c - 在 Linux 上用 C 打开文件时出现问题

标签 c linux buffer

我的 C 程序在 Windows 上运行良好，但在 Linux 上运行不佳。我使用以下方法逐行读取文件:

char * getLineOfAnySize(FILE* fp, size_t typicalSize, int *endOfLineDetected,size_t *nrOfCharRead){ 
char *line;       // buffer for our string
int ch;           // we will read line character by character
size_t len = 0;   // number of characters read (character counter)
size_t lineSize = typicalSize;  // initial size of the buffer allocated for the line
*nrOfCharRead = 0;

if(!fp) return NULL; // protection

// allocating the buffer
line = realloc(NULL, sizeof(char)*lineSize); // expected size of the line is pathHead to typicalSize

if (!line) return line; // protection, if we fail to allocate the memory we will return NULL

while (1) { // loop forever     
    ch = fgetc(fp);       // getting character by character from file

    if (ch == '\n') break; // end of line detected - breaking the loop 
    if( ch == EOF)  {
        *endOfLineDetected = 1;
        break; // end of file detected - breaking the loop
     }

    line[len++] = ch;     // store the character in the line buffer, increase character counter

    if (len == lineSize){ // we reached the end of line buffer (no more room)

        lineSize = lineSize + 64; // we have to increase the line size 
        line = realloc(line, sizeof(char)*(lineSize)); // line buffer has new size now

        if (!line) return line; // if we fail to allocate memory we will return NULL
    }
    if( (len == 0) && *endOfLineDetected){ // empty file
        *endOfLineDetected = 1;
        break; 
    } 
}


line[len++] ='\0';  // ending the string (notice there is no '\n' in the string)
*nrOfCharRead = len;

return line;       // return the string
}

我的程序的工作流程如下:我输入了一个路径，与该路径对应的文件在每一行中包含我用上面的函数读取并放入结构中的其他文件路径。在每个我应用 KMP 算法来获取字符串的出现。 当我尝试打开与我之前保存的路径相对应的文件时，我的程序出现了问题:

FILE *fp = NULL;
fp = fopen(list->path, "r"); 
    if(fp == NULL){
        fprintf(stderr, "Cannot open %s, exiting. . .\n", list->path);
        exit(1);
 }

屏幕上显示:

, exiting ...

由于文件打开问题，这太奇怪了，输出应该是:

Cannot open "list->path content", exiting. . .

尽管我不知道为什么在打开从输入文件读取的路径时会出现此错误。编译时没有问题。我正在考虑由函数“getLineOfAnySize 派生的缓冲区问题。我不是 Linux 用户，我只是试图运行该程序以确保它可以在两个操作系统上运行。不要不要考虑设计问题或逻辑问题，因为在 Windows 上一切正常。感谢所有愿意帮助我的人!如果需要，请询问有关代码的更多信息。

编辑:

输入文件的内容是:

/home/xxx/Scrivania/find/try
/home/xxx/Scrivania/find/try1

注意find是项目的目录

为了更好地理解变量和构造，以下是我的程序示例:

foo.c :

#include "foo.h"

FILE *fInput = NULL;  
FILE *fp = NULL;
char *line1; 
char *line2;
int endOfLineDetected = 0;
size_t nrOfCharRead = 0;
char ch;

fWord *w = NULL;
fWord *wordHead = NULL;
fWord *wordTail = NULL;

fList *list = NULL;
fList *listHead = NULL;
fList *listTail = NULL;

fPath *pathHead = NULL;
fPath *pathTail = NULL;

fPosition *positionHead = NULL;
fPosition *head = NULL;
fPosition *current = NULL;

char * getLineOfAnySize(FILE* fp, size_t typicalSize, int *endOfLineDetected,size_t *nrOfCharRead);

int main(int argc, char *argv[]){

fInput = fopen(argv[1], "r"); //the file that contains the path of the file in which search.

