C：如果我们不知道长度，如何用 fgets() 填充表格？

Question

I'm trying to fill a table word by word with the method fgets(). I need to fill a table with words(max 25) that the user write step by step. The problem is that on my terminal if I do for exemple :

• ab (then press Enter)
• ac (then press Enter)
• ad (then press Enter)
• tu (then press Enter)
• (then press ctrl+d to stop)

The output is:

• tu
• tu
• tu
• tu

So basically it just copy the last word for each input I've entered

I've tried to replace "tab[length] = line;" with "strcpy(tab[length], line);" but when I do this I've got a "Segmentation fault (core dumped)"

#define NBRE_CHAR 256

int main(int argc, char const *argv[])
{   
    char* tab[25];
    int length =0;
    char line[NBRE_CHAR];
    while(fgets(line,NBRE_CHAR,stdin) != NULL){
        line[strlen(line)-1] = '\0'; // to delete \n
        tab[length] = line;
        length++;
    }
    for (int i = 0; i < length; i++)
    {
        printf("%s\n", tab[i] );
    }
}

Answer 1

char* tab[25]; is an array of 25 pointers to characters (strings).

With tab[length] = line; you asign the buffer line to the array. But that doesn't copy the string. As a result, all entries point to your single line buffer, which will have your last entered string.

What you may want is:

    char* tab[25];
    //...
        tab[length]= malloc(strlen(line)+1);
        strcpy(tab[length], line);

This allocates memory for each string and then copies the contents of your buffer to this memory.