kc3-lang/libbsd/man/strlcpy.3bsd

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  Date : 2023-02-20T00:11:10
  

  man: Update STANDARDS and HISTORY sections Include BSD versions when functions were introduced. Add mention whether these are BSD extensions.

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• man/strlcpy.3bsd

• .\" $OpenBSD: strlcpy.3,v 1.18 2005/08/06 03:24:19 jaredy Exp $
  .\"
  .\" Copyright (c) 1998, 2000 Todd C. Miller <Todd.Miller@courtesan.com>
  .\"
  .\" Permission to use, copy, modify, and distribute this software for any
  .\" purpose with or without fee is hereby granted, provided that the above
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  .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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  .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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  .Dd $Mdocdate: May 31 2007 $
  .Dt strlcpy 3bsd
  .Os
  .Sh NAME
  .Nm strlcpy ,
  .Nm strlcat
  .Nd size-bounded string copying and concatenation
  .Sh LIBRARY
  .ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
  .ds doc-str-Lb-libbsd \*[str-Lb-libbsd]
  .Lb libbsd
  .Sh SYNOPSIS
  .In string.h
  (See
  .Xr libbsd 7
  for include usage.)
  .Ft size_t
  .Fn strlcpy "char *dst" "const char *src" "size_t size"
  .Ft size_t
  .Fn strlcat "char *dst" "const char *src" "size_t size"
  .Sh DESCRIPTION
  The
  .Fn strlcpy
  and
  .Fn strlcat
  functions copy and concatenate strings respectively.
  They are designed
  to be safer, more consistent, and less error prone replacements for
  .Xr strncpy 3
  and
  .Xr strncat 3 .
  Unlike those functions,
  .Fn strlcpy
  and
  .Fn strlcat
  take the full size of the buffer (not just the length) and guarantee to
  NUL-terminate the result (as long as
  .Fa size
  is larger than 0 or, in the case of
  .Fn strlcat ,
  as long as there is at least one byte free in
  .Fa dst ) .
  Note that a byte for the NUL should be included in
  .Fa size .
  Also note that
  .Fn strlcpy
  and
  .Fn strlcat
  only operate on true
  .Dq C
  strings.
  This means that for
  .Fn strlcpy
  .Fa src
  must be NUL-terminated and for
  .Fn strlcat
  both
  .Fa src
  and
  .Fa dst
  must be NUL-terminated.
  .Pp
  The
  .Fn strlcpy
  function copies up to
  .Fa size
  - 1 characters from the NUL-terminated string
  .Fa src
  to
  .Fa dst ,
  NUL-terminating the result.
  .Pp
  The
  .Fn strlcat
  function appends the NUL-terminated string
  .Fa src
  to the end of
  .Fa dst .
  It will append at most
  .Fa size
  - strlen(dst) - 1 bytes, NUL-terminating the result.
  .Sh RETURN VALUES
  The
  .Fn strlcpy
  and
  .Fn strlcat
  functions return the total length of the string they tried to create.
  For
  .Fn strlcpy
  that means the length of
  .Fa src .
  For
  .Fn strlcat
  that means the initial length of
  .Fa dst
  plus
  the length of
  .Fa src .
  While this may seem somewhat confusing, it was done to make
  truncation detection simple.
  .Pp
  Note, however, that if
  .Fn strlcat
  traverses
  .Fa size
  characters without finding a NUL, the length of the string is considered
  to be
  .Fa size
  and the destination string will not be NUL-terminated (since there was
  no space for the NUL).
  This keeps
  .Fn strlcat
  from running off the end of a string.
  In practice this should not happen (as it means that either
  .Fa size
  is incorrect or that
  .Fa dst
  is not a proper
  .Dq C
  string).
  The check exists to prevent potential security problems in incorrect code.
  .Sh EXAMPLES
  The following code fragment illustrates the simple case:
  .Bd -literal -offset indent
  char *s, *p, buf[BUFSIZ];
  
  \&...
  
  (void)strlcpy(buf, s, sizeof(buf));
  (void)strlcat(buf, p, sizeof(buf));
  .Ed
  .Pp
  To detect truncation, perhaps while building a pathname, something
  like the following might be used:
  .Bd -literal -offset indent
  char *dir, *file, pname[MAXPATHLEN];
  
  \&...
  
  if (strlcpy(pname, dir, sizeof(pname)) >= sizeof(pname))
  	goto toolong;
  if (strlcat(pname, file, sizeof(pname)) >= sizeof(pname))
  	goto toolong;
  .Ed
  .Pp
  Since it is known how many characters were copied the first time, things
  can be sped up a bit by using a copy instead of an append:
  .Bd -literal -offset indent
  char *dir, *file, pname[MAXPATHLEN];
  size_t n;
  
  \&...
  
  n = strlcpy(pname, dir, sizeof(pname));
  if (n >= sizeof(pname))
  	goto toolong;
  if (strlcpy(pname + n, file, sizeof(pname) - n) >= sizeof(pname) - n)
  	goto toolong;
  .Ed
  .Pp
  However, one may question the validity of such optimizations, as they
  defeat the whole purpose of
  .Fn strlcpy
  and
  .Fn strlcat .
  As a matter of fact, the first version of this manual page got it wrong.
  .Sh SEE ALSO
  .Xr snprintf 3 ,
  .Xr strncat 3 ,
  .Xr strncpy 3
  .Sh HISTORY
  The
  .Fn strlcpy
  and
  .Fn strlcat
  functions first appeared in
  .Ox 2.4 ,
  and made their appearance in
  .Nx 1.4.3
  and
  .Fx 3.3 .
  

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