c - 使用 C 编辑文件

Question

输入.txt:

File entry structures:
[0] ""  0       -1
[1] ""  0       -1
[2] ""  0       -1
[3] ""  0       -1
[4] ""  0       -1

我想创建一个新文件 (output.txt)。 C 程序将第一次出现的“”替换为“Testfile”，因此它看起来像:

输出.txt:

File entry structures:
[0] "Testfile"  0       -1
[1] ""  0       -1
[2] ""  0       -1
[3] ""  0       -1
[4] ""  0       -1

我目前的工作:

#include <stdio.h>

int main() {
    FILE *input_file, *output_file;
    int  size, fblock;
    char index[81];
    char name[81];
    
    
    input_file = fopen("input.txt", "r");
    
    output_file = fopen("output.txt", "w");
    
    // ignore "File entry structures:" line when reading/writing
    
    while (fscanf(input_file, "%80s %80s %d %d", index, name, &size, &fblock) == 4) {
        fprintf(output_file, ... );
    }
    

    

我不知道要为 fprintf 的第二个参数提供什么。我的目标是以与输入文件中相同的方式编写它。

Answer 1

你太辛苦了。我太拖延了。这可以通过一个非常简单的状态机来完成:

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

FILE * xfopen(const char *path, const char *mode);

int
main(int argc, char **argv)
{
    int c;
    int seen = 0;
    FILE *in = argc > 1 ? xfopen(argv[1], "r") : stdin;
    FILE *out = argc > 2 ? xfopen(argv[2], "r") : stdout;

    while( (c = fgetc(in)) != EOF ){
        if( seen == 0 && c == '"' ){
            int d = fgetc(in);
            if( d == '"' ){
                fputs("\"Testfile", out);
                seen = 1;
            } else {
                ungetc(d, in);
            }
        }
        fputc(c, out);
    }
    return 0;
}

FILE *
xfopen(const char *path, const char *mode)
{
    FILE *fp = path[0] != '-' || path[1] != '\0' ? fopen(path, mode) :
        *mode == 'r' ? stdin : stdout;
    if( fp == NULL ){
        perror(path);
        exit(EXIT_FAILURE);
    }
    return fp;
}