在 C 中复制数组并清除 char 数组中的垃圾

Question

我正在尝试将一个大字符串与一个像 "https://cdn.sstatic.net/stackexchange/img/logos/so/so-logo.png"只有 url 和 NULL 终止符 https://cdn.sstatic.net/stackexchange/img/logos/so/so-logo.png\0 的较小数组，但我得到了垃圾数组。

问题应该出在这里:

pos2 = 0;
while (found == 0)
{
    c = fgetc (fp); // get char from file
    link[pos2] = c;
    if (link[pos2-1] == 'g' && link[pos2] == '\"') // png and jpg files
    {
    found = 1;
    }
    ++pos2;
}
--pos2;
found = 0;
char link2[pos2];
for (j = 1; j < pos2; ++j)
{
    link2[j-1] = link[j];
}
link2[j] = '\0';
//sprintf(cmd, "wget -O /home/arturo/Dropbox/Digital_Renders/%d \'%s\'", ++num, link2);
//system(cmd);
printf("%s\n", link2);// checking
sleep(1);

代码如下:

#include <stdio.h>
#include <stdlib.h> // for using system calls
#include <unistd.h> // for sleep

int main ()
{
    char  body[] = "forum-post-body-content", notes[] = "p-comment-notes", img[] = "img src=", link[200], cmd[200]={0}, file[10];
    int c, pos = 0, pos2 = 0, fin = 0, i, j, num = 0, found = 0;
    FILE *fp;

    for (i = 1; i < 500; ++i)
    {
        sprintf(cmd,"wget -O page%d.txt 'http://www.mtgsalvation.com/forums/creativity/artwork/340782-official-digital-rendering-thread?page=%d'",i,i);
        system(cmd);
        sprintf(file, "page%d.txt", i);
        fp = fopen (file, "r");
        while ((c = fgetc(fp)) != EOF)
        {
            if (body[pos] == c)
            {
                if (pos == 22)
                {
                    pos = 0;
                    while (fin == 0)
                    {
                        c = fgetc (fp);
                        if (feof (fp))
                            break;
                        if (notes[pos] == c)
                        {
                            if (pos == 14)
                            {
                                fin = 1;
                                pos = -1;
                            }
                            ++pos;
                        }
                        else
                        {
                            if(pos > 0)
                                pos = 0;
                        }
                        if (img[pos2] == c)
                        {
                            if (pos2 == 7)
                            {
                                pos2 = 0;
                                while (found == 0)
                                {
                                    c = fgetc (fp); // get char from file
                                    link[pos2] = c;
                                    if (pos2 > 0)
                                    {
                                        if(link[pos2-1] == 'g' && link[pos2] == '\"')
                                        {
                                        found = 1;
                                        }
                                    }
                                    ++pos2;
                                }
                                --pos2;
                                found = 0;
                                char link2[pos2];
                                for (j = 1; j < pos2; ++j)
                                {
                                    link2[j - 1] = link[j];
                                }
                                link2[j - 1] = '\0';
                                //sprintf(cmd, "wget -O /home/arturo/Dropbox/Digital_Renders/%d \'%s\'", ++num, link2);
                                //system(cmd);
                                printf("%s\n", link2);// checking
                                sleep(1);
                                pos2 = -1;
                            }
                            ++pos2;
                        }
                        else
                        {
                            if(pos2 > 0)
                                pos2 = 0;
                        }
                    }
                fin = 0;
                }
                ++pos;
            }
            else
                pos = 0;
        }
        // closing file
        fclose (fp);
        if (remove (file))
        {
            fprintf(stderr, "Can't remove file\n");
        }
    }
}

Answer 1

鉴于声明:

char cmd[50];

这条线不好:

sprintf(cmd,"wget -O page%d.txt 'http://www.mtgsalvation.com/forums/creativity/artwork/340782-official-digital-rendering-thread?page=%d'",i,i);

您正试图将 120 多个字符打包到一个 50 字节的缓冲区中；这不会可靠地工作。