198 lines
5.0 KiB
Groff
198 lines
5.0 KiB
Groff
.\" $NetBSD: strerror.3,v 1.17 2010/10/25 07:37:11 wiz Exp $
|
|
.\"
|
|
.\" 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. 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
|
|
.Dd October 24, 2010
|
|
.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"
|
|
.In errno.h
|
|
.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 language-dependent 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 nul 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.
|
|
Note that in most cases the
|
|
.Xr err 3
|
|
and
|
|
.Xr warn 3
|
|
family of functions is preferable to
|
|
.Fn perror ;
|
|
they are more flexible and also print the program name.
|
|
.Pp
|
|
If the error number is not recognized, these functions pass an error message
|
|
string containing
|
|
.Dq Li "Unknown error:\ "
|
|
followed by the error number in decimal.
|
|
To warn about this,
|
|
.Fn strerror
|
|
sets
|
|
.Dv errno
|
|
to
|
|
.Er EINVAL ,
|
|
and
|
|
.Fn strerror_r
|
|
returns
|
|
.Er EINVAL .
|
|
Error numbers recognized by this implementation fall in
|
|
the range 0 \*[Lt]
|
|
.Fa errnum
|
|
\*[Lt]
|
|
.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 err 3 ,
|
|
.Xr psignal 3 ,
|
|
.Xr warn 3
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn perror
|
|
and
|
|
.Fn strerror
|
|
functions conform to
|
|
.St -isoC-99 .
|
|
The
|
|
.Fn strerror_r
|
|
function conforms 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 first appeared in
|
|
.Nx 4.0 .
|
|
.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 return type for
|
|
.Fn strerror
|
|
is missing a type-qualifier; it should actually be
|
|
.Vt const char * .
|
|
.Pp
|
|
Programs that use the deprecated
|
|
.Va sys_errlist
|
|
variable often fail to compile because they declare it
|
|
inconsistently.
|