C 读、写和操作文件

Question

我有一个包含团队详细信息的文件。我需要代码来读取文件，并将获胜百分比写入第二个文件。我还需要使用指示的搜索功能来搜索团队的具体信息。该代码未写入百分比文件。当菜单显示时，第一个文件的内容被打印，但代码甚至在进入搜索选项之前就退出了。我刚刚学习 C。我很想知道为什么它不适合我。

#include <stdio.h>

#define NUM_TEAMS 50
#define LEN_LINE 40
#define LEN_NAME 25

char Name[NUM_TEAMS][LEN_NAME] = { 0 },
    league[NUM_TEAMS][LEN_NAME],
    division[NUM_TEAMS][LEN_NAME], 
    line[LEN_LINE];

int wins[NUM_TEAMS] = { 0 }, 
    losses[NUM_TEAMS] = {0}, 
    ties[NUM_TEAMS] = {0}, 
    pWin[NUM_TEAMS] = {0};

int main (void) {

    //getting the file
    FILE *filePtr;
    filePtr = fopen ("NFLStandings_20171031.txt", "r");
    if (filePtr == NULL) {
        printf ("Error: File did not open");
    }

    //executing
    displayWelcome ();

    select (filePtr);

    fclose (filePtr);

    return 0;
}

void displayWelcome ()
{
    printf ("............WElCOME TO THE FOOTBALL ANALYSIS.............\n\n\n\n");
}

//read file
void readFile (FILE * filePtr)
{
    int index = 0, count;

    while (index < NUM_TEAMS && fgets (line, sizeof (line), filePtr) != NULL) {
        sscanf (line, "%s%s%s%i%i%i", Name[index], league[index],
                division[index], &wins[index], &losses[index], &ties[index]);
        printf ("%s team in %s league and  %s division has won [%i] "
                "losing [%i] and tied in [%i] times \n",
                Name[index], league[index], division[index], wins[index],
                losses[index], ties[index]);
        index++;
    }

}

//find by name
void searchName (char name[], FILE * filePtr)
{
    int index = 0;

    while (index < NUM_TEAMS && fgets (line, sizeof (line), filePtr) != NULL) {
        sscanf (line, "%s%s%s%i%i%i", Name[index], league[index],
                division[index], &wins[index], &losses[index], &ties[index]);
        if (Name[index] == name) {
            printf ("The following team has the name");
            printf ("%s team in %s league and  %s division has won [%i] "
                    "losing [%i] and tied in [%i] times \n",
                    Name[index], league[index], division[index], wins[index],
                    losses[index], ties[index]);
            index++;
        }
    }
    if (index == 0)
        printf ("Sorry! No teams Found with such name");
}

//find by league
void searchLeague (char league1[], FILE * filePtr)
{
    int index = 0;

    while (index < NUM_TEAMS && fgets (line, sizeof (line), filePtr) != NULL) {
        sscanf (line, "%s%s%s%i%i%i", Name[index], league[index],
                division[index], &wins[index], &losses[index], &ties[index]);
        if (league[index] == league1) {
            printf ("The League has the following teams");
            printf ("%s team in %s league and  %s division has won [%i] "
                    "losing [%i] and tied in [%i] times \n",
                    Name[index], league[index], division[index], wins[index],
                    losses[index], ties[index]);
            index++;
        }
    }
    if (index == 0)
        printf ("Sorry! No teams Found with such League  name");
}

//search by percentage win
void searchpWin (char pWin_[], FILE * filePtr)
{
    int index = 0;

    while (index < NUM_TEAMS && fgets (line, sizeof (line), filePtr) != NULL) {
        sscanf (line, "%s%s%s%i%i%i", Name[index], league[index],
                division[index], &wins[index], &losses[index], &ties[index],
                &pWin[index]);
        if (pWin[index] == pWin_) {
            printf ("The Teams with the Percentage Win are  the following ");
            printf ("%s team in %s league and  %s division has won [%i] "
                    "losing [%i] and tied in [%i] times \n",
                    Name[index], league[index], division[index], wins[index],
                    losses[index], ties[index]);
            index++;
        }
    }
    if (index == 0)
        printf ("Sorry! No teams Found with such Percentage Win");
}

