mirror of https://github.com/mkerrisk/man-pages
182 lines
5.4 KiB
Groff
182 lines
5.4 KiB
Groff
.\" Copyright (C) 1993 David Metcalfe (david@prism.demon.co.uk)
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.\" and Copyright (C) 2005, Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 18:05:30 1993 by Rik Faith <faith@cs.unc.edu>
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.\" Modified Fri Feb 16 14:25:17 1996 by Andries Brouwer <aeb@cwi.nl>
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.\" Modified Sun Jul 21 20:55:44 1996 by Andries Brouwer <aeb@cwi.nl>
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.\" Modified Mon Oct 15 21:16:25 2001 by John Levon <moz@compsoc.man.ac.uk>
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.\" Modified Tue Oct 16 00:04:43 2001 by Andries Brouwer <aeb@cwi.nl>
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.\" Modified Fri Jun 20 03:04:30 2003 by Andries Brouwer <aeb@cwi.nl>
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.\" 2005-12-13, mtk, Substantial rewrite of strerror_r() description
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.\" Addition of extra material on portability and standards.
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.\"
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.TH STRERROR 3 2009-03-30 "" "Linux Programmer's Manual"
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.SH NAME
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strerror, strerror_r \- return string describing error number
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.SH SYNOPSIS
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.nf
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.B #include <string.h>
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.sp
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.BI "char *strerror(int " errnum );
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.sp
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.BI "int strerror_r(int " errnum ", char *" buf ", size_t " buflen );
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/* XSI-compliant */
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.sp
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.BI "char *strerror_r(int " errnum ", char *" buf ", size_t " buflen );
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/* GNU-specific */
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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The XSI-compliant version of
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.BR strerror_r ()
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is provided if:
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.br
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(_POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600) && !\ _GNU_SOURCE
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.br
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Otherwise, the GNU-specific version is provided.
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.SH DESCRIPTION
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The
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.BR strerror ()
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function returns a pointer to a string that describes the error
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code passed in the argument \fIerrnum\fP, possibly using the
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.B LC_MESSAGES
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part of the current locale to select the appropriate language.
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This string must not be modified by the application, but may be
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modified by a subsequent call to
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.BR perror (3)
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or
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.BR strerror ().
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No library function will modify this string.
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The
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.BR strerror_r ()
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function is similar to
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.BR strerror (),
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but is
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thread safe.
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This function is available in two versions:
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an XSI-compliant version specified in POSIX.1-2001
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(available since glibc 2.3.4),
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and a GNU-specific version (available since glibc 2.0).
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The XSI-compliant version is provided with the feature test macros
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settings shown in the SYNOPSIS;
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otherwise the GNU-specific version is provided.
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If no feature test macros are explicitly defined,
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then (since glibc 2.4)
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.B _POSIX_SOURCE
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is defined by default with the value
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200112L, so that the XSI-compliant version of
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.BR strerror_r ()
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is provided by default.
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The XSI-compliant
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.BR strerror_r ()
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is preferred for portable applications.
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It returns the error string in the user-supplied buffer
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.I buf
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of length
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.IR buflen .
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The GNU-specific
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.BR strerror_r ()
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returns a pointer to a string containing the error message.
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This may be either a pointer to a string that the function stores in
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.IR buf ,
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or a pointer to some (immutable) static string
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(in which case
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.I buf
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is unused).
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If the function stores a string in
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.IR buf ,
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then at most
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.I buflen
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bytes are stored (the string may be truncated if
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.I buflen
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is too small) and the string always includes a terminating null byte.
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.SH "RETURN VALUE"
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The
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.BR strerror ()
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and the GNU-specific
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.BR strerror_r ()
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functions return
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the appropriate error description string,
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or an "Unknown error nnn" message if the error number is unknown.
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The XSI-compliant
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.BR strerror_r ()
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function returns 0 on success;
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on error, \-1 is returned and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EINVAL
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The value of
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.I errnum
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is not a valid error number.
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.TP
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.B ERANGE
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Insufficient storage was supplied to contain the error description string.
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.SH "CONFORMING TO"
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.BR strerror ()
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is specified by POSIX.1-2001, C89, C99.
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.BR strerror_r ()
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is specified by POSIX.1-2001.
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The GNU-specific
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.BR strerror_r ()
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function is a nonstandard extension.
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POSIX.1-2001 permits
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.BR strerror ()
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to set
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.I errno
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if the call encounters an error, but does not specify what
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value should be returned as the function result in the event of an error.
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On some systems,
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.\" e.g., Solaris 8, HP-UX 11
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.BR strerror ()
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returns NULL if the error number is unknown.
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On other systems,
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.\" e.g., FreeBSD 5.4, Tru64 5.1B
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.BR strerror ()
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returns a string something like "Error nnn occurred" and sets
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.I errno
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to
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.B EINVAL
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if the error number is unknown.
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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 error (3),
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.BR perror (3),
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.BR strsignal (3)
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