edafcb6d73
Also add a note to the Bugs section pointing out that strerror() and perror() share the same static buffer.
192 lines
5.0 KiB
Groff
192 lines
5.0 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to Berkeley by
|
|
.\" the American National Standards Committee X3, on Information
|
|
.\" Processing Systems.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)strerror.3 8.1 (Berkeley) 6/9/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd October 22, 2002
|
|
.Dt STRERROR 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm perror ,
|
|
.Nm strerror ,
|
|
.Nm strerror_r ,
|
|
.Nm sys_errlist ,
|
|
.Nm sys_nerr
|
|
.Nd system error messages
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In stdio.h
|
|
.Ft void
|
|
.Fn perror "const char *string"
|
|
.Vt extern const char * const sys_errlist[] ;
|
|
.Vt extern const int sys_nerr ;
|
|
.In string.h
|
|
.Ft "char *"
|
|
.Fn strerror "int errnum"
|
|
.Ft int
|
|
.Fn strerror_r "int errnum" "char *strerrbuf" "size_t buflen"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn strerror ,
|
|
.Fn strerror_r
|
|
and
|
|
.Fn perror
|
|
functions look up the error message string corresponding to an
|
|
error number.
|
|
.Pp
|
|
The
|
|
.Fn strerror
|
|
function accepts an error number argument
|
|
.Fa errnum
|
|
and returns a pointer to the corresponding
|
|
message string.
|
|
.Pp
|
|
The
|
|
.Fn strerror_r
|
|
function renders the same result into
|
|
.Fa strerrbuf
|
|
for a maximum of
|
|
.Fa buflen
|
|
characters and returns 0 upon success.
|
|
.Pp
|
|
The
|
|
.Fn perror
|
|
function finds the error message corresponding to the current
|
|
value of the global variable
|
|
.Va errno
|
|
.Pq Xr intro 2
|
|
and writes it, followed by a newline, to the
|
|
standard error file descriptor.
|
|
If the argument
|
|
.Fa string
|
|
is
|
|
.Pf non- Dv NULL
|
|
and does not point to the null character,
|
|
this string is prepended to the message
|
|
string and separated from it by
|
|
a colon and space
|
|
.Pq Dq Li ":\ " ;
|
|
otherwise, only the error message string is printed.
|
|
.Pp
|
|
If
|
|
.Fa errnum
|
|
is not a recognized error number,
|
|
.Fn strerror
|
|
returns an error message string containing
|
|
.Dq Li "Unknown error:\ "
|
|
followed by the error number in decimal, while
|
|
.Fn strerror_r
|
|
leaves
|
|
.Fa strerrbuf
|
|
unchanged and returns
|
|
.Er EINVAL .
|
|
Error numbers recognized by this implementation fall in
|
|
the range 0 \(<=
|
|
.Fa errnum
|
|
<
|
|
.Fa sys_nerr .
|
|
.Pp
|
|
If insufficient storage is provided in
|
|
.Fa strerrbuf
|
|
(as specified in
|
|
.Fa buflen )
|
|
to contain the error string,
|
|
.Fn strerror_r
|
|
returns
|
|
.Er ERANGE
|
|
and
|
|
.Fa strerrbuf
|
|
will contain an error message that has been truncated and
|
|
.Dv NUL
|
|
terminated to fit the length specified by
|
|
.Fa buflen .
|
|
.Pp
|
|
The message strings can be accessed directly using the external
|
|
array
|
|
.Va sys_errlist .
|
|
The external value
|
|
.Va sys_nerr
|
|
contains a count of the messages in
|
|
.Va sys_errlist .
|
|
The use of these variables is deprecated;
|
|
.Fn strerror
|
|
or
|
|
.Fn strerror_r
|
|
should be used instead.
|
|
.Sh SEE ALSO
|
|
.Xr intro 2 ,
|
|
.Xr psignal 3
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn perror ,
|
|
.Fn strerror
|
|
and
|
|
.Fn strerror_r
|
|
functions conform to
|
|
.St -p1003.1-2001 .
|
|
.Sh HISTORY
|
|
The
|
|
.Fn strerror
|
|
and
|
|
.Fn perror
|
|
functions first appeared in
|
|
.Bx 4.4 .
|
|
The
|
|
.Fn strerror_r
|
|
function was implemented in
|
|
.Fx 4.4
|
|
by
|
|
.An Wes Peters Aq wes@FreeBSD.org .
|
|
.Sh BUGS
|
|
For unknown error numbers, the
|
|
.Fn strerror
|
|
function will return its result in a static buffer which
|
|
may be overwritten by subsequent calls.
|
|
.Pp
|
|
The
|
|
.Fn perror
|
|
function is implemented in terms of
|
|
.Fn strerror ,
|
|
hence it uses the same static buffer.
|
|
This behaviour is forbidden by
|
|
.St -isoC-99 .
|
|
.Pp
|
|
Programs that use the deprecated
|
|
.Va sys_errlist
|
|
variable often fail to compile because they declare it
|
|
inconsistently.
|