void searchDivision (char division1[], FILE * filePtr)
{
    int index = 0;

    while (index < NUM_TEAMS && fgets (line, sizeof (line), filePtr) != NULL) {
        sscanf (line, "%s%s%s%i%i%i", Name[index], league[index],
                division[index], &wins[index], &losses[index], &ties[index]);
        if (division[index] == division1) {
            printf ("The Division has the following teams");
            printf ("%s team in %s league and  %s division has won [%i] "
                    "losing [%i] and tied in [%i] times \n",
                    Name[index], league[index], division[index], wins[index],
                    losses[index], ties[index]);
            index++;
        }
    }
    if (index == 0)
        printf ("Sorry! No teams Found with such Division name");
}

//selection user Menu
void select (FILE * filePtr)
{
    int selection1 = 0;
    int selection2 = 0;

    do {
        printf ("Select the options(by typing 1,2 or 3) below to proceed \n"
                " 1. Print The Teams \n 2. Search Team \n 3. Exit \n");
        selection1 = scanf ("%d", &selection1);

        //incorrect choice
        if (selection1 > 2) {
            printf ("Invalid option! Try again");

        }
        //reading file
        if (selection1 == 1) {
            readFile (filePtr);
        }
        //option 2 Search data
        if (selection1 == 2) {
            printf ("Search by :\n 1. Team Name \n 2. By league \n "
                    "3. By division \n 4. By percentage wins \n");
            selection2 = scanf ("%d", &selection2);
        }

        switch (selection2) {
            case 1:
                printf ("Team name : \n");
                char name[10];
                scanf ("%c", name);

                searchName (name, filePtr);
                break;

            case 2:
                printf ("League name : \n");
                char league[10];
                scanf ("%c", league);
                searchLeague (league, filePtr);
                break;
            case 3:
                printf ("Division name : \n");
                char division[10];
                scanf ("%c", division);
                searchDivision (division, filePtr);
                break;
            case 4:
                printf ("Percentage win : \n");
                char pWin[10];
                scanf ("%c", pWin);
                searchpWin (pWin, filePtr);

                break;
            default:
                printf ("Invalid option.Try again!\n\n");
                break;
        }
    } while (selection1 == 0 || selection1 > 3);
}

Answer 1

评论中已经提到，您应该始终将函数原型(prototype)放在 main() 函数之前，并且当文件未正确打开时，您应该返回一些错误代码(等-1)。

你的选择功能完全是一团糟。不要这样做来获取用户输入:

    selection1 = scanf ("%d", &selection1);

scanf 函数返回写入的字符总数，或负数。因此，您所做的就是将 scanf 的返回值分配给 Selection1。在您的情况“选择选项(通过输入 1,2 或 3)”中，无论您输入 1,2 还是 3，selection1 都将始终为 1，因为您写入了 1 个字符。你应该做的是:

    scanf ("%d", &selection1);

现在进入 switch 语句...

scanf ("%c", name);

后一个语句“%c”读取单个字符。但你不想要一个角色，对吧？您想要一个字符串，所以也许可以尝试这个:

scanf ("%s", name);

此外，除非 Selection1 为 2，否则 Selection2 的整个 switch 语句完全没有意义，所以也许只有在那时执行它才是一个好主意。

进入搜索功能:

if (Name[index] == name)

后者比较引用值，而不是实际值。因此，您可能想对 strcmp() 函数进行一些研究并在那里使用它。

您不妨考虑一下 select 函数中 do-while 循环中的退出条件。你说过“1.打印团队\n 2.搜索团队\n 3.退出\n”所以也许你应该在有人输入3后终止循环？

无论如何，我已经注意到了一些最关键的错误，并且通过更多的努力，您也许能够使您的代码工作，因为这不是一个有人会为您做这件事的地方，而是会给您提供帮助一些建议和提示。不过，我强烈建议您再次学习 C 编程语言的基础知识。当我作为初学者开始学习它时(大约两年前)，我发现 Herbert Schildt 的“Teach Yourself C”非常有帮助。您可能想尝试一下。