Linux and UNIX Man Pages

Test Your Knowledge in Computers #492
Difficulty: Medium
Transpilers are source-to-source compilers that directly produce assembly or machine code,
True or False?
Linux & Unix Commands - Search Man Pages

strncpy(3) [osx man page]

STRCPY(3)						   BSD Library Functions Manual 						 STRCPY(3)

NAME
stpcpy, strcpy, strncpy -- copy strings LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <string.h> char * stpcpy(char *s1, const char *s2); char * strcpy(char *restrict s1, const char *restrict s2); char * strncpy(char *restrict s1, const char *restrict s2, size_t n); DESCRIPTION
The stpcpy() and strcpy() functions copy the string s2 to s1 (including the terminating '' character). The strncpy() function copies at most n characters from s2 into s1. If s2 is less than n characters long, the remainder of s1 is filled with '' characters. Otherwise, s1 is not terminated. The source and destination strings should not overlap, as the behavior is undefined. RETURN VALUES
The strcpy() and strncpy() functions return s1. The stpcpy() function returns a pointer to the terminating '' character of s1. EXAMPLES
The following sets chararray to ``abc'': char chararray[6]; (void)strncpy(chararray, "abc", sizeof(chararray)); The following sets chararray to ``abcdef'': char chararray[6]; (void)strncpy(chararray, "abcdefgh", sizeof(chararray)); Note that it does not NUL terminate chararray, because the length of the source string is greater than or equal to the length argument. The following copies as many characters from input to buf as will fit and NUL terminates the result. Because strncpy() does not guarantee to NUL terminate the string itself, this must be done explicitly. char buf[1024]; (void)strncpy(buf, input, sizeof(buf) - 1); buf[sizeof(buf) - 1] = ''; This could be better achieved using strlcpy(3), as shown in the following example: (void)strlcpy(buf, input, sizeof(buf)); Note that, because strlcpy(3) is not defined in any standards, it should only be used when portability is not a concern. SECURITY CONSIDERATIONS
The strcpy() function is easily misused in a manner which enables malicious users to arbitrarily change a running program's functionality through a buffer overflow attack. (See the FSA and EXAMPLES.) SEE ALSO
bcopy(3), memccpy(3), memcpy(3), memmove(3), strlcpy(3) STANDARDS
The strcpy() and strncpy() functions conform to ISO/IEC 9899:1990 (``ISO C90''). The stpcpy() function is an MS-DOS and GNUism. The stpcpy() function conforms to no standard. HISTORY
The stpcpy() function first appeared in FreeBSD 4.4, coming from 1998-vintage Linux. BSD
August 9, 2001 BSD

Check Out this Related Man Page

STRCPY(3)						   BSD Library Functions Manual 						 STRCPY(3)

NAME
stpcpy, stpncpy, strcpy, strncpy -- copy strings LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <string.h> char * stpcpy(char *dst, const char *src); char * stpncpy(char *restrict dst, const char *restrict src, size_t n); char * strcpy(char *restrict dst, const char *restrict src); char * strncpy(char *restrict dst, const char *restrict src, size_t n); DESCRIPTION
The stpcpy() and strcpy() functions copy the string src to dst (including the terminating '' character). The stpncpy() and strncpy() functions copy at most n characters from src into dst. If src is less than n characters long, the remainder of dst is filled with '' characters. Otherwise, dst is not terminated. The source and destination strings should not overlap, as the behavior is undefined. RETURN VALUES
The strcpy() and strncpy() functions return dst. The stpcpy() and stpncpy() functions return a pointer to the terminating '' character of dst. If stpncpy() does not terminate dst with a NUL character, it instead returns a pointer to dst[n] (which does not necessarily refer to a valid memory location.) EXAMPLES
The following sets chararray to ``abc'': char chararray[6]; (void)strncpy(chararray, "abc", sizeof(chararray)); The following sets chararray to ``abcdef'': char chararray[6]; (void)strncpy(chararray, "abcdefgh", sizeof(chararray)); Note that it does not NUL terminate chararray, because the length of the source string is greater than or equal to the length argument. The following copies as many characters from input to buf as will fit and NUL terminates the result. Because strncpy() does not guarantee to NUL terminate the string itself, this must be done explicitly. char buf[1024]; (void)strncpy(buf, input, sizeof(buf) - 1); buf[sizeof(buf) - 1] = ''; This could be better achieved using strlcpy(3), as shown in the following example: (void)strlcpy(buf, input, sizeof(buf)); SECURITY CONSIDERATIONS
The strcpy(), strncpy(), stpcpy(), and stpncpy() functions are easily misused in a manner which enables malicious users to arbitrarily change a running program's functionality through a buffer overflow attack. (See the FSA and EXAMPLES.) It is recommended that strlcpy(3) be used instead as a way to avoid such problems. strlcpy(3) is not defined in any standards, but it has been adopted by most major libc implementations. SEE ALSO
bcopy(3), memccpy(3), memcpy(3), memmove(3), strlcpy(3), wcscpy(3) STANDARDS
The strcpy() and strncpy() functions conform to ISO/IEC 9899:1990 (``ISO C90''). The stpcpy() and stpncpy() functions conform to IEEE Std 1003.1-2008 (``POSIX.1''). HISTORY
The stpcpy() function first appeared in FreeBSD 4.4, and stpncpy() was added in FreeBSD 8.0. BSD
February 28, 2009 BSD

Featured Tech Videos