.\" $OpenBSD: perror.3,v 1.2 1996/08/19 08:32:56 tholo Exp $ .\" .\" Copyright (c) 1980, 1991 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. .\" .Dd June 29, 1991 .Dt PERROR 3 .Os BSD 4 .Sh NAME .Nm perror .Nd write error messages to standard error .Sh SYNOPSIS .Fd #include <stdio.h> .Ft void .Fn perror "const char *string" .Sh DESCRIPTION The .Fn perror function looks up the language-dependent error message string affiliated with an error number and writes it, followed by a new-line, to the standard error stream. .Pp If the argument .Fa string is .Pf non- Dv NULL it is prepended to the message string and separated from it by a colon and a space .Pq Ql \&:\ \& . If .Fa string is .Dv NULL only the error message string is printed. .Pp The contents of the error message string is the same as those returned by .Fn strerror with argument .Fa errno . .Sh SEE ALSO .Xr intro 2 , .Xr psignal 3 , .Xr setlocale 3 , .Xr strerror 3 .Sh STANDARDS The .Fn perror function conforms to .St -ansiC .