.\" Copyright (C) 1993 David Metcalfe (david@prism.demon.co.uk)
-.\" and 2005, Michael Kerrisk <mtk-manpages@gmx.net>
+.\" and Copyright (C) 2005, 2014 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
+.\" %%%LICENSE_START(VERBATIM)
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.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
-.\"
+.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
-.\"
+.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
.\"
.\" References consulted:
.\" Linux libc source code
.\" 2005-12-13, mtk, Substantial rewrite of strerror_r() description
.\" Addition of extra material on portability and standards.
.\"
-.TH STRERROR 3 2005-12-13 "" "Linux Programmer's Manual"
+.TH STRERROR 3 2017-09-15 "" "Linux Programmer's Manual"
.SH NAME
-strerror, strerror_r \- return string describing error number
+strerror, strerror_r, strerror_l \- return string describing error number
.SH SYNOPSIS
.nf
.B #include <string.h>
-.sp
+.PP
.BI "char *strerror(int " errnum );
-.sp
-.BI "char *strerror_r(int " errnum ", char *" buf ", size_t " buflen );
- /* GNU-specific strerror_r() */
-.sp
-.B #define _XOPEN_SOURCE 600
-.B #include <string.h>
-.sp
+.PP
.BI "int strerror_r(int " errnum ", char *" buf ", size_t " buflen );
- /* XSI-compliant strerror_r() */
+ /* XSI-compliant */
+.PP
+.BI "char *strerror_r(int " errnum ", char *" buf ", size_t " buflen );
+ /* GNU-specific */
+.PP
+.BI "char *strerror_l(int " errnum ", locale_t " locale );
.fi
+.PP
+.in -4n
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.in
+.ad l
+.PP
+.BR strerror_r ():
+.RS 4
+The XSI-compliant version is provided if:
+.br
+(_POSIX_C_SOURCE\ >=\ 200112L) && ! \ _GNU_SOURCE
+.br
+Otherwise, the GNU-specific version is provided.
+.RE
+.ad
.SH DESCRIPTION
-The \fBstrerror\fP() function returns a string describing the error
-code passed in the argument \fIerrnum\fP, possibly using the LC_MESSAGES
+The
+.BR strerror ()
+function returns a pointer to a string that describes the error
+code passed in the argument
+.IR errnum ,
+possibly using the
+.B LC_MESSAGES
part of the current locale to select the appropriate language.
+(For example, if
+.I errnum
+is
+.BR EINVAL ,
+the returned description will be "Invalid argument".)
This string must not be modified by the application, but may be
-modified by a subsequent call to \fBperror\fP() or \fBstrerror\fP().
-No library function will modify this string.
-
-The \fBstrerror_r\fP() function is similar to \fBstrerror\fP(), but is
-thread safe.
-This function is available in two versions:
-an XSI-compliant version specified in SUSv3,
+modified by a subsequent call to
+.BR strerror ()
+or
+.BR strerror_l ().
+No other library function, including
+.BR perror (3),
+will modify this string.
+.\"
+.SS strerror_r()
+The
+.BR strerror_r ()
+function is similar to
+.BR strerror (),
+but is
+thread safe.
+This function is available in two versions:
+an XSI-compliant version specified in POSIX.1-2001
+(available since glibc 2.3.4, but not POSIX-compliant until glibc 2.13),
and a GNU-specific version (available since glibc 2.0).
-If _XOPEN_SOURCE is defined with the value 600,
-then the XSI-compliant version is provided,
+The XSI-compliant version is provided with the feature test macros
+settings shown in the SYNOPSIS;
otherwise the GNU-specific version is provided.
-
-The XSI-compliant
-.BR strerror_r ()
+If no feature test macros are explicitly defined,
+then (since glibc 2.4)
+.B _POSIX_C_SOURCE
+is defined by default with the value
+200112L, so that the XSI-compliant version of
+.BR strerror_r ()
+is provided by default.
+.PP
+The XSI-compliant
+.BR strerror_r ()
is preferred for portable applications.
It returns the error string in the user-supplied buffer
.I buf
of length
.IR buflen .
-
-The GNU-specific
-.BR strerror_r ()
+.PP
+The GNU-specific
+.BR strerror_r ()
returns a pointer to a string containing the error message.
This may be either a pointer to a string that the function stores in
.IR buf ,
or a pointer to some (immutable) static string
(in which case
-.I buf
+.I buf
is unused).
