1.\" $OpenBSD: strdup.3,v 1.22 2015/12/01 01:32:48 mmcc Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)strdup.3 8.1 (Berkeley) 6/9/93 31.\" 32.Dd $Mdocdate: December 1 2015 $ 33.Dt STRDUP 3 34.Os 35.Sh NAME 36.Nm strdup , 37.Nm strndup 38.Nd save a copy of a string 39.Sh SYNOPSIS 40.In string.h 41.Ft char * 42.Fn strdup "const char *s" 43.Ft char * 44.Fn strndup "const char *s" "size_t maxlen" 45.Sh DESCRIPTION 46The 47.Fn strdup 48function allocates sufficient memory for a copy of the string 49.Fa s , 50does the copy, and returns a pointer to it. 51The pointer may subsequently be used as an argument to the function 52.Xr free 3 . 53.Pp 54The 55.Fn strndup 56function behaves similarly to 57.Nm strdup 58but only copies up to 59.Fa maxlen 60characters from 61.Fa s . 62The resulting string is always NUL-terminated. 63.Pp 64If the memory allocation fails, 65.Dv NULL 66is returned. 67.Sh EXAMPLES 68The following will point 69.Va p 70to an allocated area of memory containing the NUL-terminated string 71.Qq foobar : 72.Bd -literal -offset indent 73char *p; 74 75p = strdup("foobar"); 76if (p == NULL) 77 err(1, NULL); 78.Ed 79.Sh ERRORS 80The 81.Fn strdup 82and 83.Fn strndup 84functions may fail and set the external variable 85.Va errno 86for any of the errors specified for the library function 87.Xr malloc 3 . 88.Sh SEE ALSO 89.Xr free 3 , 90.Xr malloc 3 , 91.Xr strcpy 3 , 92.Xr strlcpy 3 , 93.Xr strlen 3 , 94.Xr wcsdup 3 95.Sh STANDARDS 96The 97.Fn strdup 98and 99.Fn strndup 100functions conform to 101.St -p1003.1-2008 . 102.Sh HISTORY 103A 104.Fn strdup 105macro was first used in the 106.Bx 4.1c 107debugger, 108.Sy dbx . 109It was rewritten as a C function for the 110.Bx 4.3 111.Xr inetd 8 112and first appeared in the C library of 113.Bx 4.3 Reno . 114The 115.Fn strndup 116function appeared in glibc 2.0, was reimplemented for 117.Nx 4.0 , 118and ported to 119.Ox 4.8 . 120