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+.\" Copyright (c) 1994 Michael Haardt (michael@moria.de), 1994-06-04
+.\" Copyright (c) 1995 Michael Haardt
+.\"      (michael@cantor.informatik.rwth-aachen.de), 1995-03-16
+.\" Copyright (c) 1996 Andries Brouwer (aeb@cwi.nl), 1996-01-13
+.\"
+.\" This is free documentation; you can redistribute it and/or
+.\" modify it under the terms of the GNU General Public License as
+.\" published by the Free Software Foundation; either version 2 of
+.\" the License, or (at your option) any later version.
+.\"
+.\" The GNU General Public License's references to "object code"
+.\" and "executables" are to be interpreted as the output of any
+.\" document formatting or typesetting system, including
+.\" intermediate and printed output.
+.\"
+.\" This manual is distributed in the hope that it will be useful,
+.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
+.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+.\" GNU General Public License for more details.
+.\"
+.\" You should have received a copy of the GNU General Public
+.\" License along with this manual; if not, write to the Free
+.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
+.\" USA.
+.\"
+.\" 1996-01-13 aeb: merged in some text contributed by Melvin Smith
+.\"   (msmith@falcon.mercer.peachnet.edu) and various other changes.
+.\" Modified 1996-05-16 by Martin Schulze (joey@infodrom.north.de)
+.\"
+.TH PERROR 3 2001-12-14 "" "Library functions"
+.SH NAME
+perror \- print a system error message
+.SH SYNOPSIS
+.B #include <stdio.h>
+.sp
+.BI "void perror(const char " *s );
+.sp
+.B #include <errno.h>
+.sp
+.BI "const char *" sys_errlist [];
+.br
+.BI "int " sys_nerr ;
+.br
+.BI "int " errno ;
+.SH DESCRIPTION
+The routine
+.B perror()
+produces a message on the standard error output, describing the last
+error encountered during a call to a system or library function.
+First (if
+.I s
+is not NULL and
+.RI * s
+is not NUL) the argument string
+.I s
+is printed, followed by a colon and a blank.
+Then the message and a new-line.
+
+To be of most use, the argument string should include the name
+of the function that incurred the error.  The error number is taken from
+the external variable
+.IR errno ,
+which is set when errors occur but not
+cleared when non-erroneous calls are made.
+
+The global error list
+.IR sys_errlist "[]"
+indexed by
+.I errno
+can be used to obtain the error message without the newline.
+The largest message number provided in the table is
+.IR sys_nerr " \-1."
+Be careful when directly accessing this list because new error values
+may not have been added to
+.IR sys_errlist "[]."
+
+When a system call fails, it usually returns \-1 and sets the
+variable
+.I errno
+to a value describing what went wrong. (These values can be found in
+.IR "<errno.h>" .)
+Many library functions do likewise.
+The function
+.B perror()
+serves to translate this error code into human-readable form.
+Note that
+.I errno
+is undefined after a successful library call:
+this call may well change this variable, even though it succeeds,
+for example because it internally used some other library function that failed.
+Thus, if a failing call is not immediately followed by a call to
+.BR perror ,
+the value of
+.I errno
+should be saved.
+
+.SH "CONFORMING TO"
+The function
+.B perror()
+and the external
+.I errno
+(see
+.BR errno (3))
+conform to ANSI C, BSD 4.3, POSIX, X/OPEN.
+The externals
+.I sys_nerr
+and
+.I sys_errlist
+conform to BSD.
+.SH NOTE
+The externals
+.I sys_nerr
+and
+.I sys_errlist
+are defined by glibc, but in
+.IR <stdio.h> .
+.\" and only when _BSD_SOURCE is defined.
+.\" When _GNU_SOURCE is defined, the symbols
+.\" .I _sys_nerr
+.\" and
+.\" .I _sys_errlist
+.\" are provided.
+.SH "SEE ALSO"
+.BR errno (3),
+.BR strerror (3)