使用 C 中的库编辑 txt 文件

Question

我在扫描现有文件时遇到问题。

挑战在于我有一个包含一些字符串的源文本文件。我必须在这个文件中扫描 "o'clock" 这个词，在我找到它的地方，我必须把 "o'clock" 之前的词放在方括号中。

我找到了一个查找触发器的函数，但我不明白我接下来需要做什么。如果您能解释一下如何替换读取字符串中的字符，我将不胜感激。

例如：我们有一个字符串：

"Let's go to the graveyard at night - at twelve o'clock!"

我需要将单词 twelve 替换为 [twelve]。

代码如下：

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

int main() {
    FILE * fp; //open exists file
    FILE * fn; //open empty file
    char c[1000]; // buffer
    char trigger[] = "o'clock"; // the word before which the characters should be added
    char name [] = "startFile.txt"; // name of source file
    char secondName[] = "newFile.txt"; // name of output file
    fp = fopen (name, "r"); // open only for reading
    if (fp == NULL) { // testing on exists
        printf ( "Error");
        getchar ();
        return 0;
    }
    fn = fopen(secondName, "w"); // open empty file for writing
    while (!feof(fp)) { // scanning all string in the source
        if(fgets(c,1000, fp) != NULL) { // reading charter from file
            fprintf(fn, c); // writing charter from buffer "c" to empty file
            if (strstr(c, trigger)) { // find triggered word
                // I tried compare string which has a trigger-word
            }
        }
    }

    fclose(fp); // closing file
    fclose(fn);
    return 0;
}

Answer 1

在您的代码中，您将该行复制到输出文件，然后查找触发词。但目标是找到触发器并编辑字符串，然后才将行写入输出文件。此外，为了编辑该行，您需要知道在哪里找到了触发器，因此您需要保存搜索的输出。

所以，而不是：

    fprintf(fn, c); // writing charter from buffer "c" to empty file
    if (strstr(c, trigger)) { // find triggered word
        // I tried compare string which has a trigger-word
    }

我们需要：

    char *p = strstr(c, trigger);
    if (p) {
        // I tried compare string which has a trigger-word
    }
    fputs(c, fn); // writing charter from buffer "c" to empty file

所以现在我们找到了触发器，我们需要向后搜索以找到结尾，然后找到它之前的单词的开头。当我们找到它们时，我们需要创建一个点并插入编辑内容：

    char *p = strstr(c, trigger);
    if (p) {
        // ok we found the trigger - now we need to search backwards
        // to find the end and then the start of the word before
        while (p>c && p[-1]==' ') p--; // find the end of the word
        memmove(p+1, p, c+999 - p); // make a space for the ]
        *p = ']';
        while (p>c && p[-1]!=' ') p--; // find the start of the word
        memmove(p+1, p, c+999 - p); // make a space for the [
        *p = '[';
    }
    fputs(c, fn); // writing charter from buffer "c" to empty file

在这里试试：https://www.onlinegdb.com/H18Tgy9xu

但是，如果字符串中有多个“o-clock”怎么办？像这样：

Let's go to the graveyard at twelve o'clock and have dinner at six o'clock beforehand!

在这种情况下，您需要循环直到找到所有这些：

这是最终代码：

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

int main() {
    FILE * fp; //open exists file
    FILE * fn; //open empty file
    char c[1000]; // buffer
    char trigger[] = "o'clock"; // the word before which the characters should be added
    char name [] = "startFile.txt"; // name of source file
    char secondName[] = "newFile.txt"; // name of output file
    fp = fopen (name, "r"); // open only for reading
    if (fp == NULL) { // testing on exists
        printf ( "Error");
        getchar ();
        return 0;
    }
    fn = fopen(secondName, "w"); // open empty file for writing
    if (fn == NULL) { // testing on create
        printf ( "Error");
        getchar ();
        return 0;
    }
    while (fgets(c, 1000, fp)) { // scanning all string in the source
        char *p = c; // we need to start searching at the beginning
        do {
            p = strstr(p+1, trigger); // find the next oclock after this one
            if (p) {
                // ok we found the trigger - now we need to search backwards
                // to find the end and then the start of the word before
                while (p>c && p[-1]==' ') p--; // find the end of the word
                memmove(p+1, p, c+999 - p); // make a space for the ]
                *p = ']';
                while (p>c && p[-1]!=' ') p--; // find the start of the word
                memmove(p+1, p, c+999 - p); // make a space for the [
                *p = '[';
                p = strstr(p, trigger); // find that same oclock again
                // (we couldn't save the location because memmove has changed where it is)
            }
        } while (p); // as long as we found one, search again
        fputs(c, fn); // writing charter from buffer "c" to empty file
    }
    fclose(fp); // closing file
    fclose(fn);
    return 0;
}

在这里试试：https://onlinegdb.com/SJMrP15ld

使用 C 中的库编辑 txt 文件

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