摘自man文档: The strncpy() function is similar, except that at most n bytes of src are copied. Warning: If there is no null byte among the first n bytes of src, the string placed in dest will not be null-terminated.
为了确保dest以' '结尾, 一般要写成:
dest[sizeof(dest) - 1] = ' ';
strncpy(dest, src, sizeof(dest) - 1);
snprintf()会确保以' '结尾, 不需要设置dest末尾的' ', 一般写成:
snprintf(dest, sizeof(dest), ...)
strlen(dest)的最大长度为sizeof(dest) - 1.
摘自man文档: The functions snprintf() and vsnprintf() do not write more than size bytes (including the terminating null byte (' ')). If the output was truncated due to this limit then the return value is the number of characters (excluding the terminating null byte) which would have been written to the final string if enough space had been available. Thus, a return value of size or more means that the output was truncated. (See also below under NOTES.)
例如:
char str[64] = { 0 };
snprintf(str, 3, "abc");
printf("%s
", str);
结果: ab
一直以来, 将snprintf像strncpy一样用了, 才发现不用那么费事...
还有strncat(), 不需要设置dest末尾的' ', 但需要n + 1的空间.
摘自man文档: 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.