C：EOF检测和测试；fgetc

目标： 如何成功实现EOF以停止无限循环

调用函数的部分：

do {
    pId = readInputField(fptr, DELIMITER_SPACE);
    pName = readInputField(fptr, DELIMITER_SEMICOLON);
    pDob = readInputField(fptr, DELIMITER_SPACE);
    pHobbyList = readInputField(fptr, DELIMITER_NEWLINE);
} while (NULL != pId
         && NULL != pName
         && NULL != pDob
         && NULL != pHobbyList);

char* readInputField(FILE* fPtr, const char delimiter) {
    int numCharRead;
    char bufferString[MAX_LENGTH_INPUT];
    char *pBufferString;

    numCharRead = 0;

    // flush: if spaces are found
    ' ' == (bufferString[numCharRead] = fgetc(fPtr)) ? 0 : numCharRead++;

    // get chracter array before delimiter
    while (delimiter != bufferString[numCharRead - 1]
            && numCharRead < MAX_LENGTH_INPUT) {
        bufferString[numCharRead++] = fgetc(fPtr);
    }

    // exclude delimiter from the string
    bufferString[numCharRead - 1] = '\0';

    printf("numCharRead=  \"%d\"\n", numCharRead);

    printf("delimiter:    \"%c\"\n", delimiter);
    printf("bufferString: \"%s\"\n", bufferString);

    pBufferString = malloc(sizeof(char*) * strlen(bufferString));

    /* deleted:
    pBufferString = bufferString;
    return EOF == bufferString[numCharRead - 1] ? NULL : pBufferString;
    */
}

VIC Lee, Victoria; 02/25/90 Knitting;Photography;Dance;

numCharRead=  "4"
delimiter:    " "
bufferString: "VIC"
numCharRead=  "14"
delimiter:    ";"
bufferString: "Lee, Victoria"
numCharRead=  "9"
delimiter:    " "
bufferString: "02/25/90"
numCharRead=  "28"
delimiter:    "
"
bufferString: "Knitting;Photography;Dance;"

// after this, infinite loop begins with garbage data

函数定义：

do {
    pId = readInputField(fptr, DELIMITER_SPACE);
    pName = readInputField(fptr, DELIMITER_SEMICOLON);
    pDob = readInputField(fptr, DELIMITER_SPACE);
    pHobbyList = readInputField(fptr, DELIMITER_NEWLINE);
} while (NULL != pId
         && NULL != pName
         && NULL != pDob
         && NULL != pHobbyList);

char* readInputField(FILE* fPtr, const char delimiter) {
    int numCharRead;
    char bufferString[MAX_LENGTH_INPUT];
    char *pBufferString;

    numCharRead = 0;

    // flush: if spaces are found
    ' ' == (bufferString[numCharRead] = fgetc(fPtr)) ? 0 : numCharRead++;

    // get chracter array before delimiter
    while (delimiter != bufferString[numCharRead - 1]
            && numCharRead < MAX_LENGTH_INPUT) {
        bufferString[numCharRead++] = fgetc(fPtr);
    }

    // exclude delimiter from the string
    bufferString[numCharRead - 1] = '\0';

    printf("numCharRead=  \"%d\"\n", numCharRead);

    printf("delimiter:    \"%c\"\n", delimiter);
    printf("bufferString: \"%s\"\n", bufferString);

    pBufferString = malloc(sizeof(char*) * strlen(bufferString));

    /* deleted:
    pBufferString = bufferString;
    return EOF == bufferString[numCharRead - 1] ? NULL : pBufferString;
    */
}

VIC Lee, Victoria; 02/25/90 Knitting;Photography;Dance;

numCharRead=  "4"
delimiter:    " "
bufferString: "VIC"
numCharRead=  "14"
delimiter:    ";"
bufferString: "Lee, Victoria"
numCharRead=  "9"
delimiter:    " "
bufferString: "02/25/90"
numCharRead=  "28"
delimiter:    "
"
bufferString: "Knitting;Photography;Dance;"

// after this, infinite loop begins with garbage data

样本输出：

do {
    pId = readInputField(fptr, DELIMITER_SPACE);
    pName = readInputField(fptr, DELIMITER_SEMICOLON);
    pDob = readInputField(fptr, DELIMITER_SPACE);
    pHobbyList = readInputField(fptr, DELIMITER_NEWLINE);
} while (NULL != pId
         && NULL != pName
         && NULL != pDob
         && NULL != pHobbyList);

char* readInputField(FILE* fPtr, const char delimiter) {
    int numCharRead;
    char bufferString[MAX_LENGTH_INPUT];
    char *pBufferString;

    numCharRead = 0;

    // flush: if spaces are found
    ' ' == (bufferString[numCharRead] = fgetc(fPtr)) ? 0 : numCharRead++;

    // get chracter array before delimiter
    while (delimiter != bufferString[numCharRead - 1]
            && numCharRead < MAX_LENGTH_INPUT) {
        bufferString[numCharRead++] = fgetc(fPtr);
    }

