mirror of https://github.com/mkerrisk/man-pages
166 lines
5.1 KiB
Groff
166 lines
5.1 KiB
Groff
.\" Copyright (C) 2006 Justin Pryzby <pryzbyj@justinpryzby.com>
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.\" and Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(PERMISSIVE_MISC)
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.\" Permission is hereby granted, free of charge, to any person obtaining
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.\" a copy of this software and associated documentation files (the
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.\" "Software"), to deal in the Software without restriction, including
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.\" without limitation the rights to use, copy, modify, merge, publish,
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.\" distribute, sublicense, and/or sell copies of the Software, and to
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.\" permit persons to whom the Software is furnished to do so, subject to
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.\" the following conditions:
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.\"
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.\" The above copyright notice and this permission notice shall be
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.\" included in all copies or substantial portions of the Software.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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.\" EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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.\" IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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.\" CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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.\" TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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.\" SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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.\" %%%LICENSE_END
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.\"
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.\" References:
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.\" glibc manual and source
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.TH ERROR 3 2017-09-15 "GNU" "Linux Programmer's Manual"
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.SH NAME
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error, error_at_line, error_message_count, error_one_per_line,
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error_print_progname \- glibc error reporting functions
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.SH SYNOPSIS
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.nf
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.B #include <error.h>
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.PP
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.BI "void error(int " status ", int " errnum ", const char *" format ", ...);"
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.PP
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.BI "void error_at_line(int " status ", int " errnum ", const char *" filename ,
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.BI " unsigned int " linenum ", const char *" format ", ...);"
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.PP
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.BI "extern unsigned int " error_message_count ;
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.PP
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.BI "extern int " error_one_per_line ;
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.PP
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.BI "extern void (*" error_print_progname ") (void);"
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.fi
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.SH DESCRIPTION
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.BR error ()
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is a general error-reporting function.
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It flushes
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.IR stdout ,
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and then outputs to
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.I stderr
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the program name, a colon and a space, the message specified by the
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.BR printf (3)-style
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format string \fIformat\fP, and, if \fIerrnum\fP is
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nonzero, a second colon and a space followed by the string given by
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.IR strerror(errnum) .
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Any arguments required for
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.I format
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should follow
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.I format
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in the argument list.
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The output is terminated by a newline character.
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.PP
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The program name printed by
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.BR error ()
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is the value of the global variable
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.BR program_invocation_name (3).
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.I program_invocation_name
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initially has the same value as
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.IR main ()'s
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.IR argv[0] .
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The value of this variable can be modified to change the output of
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.BR error ().
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.PP
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If \fIstatus\fP has a nonzero value, then
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.BR error ()
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calls
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.BR exit (3)
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to terminate the program using the given value as the exit status.
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.PP
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The
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.BR error_at_line ()
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function is exactly the same as
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.BR error (),
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except for the addition of the arguments
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.I filename
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and
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.IR linenum .
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The output produced is as for
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.BR error (),
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except that after the program name are written: a colon, the value of
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.IR filename ,
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a colon, and the value of
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.IR linenum .
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The preprocessor values \fB__LINE__\fP and
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\fB__FILE__\fP may be useful when calling
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.BR error_at_line (),
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but other values can also be used.
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For example, these arguments could refer to a location in an input file.
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.PP
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If the global variable \fIerror_one_per_line\fP is set nonzero,
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a sequence of
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.BR error_at_line ()
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calls with the
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same value of \fIfilename\fP and \fIlinenum\fP will result in only
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one message (the first) being output.
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.PP
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The global variable \fIerror_message_count\fP counts the number of
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messages that have been output by
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.BR error ()
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and
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.BR error_at_line ().
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.PP
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If the global variable \fIerror_print_progname\fP
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is assigned the address of a function
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(i.e., is not NULL), then that function is called
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instead of prefixing the message with the program name and colon.
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The function should print a suitable string to
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.IR stderr .
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.ad l
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.TS
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allbox;
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lb lb lbw33
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l l l.
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Interface Attribute Value
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T{
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.BR error ()
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T} Thread safety MT-Safe locale
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T{
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.BR error_at_line ()
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T} Thread safety T{
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MT-Unsafe\ race: error_at_line/error_one_per_line locale
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T}
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.TE
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.ad
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.PP
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The internal
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.I error_one_per_line
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variable is accessed (without any form of synchronization, but since it's an
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.I int
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used once, it should be safe enough) and, if
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.I error_one_per_line
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is set nonzero, the internal static variables (not exposed to users)
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used to hold the last printed filename and line number are accessed
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and modified without synchronization; the update is not atomic and it
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occurs before disabling cancellation, so it can be interrupted only after
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one of the two variables is modified.
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After that,
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.BR error_at_line ()
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is very much like
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.BR error ().
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.SH CONFORMING TO
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These functions and variables are GNU extensions, and should not be
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used in programs intended to be portable.
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.SH SEE ALSO
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.BR err (3),
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.BR errno (3),
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.BR exit (3),
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.BR perror (3),
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.BR program_invocation_name (3),
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.BR strerror (3)
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