Name
asprintf, vasprintf - print to allocated string
打印到分配的字符串
Synopsis
#include <stdio.h>
int asprintf(char **strp, const char *fmt, ...);
int vasprintf(char **strp, const char *fmt, va_list ap);
Description
The functions asprintf() and vasprintf() are analogs of sprintf(3) and vsprintf(3), except that they allocate a string large enough to hold the output including the terminating null byte, and return a pointer to it via the first argument. This pointer should be passed to free(3) to release the allocated storage when it is no longer needed.
函数asprintf（）和vasprintf（）是sprintf（3）和vsprintf（3）的类似函数，除了它们分配一个足够大的字符串来保存包括终止空字节的输出，并通过第一个参数返回指向它的指针。 应该将此指针传递给free（3）以在不再需要时释放已分配的存储。
Return Value
When successful, these functions return the number of bytes printed, just like sprintf(3). If memory allocation wasn’t possible, or some other error occurs, these functions will return -1, and the contents of strp is undefined.
成功时，这些函数返回打印的字节数，就像sprintf（3）一样。 如果无法进行内存分配或发生其他错误，则这些函数将返回-1，并且strp的内容未定义。
Conforming to
These functions are GNU extensions, not in C or POSIX. They are also available under *BSD. The FreeBSD implementation sets strp to NULL on error.
这些函数是GNU扩展，而不是C或POSIX。 它们也可以在* BSD下获得。 FreeBSD实现在出错时将strp设置为NULL。