Ç - 与工作的fopen和fclose的fputc等 [英] C - Working with fopen, fclose, fputc etc

问题描述

我这有code终于在我的命令行一个参数工作，即一个文件为它一起工作，虽然我设计了$ C​​ $ c。与它的无限数量的工作理念的文件。它所做的是利用含有空格隔开的单词的文本文件的一些X数字，并用替换空间\\ n 从而创造一个单词列表。虽然，它成功完成了第一个参数，它只是忽略了第二位。

另一个小问题似乎还打印出在年底一些垃圾信件，A Y带两个点它上面;我认为一些EOF符号，但我似乎无法阻止这种情况发生！

  INT主（INT ARGC，字符** argv的）{
    FILE * fpIn，* fpOut;
    INT I，J;
    J = 1;
    焦炭℃;
    焦炭的myString [256];    的printf（％D的argc）;
    的printf（\\ n）;
    的printf（以下参数传递给main（））;
                对于（i = 1; I＆LT; ARGC，我++）的printf（％S的argv [I]）;
    的printf（\\ n）;    而（argc--）{
        对于（i = 1; I＆LT; ARGC，我++）{
            fpIn = FOPEN（的argv [J]，RB）;
            的snprintf（MyString的，256，％S〜[％D]。的argv [J]，I）;
            fpOut = FOPEN（MyString的，WB）;
            而（C！= EOF）{
                C =龟etc（fpIn）;
                如果（isspace为（c））的
                    C ='\\ n';
                的fputc（C，fpOut）;
            }
            J ++;
        }
    }
    返回0;
}
 

解决方案

的的getchar（）， GETC（）和龟etc（）函数（或宏）返回一个 INT ，而不是字符。

您必须使用：

  INT℃;而（（C =龟etc（fpIn））！= EOF）
{
    如果（isspace为（c））的
        C ='\\ n';
    的fputc（C，fpOut）;
}
 

想想吧;该功能必须能够返回任何有效的字符的和的EOF（这是任何有效截然不同字符价值，因此，根据定义，返回值不能是字符 ...

如果您使用会发生什么字符？

• 您原来的code没有初始化 C 之前对其进行测试（因此该循环可能会提早结束）。


• 您$​​ C $ C没有测试 C 阅读EOF后立即（所以它可能会打印垃圾字符，经常Y，拉丁小写字母Y带分音符，U + 00FF）。


• 如果你的字符类型是无符号的，你永远不会看到EOF。


• 如果你的字符类型有符号，一些有效的字符（经常再次Y））将作为PTED EOF misinter $ P $。

---

  

我似乎仍不能得到它的工作为多个参数虽然。

有你已经运行双回路问题：

  INT I，J;
J = 1;而（argc--）
{
    对于（i = 1; I＆LT; ARGC，我++）
    {
        fpIn = FOPEN（的argv [J]，RB）;
        ...过程fpIn ...
        J ++;
    }
}
 

让我们假设你调用与两个文件名的命令;那么的argc == 3 。

在第一时间过去，而循环，的argc == 2后。那么你做 A 为循环我取值1;打开的argv [1] （因为Ĵ== 1 ）。您处理的文件;然后增加Ĵ 2，之前也递增 I ，也为2周围的<$ C $第二次C>为循环， I == 2一样 ARGC ，所以为循环终止。该 2 while循环递减 ARGC 再次1，但测试！= 0 。但是，为环套 I = 1 ，然后终止，因为我== ARGC 。在，而循环递减 ARGC 1，并重复。

您可以使用，而环或为循环，但你并不需要两个。

所以，无论是：

 为（I = I; I＆LT; ARGC，我++）
{
    ...进程的argv [I] ...
}
 

或者

 而（--argc大于0）
{
    ...进程* argv的++ ...
}
 

我会使用为循环。

I've got this code finally working with a single argument on my command line, i.e. one file for it to work with, although I designed the code with the concept of it working with an unlimited number of files. What it does is take some X number of text files containing words separated by spaces, and replaces spaces with \n thus creating a list of words. Though, it successfully completes the first argument, it just ignores the 2nd.

Another minor problem seems that it also prints out some garbage letter at the end, a Y with two dots above it; I assume some EOF symbol, yet I can't seem to stop that happening!

int main(int argc, char** argv) {
    FILE *fpIn, *fpOut;
    int i, j;
    j = 1;
    char c;
    char myString[256];

    printf("%d", argc);
    printf("\n");
    printf("The following arguments were passed to main(): ");
                for(i=1; i<argc; i++) printf("%s ", argv[i]);
    printf("\n");

    while(argc--) {
        for(i = 1; i < argc; i++) {
            fpIn = fopen(argv[j], "rb");
            snprintf(myString, 256, "%s~[%d]", argv[j], i);
            fpOut= fopen(myString, "wb");
            while (c != EOF) {
                c = fgetc(fpIn);
                if (isspace(c)) 
                    c = '\n';
                fputc(c, fpOut );
            }
            j++;
        }
    }
    return 0;
}

解决方案

The getchar(), getc() and fgetc() functions (or macros) return an int, not a char.

You must use:

int c;

while ((c = fgetc(fpIn)) != EOF)
{
    if (isspace(c))
        c = '\n';
    fputc(c, fpOut);
}

Think about it; the functions must be able to return any valid char and EOF (which is distinct from any valid char value. So, by definition, the return value can't be a char...

What happens if you use char?

• Your original code didn't initialize c before testing it (so the loop might break early).
• Your code didn't test c immediately after reading EOF (so it might print a garbage character, often ÿ, LATIN SMALL LETTER Y WITH DIAERESIS, U+00FF).
• If your char type is unsigned, you'd never see EOF.
• If your char type is signed, some valid characters (often ÿ again)) will be misinterpreted as EOF.

---

I still can't seem to get it working for multiple arguments though.

The problem there is the double loop you have running:

int i, j;
j = 1;

while (argc--)
{
    for (i = 1; i < argc; i++)
    {
        fpIn = fopen(argv[j], "rb");
        ...process fpIn...
        j++;
    }
}

Let us suppose you invoke the command with two file names; then argc == 3.

After the first time past the while loop, argc == 2. You then do a for loop with i taking the value 1; you open argv[1] (because j == 1). You process that file; then increment j to 2, before also incrementing i, also to 2. The second time around the for loop, i == 2 as does argc, so the for loop terminates. The while loop decrements argc again to 1, but tests that 2 != 0. However, the for loop sets i = 1 and then terminates because i == argc. The while loop decrements argc to 1, and repeats.

You can use a while loop or a for loop, but you don't need both.

So, either:

for (i = i; i < argc; i++)
{
    ...process argv[i]...
}

Or:

while (--argc > 0)
{
    ...process *++argv...
}

I'd use the for loop.

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