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Man Pages


Manual Reference Pages  -  STRCPY (3)

NAME

stpcpy, stpncpy, strcpy, strncpy - copy strings

CONTENTS

Library
Synopsis
Description
Return Values
Examples
See Also
Standards
History
Security Considerations

LIBRARY


.Lb libc

SYNOPSIS


.In string.h char * stpcpy char * restrict dst const char * restrict src char * stpncpy char * restrict dst const char * restrict src size_t len char * strcpy char * restrict dst const char * restrict src char * strncpy char * restrict dst const char * restrict src size_t len

DESCRIPTION

The stpcpy and strcpy functions copy the string src to dst (including the terminating \0’ character.)

The stpncpy and strncpy functions copy at most len characters from src into dst. If src is less than len characters long, the remainder of dst is filled with \0’ characters. Otherwise, dst is not terminated.

RETURN VALUES

The strcpy and strncpy functions return dst. The stpcpy and stpncpy functions return a pointer to the terminating \0’ 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\0\0\0":
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] = ’\0’;

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.

SEE ALSO

bcopy(3), memccpy(3), memcpy(3), memmove(3), strlcpy(3), wcscpy(3)

STANDARDS

The strcpy and strncpy functions conform to -isoC. The stpcpy and stpncpy functions conform to -p1003.1-2008.

HISTORY

The stpcpy function first appeared in
.Fx 4.4 , and stpncpy was added in
.Fx 8.0 .

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.
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