1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)strcpy.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd February 28, 2009 36.Dt STRCPY 3 37.Os 38.Sh NAME 39.Nm stpcpy, stpncpy, strcpy , strncpy 40.Nd copy strings 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In string.h 45.Ft char * 46.Fn stpcpy "char * restrict dst" "const char * restrict src" 47.Ft char * 48.Fn stpncpy "char * restrict dst" "const char * restrict src" "size_t len" 49.Ft char * 50.Fn strcpy "char * restrict dst" "const char * restrict src" 51.Ft char * 52.Fn strncpy "char * restrict dst" "const char * restrict src" "size_t len" 53.Sh DESCRIPTION 54The 55.Fn stpcpy 56and 57.Fn strcpy 58functions 59copy the string 60.Fa src 61to 62.Fa dst 63(including the terminating 64.Ql \e0 65character.) 66.Pp 67The 68.Fn stpncpy 69and 70.Fn strncpy 71functions copy at most 72.Fa len 73characters from 74.Fa src 75into 76.Fa dst . 77If 78.Fa src 79is less than 80.Fa len 81characters long, 82the remainder of 83.Fa dst 84is filled with 85.Ql \e0 86characters. 87Otherwise, 88.Fa dst 89is 90.Em not 91terminated. 92.Sh RETURN VALUES 93The 94.Fn strcpy 95and 96.Fn strncpy 97functions 98return 99.Fa dst . 100The 101.Fn stpcpy 102and 103.Fn stpncpy 104functions return a pointer to the terminating 105.Ql \e0 106character of 107.Fa dst . 108If 109.Fn stpncpy 110does not terminate 111.Fa dst 112with a 113.Dv NUL 114character, it instead returns a pointer to 115.Li dst[n] 116(which does not necessarily refer to a valid memory location.) 117.Sh EXAMPLES 118The following sets 119.Va chararray 120to 121.Dq Li abc\e0\e0\e0 : 122.Bd -literal -offset indent 123char chararray[6]; 124 125(void)strncpy(chararray, "abc", sizeof(chararray)); 126.Ed 127.Pp 128The following sets 129.Va chararray 130to 131.Dq Li abcdef : 132.Bd -literal -offset indent 133char chararray[6]; 134 135(void)strncpy(chararray, "abcdefgh", sizeof(chararray)); 136.Ed 137.Pp 138Note that it does 139.Em not 140.Tn NUL 141terminate 142.Va chararray 143because the length of the source string is greater than or equal 144to the length argument. 145.Pp 146The following copies as many characters from 147.Va input 148to 149.Va buf 150as will fit and 151.Tn NUL 152terminates the result. 153Because 154.Fn strncpy 155does 156.Em not 157guarantee to 158.Tn NUL 159terminate the string itself, this must be done explicitly. 160.Bd -literal -offset indent 161char buf[1024]; 162 163(void)strncpy(buf, input, sizeof(buf) - 1); 164buf[sizeof(buf) - 1] = '\e0'; 165.Ed 166.Pp 167This could be better achieved using 168.Xr strlcpy 3 , 169as shown in the following example: 170.Pp 171.Dl "(void)strlcpy(buf, input, sizeof(buf));" 172.Pp 173Note that because 174.Xr strlcpy 3 175is not defined in any standards, it should 176only be used when portability is not a concern. 177.Sh SECURITY CONSIDERATIONS 178The 179.Fn strcpy 180function is easily misused in a manner which enables malicious users 181to arbitrarily change a running program's functionality through a 182buffer overflow attack. 183(See 184the FSA 185and 186.Sx EXAMPLES . ) 187.Sh SEE ALSO 188.Xr bcopy 3 , 189.Xr memccpy 3 , 190.Xr memcpy 3 , 191.Xr memmove 3 , 192.Xr strlcpy 3 , 193.Xr wcscpy 3 194.Sh STANDARDS 195The 196.Fn strcpy 197and 198.Fn strncpy 199functions 200conform to 201.St -isoC . 202The 203.Fn stpcpy 204and 205.Fn stpncpy 206functions conform to 207.St -p1003.1-2008 . 208.Sh HISTORY 209The 210.Fn stpcpy 211function first appeared in 212.Fx 4.4 , 213and 214.Fn stpncpy 215was added in 216.Fx 8.0 . 217