fscanf 返回值 [英] fscanf return value

问题描述

fscanf 在读取文件中的数据时返回什么.例如，

What does fscanf return when it reads data in the file. For example,

int number1, number2, number3, number4, c;

c = fscanf (spFile, "%d", &number1);
//c will be 1 in this case.

c = fscanf (spFile, "%d %d %d %d", &number1, &number1, &number3, &number4);
//in this case, c will return 4.

我只想知道为什么它会根据参数的数量返回这样的值.

I just want to know why it returns such values depending on the number of arguments.

推荐答案

来自 手册页Xscanf 函数族:

成功完成后，这些函数将返回成功匹配并分配输入项；这个数字可以为零在早期匹配失败的情况下.如果输入之前结束第一次匹配失败或转换，应返回EOF.如果一个发生读取错误，设置流的错误指示符，EOF应返回，并且 errno 应设置为指出错误

Upon successful completion, these functions shall return the number of successfully matched and assigned input items; this number can be zero in the event of an early matching failure. If the input ends before the first matching failure or conversion, EOF shall be returned. If a read error occurs, the error indicator for the stream is set, EOF shall be returned, and errno shall be set to indicate the error

因此您对 fscanf 的第一次调用返回 1，因为一个输入项 (&number1) 与格式说明符 %d 成功匹配.您对 fscanf 的第二次调用返回 4，因为所有 4 个参数都匹配.

So your first call to fscanf returns 1 because one input item (&number1) was successfully matched with the format specifier %d. Your second call to fscanf returns 4 because all 4 arguments were matched.

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