if(fInput == NULL){
    fprintf(stderr, "Cannot open %s, exiting. . .\n", argv[1]);
    exit(1);
}

while(!endOfLineDetected){ //read line by line the input file in order to save the path in a structure
    line1 = getLineOfAnySize(fInput,128,&endOfLineDetected,&nrOfCharRead);
    fList *node = malloc (sizeof(fList));
    node->path = line1;
    node->next = NULL;

    if(listHead == NULL){
        listHead = listTail = node;
    }else{
        listTail = listTail->next = node;
    }
}

list = listHead;

fclose(fInput);

do{
    fWord *app = malloc(sizeof(fWord));
    printf("Insert the word to search: ");
    scanf("%s", app->word);
    app->totalOccurences = 0;
    app->p = NULL;
    app->next = NULL;

    if(wordHead == NULL){
        wordTail = wordHead = app;
    }else{
        wordTail = wordTail->next = app;
    }
    printf("Do you want to insert another word? (Y/N): ");
    scanf(" %c", &ch);
}while(ch == 'y' || ch == 'Y');

w = wordHead;

while(w != NULL){
    while(list != NULL){
        w->p = malloc(sizeof(fPath));
        w->p->fileOccurrences = 0;
        w->p->path = list->path;
        w->p->position = NULL;
        w->p->next = NULL;

        if(pathHead == NULL){
            pathTail = pathHead = w->p;
        }else{
            pathTail = pathTail->next = w->p;
        }

        fp = fopen(w->p->path, "r"); 
        if(fp == NULL){
            fprintf(stderr, "Cannot open %s, exiting. . .\n", w->p->path);
            exit(1);
        }

        int countLine = 0;
        endOfLineDetected = 0;

        while(!endOfLineDetected){
            line2 = getLineOfAnySize(fp,128,&endOfLineDetected,&nrOfCharRead);
            int n = strlen(line2);
            int m = strlen(w->word);
            w->p->fileOccurrences = w->p->fileOccurrences + KMP(line2, w->word, n, m, countLine, w->p);
            countLine = countLine + 1;
        }   

        w->totalOccurences = w->totalOccurences + w->p->fileOccurrences;
        w->p->position = getHead(); 
        w->p = w->p->next;
        list = list->next;
        fclose(fp);
    }
    w->p = pathHead;
    list = listHead;
    w = w->next;
    pathHead = NULL;
}

w = wordHead;

while(w != NULL){
    printf("WORD %s \r\n", w->word);
    printf("TOTAL %d \r\n", w->totalOccurences);
    pathHead = w->p;
    while(w->p != NULL){
        printf("FILE %s \r\n", w->p->path);
        printf("OCCURENCES %d   \r\n", w->p->fileOccurrences);
        positionHead = w->p->position;
        while (w->p->position != NULL){
            printf("%d %d\r\n", w->p->position->line, w->p->position->character);
            w->p->position = w->p->position->next;
        }
        w->p->position = positionHead;
        w->p = w->p->next;
    }
    w->p = pathHead;
    w = w->next;
}

w = wordHead;

printf("\r\n");

freeMemory();
freeKMP();

return 0;
}

char * getLineOfAnySize(FILE* fp, size_t typicalSize, int 
*endOfLineDetected,size_t *nrOfCharRead){ 
char *line;       // buffer for our string
int ch;           // we will read line character by character
size_t len = 0;   // number of characters read (character counter)
size_t lineSize = typicalSize;  // initial size of the buffer allocated for the line
*nrOfCharRead = 0;

if(!fp) return NULL; // protection

// allocating the buffer
line = realloc(NULL, sizeof(char)*lineSize); // expected size of the line is pathHead to typicalSize

if (!line) return line; // protection, if we fail to allocate the memory we will return NULL

while (1) { // loop forever     
    ch = fgetc(fp);       // getting character by character from file

    if (ch == '\n') break; // end of line detected - breaking the loop 
    if( ch == EOF)  {
        *endOfLineDetected = 1;
        break; // end of file detected - breaking the loop
     }

    line[len++] = ch;     // store the character in the line buffer, increase character counter

    if (len == lineSize){ // we reached the end of line buffer (no more room)

        lineSize = lineSize + 64; // we have to increase the line size 
        line = realloc(line, sizeof(char)*(lineSize)); // line buffer has new size now

        if (!line) return line; // if we fail to allocate memory we will return NULL
    }
    if( (len == 0) && *endOfLineDetected){ // empty file
        *endOfLineDetected = 1;
        break; 
    } 
}


line[len++] ='\0';  // ending the string (notice there is no '\n' in the string)
*nrOfCharRead = len;

return line;       // return the string
}

// Function to implement KMP algorithm
int KMP(const char* X, const char* Y, int m, int n, int line, fPath *app){

int count = 0;

