该程序从用户读取“ n”行并将其写入C中的文本文件

Question

I was asked to write a program that asks an integer from the user which represents that number of sentences that the user will write to the text file. Then the user will write those sentences. My problem with the my code below is that it only reads the first sentence that i;ve input and it will be written to the text file. what's wrong with it? NOTE: the getline() won't work for some reason.keep on saying that "it was not declared on this scope". I'm using DEV-C btw.

main(){

    int n;
    char line[100];
    FILE *in_file;

    scanf("%d",&n);

    in_file = fopen("lines.txt","w");

    for(int i=0;i<n;i++){
        gets(line);
        fprintf(in_file,"%s",line); 
    }

    fclose(in_file);

    system("pause");
}

Answer 1

1) Instead of gets() you should always use fgets() .

If you compile the code with gets() you'll get the following warning on GCC:

/tmp/ccq8G5WV.o: In function `main':

writelines.c:(.text+0x62): warning: the `gets' function is dangerous and should not be used.

2) After you enter number of lines to write in lines.txt ie scanf("%d",&n); you need to remove \\n from the input stream.

Try this example:

---

#include<stdio.h>
int main()
{

    int n, i, c;
    char line[100];
    FILE *in_file;

    scanf("%d",&n);
    //Remove \n from input stream
    while ( (c = getchar()) != '\n' && c != EOF );

    in_file = fopen("lines.txt","w");

    for(i=0; i<n; i++)
    {
        fgets(line, 100, stdin);
        fprintf(in_file,"%s",line); 
    }

    fclose(in_file);

    return 0;
}

Answer 2

The above answer is very ok. scanf just read the characters before \\n and leave out the \\n in the stream buffer. You should remove it, otherwise it will count as one line. Besides, fprintf should add \\n for very line because gets() also remove \\n from your input. If not, all lines will concantenate together and display one line. I just combine the above answer and you original code.

#include <stdio.h>
int main(){

    int n;
    int i;
    char c;
    char line[100];
    FILE *in_file;

    scanf("%d",&n);
    while ( (c = getchar()) != '\n' && c != EOF )
        ;

    in_file = fopen("lines.txt","w");

    for(i=0;i<n;i++){
        gets(line);
        fprintf(in_file,"%s\n",line); 
    }   

    fclose(in_file);
}