变量类型的系统wget

Question

所以，我有几个 url 存储在一个名为 url 的字符指针数组中，

我想在每个 url 上调用 wget，但我不断收到以下错误。

invalid operands to binary + (have 'char *' and 'char *')

我的程序是C语言的

system("wget" + url[0]);

Answer 1

在 C 中，+ 运算符不适用于字符串。要连接两个字符串并将结果传递给 system()，您可以执行以下操作：

char buffer[ENOUGH_SPACE_TO_HOLD_CONCATENATED_RESULT];  /* Destination buffer for our command */
snprintf(buffer, sizeof(buffer), "wget %s", url[0]);    /* You can also use strcat and friends for this step */
system(buffer);                                         /* Now execute it */

Answer 2

在 C 中，不能使用 + 运算符连接两个字符串。使用 strncat 代替：

NAME
       strcat, strncat - concatenate two strings

SYNOPSIS
       #include <string.h>

       char *strcat(char *dest, const char *src);

       char *strncat(char *dest, const char *src, size_t n);

DESCRIPTION
       The  strcat() function appends the src string to the dest string, over‐
       writing the null byte ('\0') at the end of dest, and then adds a termi‐
       nating  null  byte.   The  strings may not overlap, and the dest string
       must have enough space for the result.

       The strncat() function is similar, except that

       *  it will use at most n characters from src; and

       *  src does not need to be null-terminated if it  contains  n  or  more
          characters.

       As  with  strcat(),  the resulting string in dest is always null-termi‐
       nated.

       If src contains n or more characters, strncat() writes  n+1  characters
       to  dest  (n  from src plus the terminating null byte).  Therefore, the
       size of dest must be at least strlen(dest)+n+1.

谷歌搜索“strncat”将为您提供大量有关如何使用它的示例。