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strcpy, strncpy - copy a string
char *strcpy(char *dest, const char *src);
char *strncpy(char *dest, const char *src, size_t n);
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:
strncpy(char *dest, const char *src, size_t n)
for (i = 0; i < n && src[i] != '\0'; i++)
dest[i] = src[i];
for ( ; i < n; i++)
dest[i] = '\0';
The strcpy() and strncpy() functions return a pointer to the
destination string dest.
SVr4, 4.3BSD, C89, C99.
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';
If the destination string of a strcpy() is not large enough, then
anything 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
unnecessary if you can show that overflow is impossible, but be
careful: programs can get changed over time, in ways that may make the
bcopy(3), memccpy(3), memcpy(3), memmove(3), stpcpy(3), stpncpy(3),
strdup(3), string(3), wcscpy(3), wcsncpy(3)
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