* Print student data *\/\r\n PrintData(studentGrades, studentCnt);\r\n\r\n return EXIT_SUCCESS;\r\n}\r\n\r\n\/**\r\n * Description: Reads student data from a file into a struct array\r\n *\r\n * Parameters: fileName - name of the file for input data\r\n * students - struct array to store the data\r\n * limit - maximum entries to read (struct array size)\r\n *\r\n * Return: Number of studens read from the file\r\n *\/\r\nint ReadData(char *fileName, struct Student *students, int limit)\r\n{\r\n FILE *fStudents = fopen(fileName, \"r\");\r\n if (fStudents == NULL)\r\n {\r\n \/* Prints custom message + system error message from errno to stderr *\/\r\n perror(\"Error! Cannot open input file\");\r\n\r\n \/* Returns 0 students read from the file, allows program to continue *\/\r\n return 0;\r\n }\r\n\r\n if (DEBUG) printf(\"Opened '%s' for reading student data\\n\", fileName);\r\n\r\n \/* Counter for number of students from file *\/\r\n int cnt = 0;\r\n\r\n while (fscanf(fStudents, \"%s %d\", students[cnt].name,\r\n &students[cnt].grade) == 2)\r\n {\r\n \/* Debugging print to check if input was read successfully *\/\r\n if (DEBUG)\r\n printf(\"DBG: from file (%d): %s %d\\n\", cnt + 1,\r\n students[cnt].name,\r\n students[cnt].grade);\r\n\r\n \/* Student successfully read, increment student count *\/\r\n cnt++;\r\n\r\n \/* Avoid overflowing the array *\/\r\n if (cnt >= limit)\r\n {\r\n fprintf(stderr, \"Error! File is too long! Allowed max is %d!\\n\"\r\n \"Reading of the file has been stopped, continuing \"\r\n \"with a partial dataset!\\n\", limit);\r\n break;\r\n }\r\n }\r\n\r\n \/* Close the input file *\/\r\n fclose(fStudents);\r\n\r\n if (DEBUG) printf(\"DBG: Reading finished, got %d entries\\n\", cnt);\r\n\r\n \/* Returns number of students read *\/\r\n return cnt;\r\n}\r\n\r\n\/**\r\n * Description: Prints the Student array contents\r\n *\r\n * Parameters: students - student data\r\n * cnt - num of students in data array\r\n *\r\n * Return: none\r\n *\/\r\nvoid PrintData(struct Student *students, int cnt)\r\n{\r\n \/* Handling of no students *\/\r\n if (cnt <= 0)\r\n {\r\n fprintf(stderr, \"Error! Student db is empty!\\n\");\r\n return;\r\n }\r\n\r\n printf(\"Student list contains %d students:\\n\", cnt);\r\n for (int i = 0; i < cnt; i++)\r\n {\r\n printf(\"%s %d\\n\", students[i].name, students[i].grade);\r\n }\r\n}\r\n<\/pre>\n