// next[i] stores the index of next best partial match
int next[n + 1];

for (int i = 0; i < n + 1; i++)
    next[i] = 0;

for (int i = 1; i < n; i++){
    int j = next[i + 1];

    while (j > 0 && Y[j] != Y[i])
        j = next[j];

    if (j > 0 || Y[j] == Y[i])
        next[i + 1] = j + 1;
}

for (int i = 0, j = 0; i < m; i++){
    if(X[i] == Y[j]){
        if (++j == n){
            count = count + 1; //conta le occorrenze della parola nella riga in input   
            fPosition *node = malloc (sizeof(fPosition));
            node->line = line;
            node->character = i - j + 1;
            node->next = NULL;

            if(head == NULL){
                current = head = node;
            }else{
                current = current->next = node;
            }

            app->position = current;

        }
    }
    else if (j > 0) {
        j = next[j];
        i--;    // since i will be incremented in next iteration
    }
}

return count;
}

fPosition * getHead(){ //rimette il puntatore alla testa della lista
fPosition *app = head;
head = NULL;
return app;
}

void freeKMP(){
free(head);
free(current);
}

void freeMemory(){

list = listHead;
fList *tempL = NULL;
while(list != NULL){
    tempL = list;
    list = list->next;
    free(tempL);
}

w = wordHead;
fWord *tempW = NULL;
fPath *tempP = NULL;
fPosition *tempO = NULL;
while(w != NULL){
    while(w->p != NULL){
        while(w->p->position != NULL){
            tempO = w->p->position;
            w->p->position = w->p->position->next;
            free(tempO);
        }
        tempP = w->p;
        w->p = w->p->next;
        free(tempP);
    }
    tempW = w;
    w = w->next;
    free(tempW);
}

free(w);
free(line1);
free(line2);
free(wordHead);
free(wordTail);
free(listHead);
free(listTail);
free(pathHead);
free(pathTail);
free(positionHead);
}

foo.h:

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

struct fileList{
char *path;
struct fileList *next;
};

struct filePath{
char *path;
int fileOccurrences;
struct OccurrencesPosition *position;
struct filePath *next;
 };

struct fileWord{
char word[50];
int totalOccurences;
struct filePath *p;
struct fileWord *next;
};

struct OccurrencesPosition{
int line;
int character;
struct OccurrencesPosition *next;    
};

typedef struct filePath fPath; 
typedef struct fileWord fWord;
typedef struct OccurrencesPosition fPosition;
typedef struct fileList fList;

fPosition * getHead();

int KMP(const char* X, const char* Y, int m, int n, int line, fPath *app);

void freeMemory();

void freeKMP();

也许我释放内存的方式也不正确。

最佳答案

这不是完整的答案，而是进一步分析的提示。

我用问题中显示的输入文件内容测试了程序，并输入了一两个单词。

如果第一个文件不存在，我会收到预期的错误消息:

Cannot open /home/yuripaoloni/Scrivania/find/try, exiting. . .

然后我修改了输入文件以列出我系统上存在的两个文件并得到一条错误消息

Cannot open , exiting. . .

我扩展了尝试打开文件以获得更多输出的代码:

       fp = fopen(w->p->path, "r");
        if(fp == NULL){
            fprintf(stderr, "Cannot open %s, exiting. . .\n", w->p->path);
            perror("fopen");
            exit(1);
        } else {
            printf("Successfully opened %s\n", w->p->path);
        }

这打印

$ ./foo input                                        
Insert the word to search: foo
Do you want to insert another word? (Y/N): y
Insert the word to search: bar
Do you want to insert another word? (Y/N): y
Insert the word to search: baz
Do you want to insert another word? (Y/N): n
Successfully opened /home/username/tmp/try
Successfully opened /home/username/tmp/try1
Cannot open , exiting. . .
fopen: No such file or directory

显然您的程序试图打开现有文件名之后的第三个文件。 w->p->path 可能是 NULL 指针或可能指向空字符串。

当我只输入一个单词时出现同样的错误。我没有进一步分析错误。

要找出您的程序为何尝试打开一个空名称的文件，您可以在调试器中运行它或添加更多输出以查看在处理列表时执行了多少循环周期以及您找到了哪些数据。

关于c - 在 Linux 上用 C 打开文件时出现问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/58859401/

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