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NAME
strcpy, strncpy - copy a string
SYNOPSIS
#include <string.h>
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;
}
The strcpy() and strncpy() functions return a pointer to the destina‐
tion string dest.
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 (that is,
if the programmer was stupid or lazy, and failed to check the size
before copying) then anything might happen. Overflowing fixed length
strings is a favorite cracker technique.
bcopy(3), memccpy(3), memcpy(3), memmove(3), wcscpy(3), wcsncpy(3)