-If the function stores a string in
+If the function stores a string in
.IR buf ,
then at most
.I buflen
bytes are stored (the string may be truncated if
.I buflen
-is too small) and the string always includes a terminating null byte.
-
-.SH "RETURN VALUE"
-The \fBstrerror\fP() and \fBstrerror_r\fP() functions return
-the appropriate error description string,
+is too small and
+.I errnum
+is unknown).
+The string always includes a terminating null byte (\(aq\\0\(aq).
+.\"
+.SS strerror_l()
+.BR strerror_l ()
+is like
+.BR strerror (),
+but maps
+.I errnum
+to a locale-dependent error message in the locale specified by
+.IR locale .
+The behavior of
+.BR strerror_l ()
+is undefined if
+.I locale
+is the special locale object
+.BR LC_GLOBAL_LOCALE
+or is not a valid locale object handle.
+.SH RETURN VALUE
+The
+.BR strerror (),
+.BR strerror_l (),
+and the GNU-specific
+.BR strerror_r ()
+functions return
+the appropriate error description string,
or an "Unknown error nnn" message if the error number is unknown.
-
-The XSI-compliant \fBstrerror_r\fP() function returns 0 on success;
-on error, \-1 is returned and
+.PP
+The XSI-compliant
+.BR strerror_r ()
+function returns 0 on success.
+On error,
+a (positive) error number is returned (since glibc 2.13),
+or \-1 is returned and
+.I errno
+is set to indicate the error (glibc versions before 2.13).
+.PP
+POSIX.1-2001 and POSIX.1-2008 require that a successful call to
+.BR strerror ()
+or
+.BR strerror_l ()
+shall leave
.I errno
-is set to indicate the error.
-
+unchanged, and note that,
+since no function return value is reserved to indicate an error,
+an application that wishes to check for errors should initialize
+.I errno
+to zero before the call,
+and then check
+.I errno
+after the call.
.SH ERRORS
.TP
.B EINVAL
.TP
.B ERANGE
Insufficient storage was supplied to contain the error description string.
-
-.SH "CONFORMING TO"
-POSIX.1
-
-The GNU-specific
+.SH VERSIONS
+The
+.BR strerror_l ()
+function first appeared in glibc 2.6.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw14 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR strerror ()
+T} Thread safety MT-Unsafe race:strerror
+T{
+.BR strerror_r (),
+.br
+.BR strerror_l ()
+T} Thread safety MT-Safe
+.TE
+.SH CONFORMING TO
+.BR strerror ()
+is specified by POSIX.1-2001, POSIX.1-2008, C89, and C99.
.BR strerror_r ()
-function is a non-standard extension.
-
-POSIX.1 permits
+is specified by POSIX.1-2001 and POSIX.1-2008.
+.\" FIXME . for later review when Issue 8 is one day released...
+.\" A future POSIX.1 may remove strerror_r()
+.\" http://austingroupbugs.net/tag_view_page.php?tag_id=8
+.\" http://austingroupbugs.net/view.php?id=508
+.PP
+.BR strerror_l ()
+is specified in POSIX.1-2008.
+.PP
+The GNU-specific
+.BR strerror_r ()
+function is a nonstandard extension.
+.PP
+POSIX.1-2001 permits
.BR strerror ()
-to set
+to set
.I errno
-if the call encounters an error, but does not specify what
+if the call encounters an error, but does not specify what
value should be returned as the function result in the event of an error.
On some systems,
.\" e.g., Solaris 8, HP-UX 11
.BR strerror ()
returns NULL if the error number is unknown.
-On other systems,
+On other systems,
.\" e.g., FreeBSD 5.4, Tru64 5.1B
.BR strerror ()
-returns a string something like "Error nnn occurred" and sets
+returns a string something like "Error nnn occurred" and sets
.I errno
-to
+to
.B EINVAL
if the error number is unknown.
-
-.SH "SEE ALSO"
+C99 and POSIX.1-2008 require the return value to be non-NULL.
+.SH NOTES
+The GNU C Library uses a buffer of 1024 characters for
+.BR strerror ().
+This buffer size therefore should be sufficient to avoid an
+.B ERANGE
+error when calling
+.BR strerror_r ()
+and
+.BR strerror_l ().
+.SH SEE ALSO
.BR err (3),
.BR errno (3),
+.BR error (3),
.BR perror (3),
-.BR strsignal (3)
+.BR strsignal (3),
+.BR locale (7)
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