小***范

Plain Text code ? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 NAME strcpy, strncpy - copy a string SYNOPSIS #include char *strcpy(char *dest, const char *src); char *strncpy(char *dest, const char *src, size_t n); DESCRIPTION The strcpy() function copies the string pointed to by src, including the terminating null byte ('\0'), to the buffer pointed to by dest. The strings may not overlap, and the destination string dest must be large enough to receive the copy. 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. If the length of src is less than n, strncpy() pads the remainder of dest with null bytes. A simple implementation of strncpy() might be: char * strncpy(char *dest, const char *src, size_t n) { size_t i; for (i = 0; i < n && src[i] != '\0'; i++) dest[i] = src[i]; for ( ; i < n; i++) dest[i] = '\0'; return dest; } RETURN VALUE The strcpy() and strncpy() functions return a pointer to the destina‐ tion string dest. CONFORMING TO SVr4, 4.3BSD, C89, C99. NOTES Some programmers consider strncpy() to be inefficient and error prone. If the programmer knows (i.e., includes code to test!) that the size of dest is greater than the length of src, then strcpy() can be used. If there is no terminating null byte in the first n characters of src, strncpy() produces an unterminated string in dest. Programmers often prevent this mistake by forcing termination as follows: strncpy(buf, str, n); if (n > 0) buf[n - 1]= '\0'; BUGS If the destination string of a strcpy() is not large enough, then any‐ thing might happen. Overflowing fixed-length string buffers is a favorite cracker technique for taking complete control of the machine. Any time a program reads or copies data into a buffer, the program first needs to check that there's enough space. This may be unneces‐ sary if you can show that overflow is impossible, but be careful: pro‐ grams can get changed over time, in ways that may make the impossible possible.谁说没有返回值。。。。。。。。。 只是你没有用变量去接收而已，strcpy返回拷贝后的目标字符串。

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Plain Text code ? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 NAME strcpy, strncpy - copy a string SYNOPSIS #include char *strcpy(char *dest, const char *src); char *strncpy(char *dest, const char *src, size_t n); DESCRIPTION The strcpy() function copies the string pointed to by src, including the terminating null byte ('\0'), to the buffer pointed to by dest. The strings may not overlap, and the destination string dest must be large enough to receive the copy. 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. If the length of src is less than n, strncpy() pads the remainder of dest with null bytes. A simple implementation of strncpy() might be: char * strncpy(char *dest, const char *src, size_t n) { size_t i; for (i = 0; i < n && src[i] != '\0'; i++) dest[i] = src[i]; for ( ; i < n; i++) dest[i] = '\0'; return dest; } RETURN VALUE The strcpy() and strncpy() functions return a pointer to the destina‐ tion string dest. CONFORMING TO SVr4, 4.3BSD, C89, C99. NOTES Some programmers consider strncpy() to be inefficient and error prone. If the programmer knows (i.e., includes code to test!) that the size of dest is greater than the length of src, then strcpy() can be used. If there is no terminating null byte in the first n characters of src, strncpy() produces an unterminated string in dest. Programmers often prevent this mistake by forcing termination as follows: strncpy(buf, str, n); if (n > 0) buf[n - 1]= '\0'; BUGS If the destination string of a strcpy() is not large enough, then any‐ thing might happen. Overflowing fixed-length string buffers is a favorite cracker technique for taking complete control of the machine. Any time a program reads or copies data into a buffer, the program first needs to check that there's enough space. This may be unneces‐ sary if you can show that overflow is impossible, but be careful: pro‐ grams can get changed over time, in ways that may make the impossible possible.谁说没有返回值。。。。。。。。。 只是你没有用变量去接收而已，strcpy返回拷贝后的目标字符串。