在C ++中比较字符串

Question

I want to simplify a txt document and I tried this code:

#include <iostream>
#include <conio.h>

using namespace std;

int main()
{
    // 1. Step: Open files
    FILE *infile;
    FILE *outfile;
    char line[256];
    infile = fopen("vcard.txt", "r");
    outfile = fopen("records.txt", "w+");
    if(infile == NULL || outfile == NULL){
         cerr << "Unable to open files" << endl;
         exit(EXIT_FAILURE);
    }

    // 2.Step: Read from the infile and write to the outfile if the line is necessary
    /* Description:
    if the line is "BEGIN:VCARD" or "VERSION:2.1" or "END:VCARD" don't write it in the outfile
    */

    char word1[256] = "BEGIN:VCARD";
    char word2[256] = "VERSION:2.1";
    char word3[256] = "END:VCARD";

    while(!feof(infile)){
        fgets(line, 256, infile);
        if(strcmp(line,word1)!=0 && strcmp(line,word2)!=0 && strcmp(line,word3)!=0){ // If the line is not equal to these three words
          fprintf(outfile, "%s", line); // write that line to the file
        }
    }

    // 3.Step: Close Files
    fclose(infile);
    fclose(outfile);

    getch();
    return 0;
}

Unfortunately, despite the infile includes word1, word2 and word3 hundred times I still get 1 or -1 as the return value of strcmp.

What should I try?

Answer 1

fgets returns the newline character as part of the string. Since the strings you are comparing against don't contain a newline, they will be compared as different.

Since you are writing in C++, you may want to use std::ifstream and std::getline to read the file. The strings returned by getline will not have the newline in them, and as an added bonus you won't have to specify a limit on the line size.

Another (unrelated) issue: Using while (!foef(file)) is wrong, and can result in the last line being read twice. Instead, you should loop until fgets returns a null pointer.