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2.\" The Regents of the University of California. All rights reserved.
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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.
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36.\" @(#)strcpy.3 8.1 (Berkeley) 6/4/93
37.\" $FreeBSD: src/lib/libc/string/strcpy.3,v 1.24 2002/12/19 09:40:24 ru Exp $
38.\"
39.Dd August 9, 2001
40.Dt STRCPY 3
41.Os
42.Sh NAME
43.Nm stpcpy ,
44.Nm strcpy ,
45.Nm strncpy
46.Nd copy strings
47.Sh LIBRARY
48.Lb libc
49.Sh SYNOPSIS
50.In string.h
51.Ft char *
52.Fo stpcpy
53.Fa "char *s1"
54.Fa "const char *s2"
55.Fc
56.Ft char *
57.Fo strcpy
58.Fa "char *restrict s1"
59.Fa "const char *restrict s2"
60.Fc
61.Ft char *
62.Fo strncpy
63.Fa "char *restrict s1"
64.Fa "const char *restrict s2"
65.Fa "size_t n"
66.Fc
67.Sh DESCRIPTION
68The
69.Fn stpcpy
70and
71.Fn strcpy
72functions
73copy the string
74.Fa s2
75to
76.Fa s1
77(including the terminating
78.Ql \e0
79character).
80.Pp
81The
82.Fn strncpy
83function copies at most
84.Fa n
85characters from
86.Fa s2
87into
88.Fa s1 .
89If
90.Fa s2
91is less than
92.Fa n
93characters long,
94the remainder of
95.Fa s1
96is filled with
97.Ql \e0
98characters.
99Otherwise,
100.Fa s1
101is
102.Em not
103terminated.
104.Sh RETURN VALUES
105The
106.Fn strcpy
107and
108.Fn strncpy
109functions
110return
111.Fa s1 .
112The
113.Fn stpcpy
114function returns a pointer to the terminating
115.Ql \e0
116character of
117.Fa s1 .
118.Sh EXAMPLES
119The following sets
120.Va chararray
121to
122.Dq Li abc\e0\e0\e0 :
123.Bd -literal -offset indent
124char chararray[6];
125
126(void)strncpy(chararray, "abc", sizeof(chararray));
127.Ed
128.Pp
129The following sets
130.Va chararray
131to
132.Dq Li abcdef :
133.Bd -literal -offset indent
134char chararray[6];
135
136(void)strncpy(chararray, "abcdefgh", sizeof(chararray));
137.Ed
138.Pp
139Note that it does
140.Em not
141.Tn NUL
142terminate
143.Va chararray ,
144because the length of the source string is greater than or equal
145to the length argument.
146.Pp
147The following copies as many characters from
148.Va input
149to
150.Va buf
151as will fit and
152.Tn NUL
153terminates the result.
154Because
155.Fn strncpy
156does
157.Em not
158guarantee to
159.Tn NUL
160terminate the string itself, this must be done explicitly.
161.Bd -literal -offset indent
162char buf[1024];
163
164(void)strncpy(buf, input, sizeof(buf) - 1);
165buf[sizeof(buf) - 1] = '\e0';
166.Ed
167.Pp
168This could be better achieved using
169.Xr strlcpy 3 ,
170as shown in the following example:
171.Pp
172.Dl "(void)strlcpy(buf, input, sizeof(buf));"
173.Pp
174Note that, because
175.Xr strlcpy 3
176is not defined in any standards, it should
177only be used when portability is not a concern.
178.Sh SECURITY CONSIDERATIONS
179The
180.Fn strcpy
181function is easily misused in a manner which enables malicious users
182to arbitrarily change a running program's functionality through a
183buffer overflow attack.
184(See
185the FSA
186and
187.Sx EXAMPLES . )
188.Sh SEE ALSO
189.Xr bcopy 3 ,
190.Xr memccpy 3 ,
191.Xr memcpy 3 ,
192.Xr memmove 3 ,
193.Xr strlcpy 3
194.Sh STANDARDS
195The
196.Fn strcpy
197and
198.Fn strncpy
199functions
200conform to
201.St -isoC .
202The
203.Fn stpcpy
204function is an MS-DOS and GNUism.
205The
206.Fn stpcpy
207function
208conforms to no standard.
209.Sh HISTORY
210The
211.Fn stpcpy
212function first appeared in
213.Fx 4.4 ,
214coming from 1998-vintage Linux.