    // exclude delimiter from the string
    bufferString[numCharRead - 1] = '\0';

    printf("numCharRead=  \"%d\"\n", numCharRead);

    printf("delimiter:    \"%c\"\n", delimiter);
    printf("bufferString: \"%s\"\n", bufferString);

    pBufferString = malloc(sizeof(char*) * strlen(bufferString));

    /* deleted:
    pBufferString = bufferString;
    return EOF == bufferString[numCharRead - 1] ? NULL : pBufferString;
    */
}

VIC Lee, Victoria; 02/25/90 Knitting;Photography;Dance;

numCharRead=  "4"
delimiter:    " "
bufferString: "VIC"
numCharRead=  "14"
delimiter:    ";"
bufferString: "Lee, Victoria"
numCharRead=  "9"
delimiter:    " "
bufferString: "02/25/90"
numCharRead=  "28"
delimiter:    "
"
bufferString: "Knitting;Photography;Dance;"

// after this, infinite loop begins with garbage data

我想看看上面的返回语句。出于某种原因，它无法检测是否为EOF

感谢您的帮助！谢谢

---

更新： 谢谢@JoachimPileborg！我已更新了以下代码：

  // check for EOF
    if(bufferString[numCharRead-1] == EOF) {
        return NULL;
    } else {
        pBufferString = malloc(sizeof(char*));
        strcpy(pBufferString, bufferString);
        return pBufferString;
    }

---

检查从文件中读取的

EOF

，如下所示

// flush: if spaces are found
' ' == (bufferString[numCharRead] = fgetc(fPtr)) ? 0 : numCharRead++;
if(bufferString[numCharRead-1] == EOF)
    return NULL;

while (delimiter != bufferString[numCharRead - 1]
            && numCharRead < MAX_LENGTH_INPUT) {
    bufferString[numCharRead++] = fgetc(fPtr);
    /* check for EOF */
    if(bufferString[numCharRead-1] == EOF)
        return NULL;
}

//刷新：如果找到空格
''==（缓冲字符串[numCharRead]=fgetc（fPtr））？0:numCharRead++；
if（缓冲字符串[numCharRead-1]==EOF）
返回NULL；
while（分隔符！=bufferString[numCharRead-1]
&&numCharRead<最大长度\输入）{
bufferString[numCharRead++]=fgetc（fPtr）；
/*检查EOF*/
if（缓冲字符串[numCharRead-1]==EOF）
返回NULL；
}

你也有@Joachim Pileborg评论中提到的问题

• fgetc

  返回

  int

  非

  char

• 您返回的是函数的本地

  bufferString

---

无法在注释中编写代码，因此我将此作为答案发布
您在问题中有（或至少有）此代码：

pBufferString = malloc(sizeof(char*) * strlen(bufferString));
pBufferString = bufferString;
return EOF == bufferString[numCharRead - 1] ? NULL : pBufferString;

在上面的第一行中，分配内存并使

pBufferString

指向该内存
然后，在第二行中，使

pBufferString

指向本地数组

bufferString

，这样就不再有指向分配给

malloc

的内存的指针，从而导致内存泄漏（以及稍后尝试

释放该指针时可能发生的崩溃）

然后返回
pBufferString
，它现在指向本地数组，导致未定义的行为，因为本地数组占用的堆栈内存在函数返回后不再有效

除了上述问题之外，您还可以根据需要分配四到八倍的内存。指针的大小是四个或八个字节（取决于您是在32位还是64位平台上），但是
char
只有一个字节。使用
strlen（bufferString）+1
作为分配的大小就足够了：

pBufferString = malloc(strlen(bufferString) + 1);

您需要
+1
，因为字符串长度中不包含字符串终止符。
请记住
fgetc
返回的是
int
而不是
char
。哦，您遇到了一个更糟糕的问题：返回一个指向局部变量的指针。@JoachimPileborg谢谢。我更新了上面的代码以修复指针问题。关于
fgetc
，我甚至没有收到任何警告，结果与预期一样。您建议如何替换
fgetc
？您分配的内存几乎是所需内存的四到八倍
sizeof（char*）
为4或8。分配
strlen（…）+1
字节就足够了。您应该使用
strcpy
来复制字符串，现在您将指针更改为指向局部变量（因此仍然返回指向局部变量的指针）。
''==（bufferString[numCharRead]=fgetc（fPtr））？0:numCharRead++。。。这是一种非常复杂的表达
if（（bufferString[numCharRead]=fgetc（fPtr）））numCharRead++。非常感谢Rohan！无限循环发生在刷新中。我修改了代码；它没有停止无限循环！现在，情况更清楚了。我感谢你的意见！您将如何替换上述代码中的
fgetc
？
fgetc
返回
int
，而不是
char
，这有什么意义？@JaneBerman从技术上讲
255
是一个有效字符。不幸的是，如果使用
char
，它也可以被视为-1-对于
char
而言，1与对于
int
而言-1不同。