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fea681da | 1 | .\" Copyright (C) 1993 David Metcalfe (david@prism.demon.co.uk) |
c11b1abf | 2 | .\" and Copyright (C) 2005, Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da MK |
3 | .\" |
4 | .\" Permission is granted to make and distribute verbatim copies of this | |
5 | .\" manual provided the copyright notice and this permission notice are | |
6 | .\" preserved on all copies. | |
7 | .\" | |
8 | .\" Permission is granted to copy and distribute modified versions of this | |
9 | .\" manual under the conditions for verbatim copying, provided that the | |
10 | .\" entire resulting derived work is distributed under the terms of a | |
11 | .\" permission notice identical to this one. | |
c13182ef | 12 | .\" |
fea681da MK |
13 | .\" Since the Linux kernel and libraries are constantly changing, this |
14 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
15 | .\" responsibility for errors or omissions, or for damages resulting from | |
16 | .\" the use of the information contained herein. The author(s) may not | |
17 | .\" have taken the same level of care in the production of this manual, | |
18 | .\" which is licensed free of charge, as they might when working | |
19 | .\" professionally. | |
c13182ef | 20 | .\" |
fea681da MK |
21 | .\" Formatted or processed versions of this manual, if unaccompanied by |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
23 | .\" | |
24 | .\" References consulted: | |
25 | .\" Linux libc source code | |
26 | .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) | |
27 | .\" 386BSD man pages | |
28 | .\" Modified Sat Jul 24 18:05:30 1993 by Rik Faith <faith@cs.unc.edu> | |
29 | .\" Modified Fri Feb 16 14:25:17 1996 by Andries Brouwer <aeb@cwi.nl> | |
30 | .\" Modified Sun Jul 21 20:55:44 1996 by Andries Brouwer <aeb@cwi.nl> | |
31 | .\" Modified Mon Oct 15 21:16:25 2001 by John Levon <moz@compsoc.man.ac.uk> | |
32 | .\" Modified Tue Oct 16 00:04:43 2001 by Andries Brouwer <aeb@cwi.nl> | |
33 | .\" Modified Fri Jun 20 03:04:30 2003 by Andries Brouwer <aeb@cwi.nl> | |
ed07f09a MK |
34 | .\" 2005-12-13, mtk, Substantial rewrite of strerror_r() description |
35 | .\" Addition of extra material on portability and standards. | |
fea681da | 36 | .\" |
a5fa6dfd | 37 | .TH STRERROR 3 2012-04-22 "" "Linux Programmer's Manual" |
fea681da | 38 | .SH NAME |
6e84dfa1 | 39 | strerror, strerror_r \- return string describing error number |
fea681da MK |
40 | .SH SYNOPSIS |
41 | .nf | |
42 | .B #include <string.h> | |
43 | .sp | |
44 | .BI "char *strerror(int " errnum ); | |
b99cf1e0 | 45 | .sp |
2d50dd9e MK |
46 | .BI "int strerror_r(int " errnum ", char *" buf ", size_t " buflen ); |
47 | /* XSI-compliant */ | |
48 | .sp | |
6e84dfa1 | 49 | .BI "char *strerror_r(int " errnum ", char *" buf ", size_t " buflen ); |
2d50dd9e | 50 | /* GNU-specific */ |
cc4615cc | 51 | .fi |
6e84dfa1 | 52 | .sp |
cc4615cc MK |
53 | .in -4n |
54 | Feature Test Macro Requirements for glibc (see | |
55 | .BR feature_test_macros (7)): | |
56 | .in | |
b99cf1e0 | 57 | .sp |
cc4615cc MK |
58 | The XSI-compliant version of |
59 | .BR strerror_r () | |
60 | is provided if: | |
61 | .br | |
98dbe7af | 62 | (_POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600) && !\ _GNU_SOURCE |
2d50dd9e MK |
63 | .br |
64 | Otherwise, the GNU-specific version is provided. | |
fea681da | 65 | .SH DESCRIPTION |
60a90ecd MK |
66 | The |
67 | .BR strerror () | |
c9980d2e | 68 | function returns a pointer to a string that describes the error |
ec5a588f MK |
69 | code passed in the argument \fIerrnum\fP, possibly using the |
70 | .B LC_MESSAGES | |
fea681da MK |
71 | part of the current locale to select the appropriate language. |
72 | This string must not be modified by the application, but may be | |
60a90ecd | 73 | modified by a subsequent call to |
60a90ecd | 74 | .BR strerror (). |
8ca6ceb0 EB |
75 | No library function, including |
76 | .BR perror (3), | |
77 | will modify this string. | |
fea681da | 78 | |
60a90ecd MK |
79 | The |
80 | .BR strerror_r () | |
81 | function is similar to | |
82 | .BR strerror (), | |
83 | but is | |
c13182ef MK |
84 | thread safe. |
85 | This function is available in two versions: | |
cc4615cc | 86 | an XSI-compliant version specified in POSIX.1-2001 |
8ca6ceb0 | 87 | (available since glibc 2.3.4, but not POSIX-compliant until glibc 2.13), |
6e84dfa1 | 88 | and a GNU-specific version (available since glibc 2.0). |
cc4615cc MK |
89 | The XSI-compliant version is provided with the feature test macros |
90 | settings shown in the SYNOPSIS; | |
6e84dfa1 | 91 | otherwise the GNU-specific version is provided. |
cc4615cc MK |
92 | If no feature test macros are explicitly defined, |
93 | then (since glibc 2.4) | |
0daa9e92 | 94 | .B _POSIX_SOURCE |
cc4615cc MK |
95 | is defined by default with the value |
96 | 200112L, so that the XSI-compliant version of | |
97 | .BR strerror_r () | |
98 | is provided by default. | |
6e84dfa1 | 99 | |
c13182ef MK |
100 | The XSI-compliant |
101 | .BR strerror_r () | |
6e84dfa1 MK |
102 | is preferred for portable applications. |
103 | It returns the error string in the user-supplied buffer | |
fea681da MK |
104 | .I buf |
105 | of length | |
6e84dfa1 MK |
106 | .IR buflen . |
107 | ||
c13182ef MK |
108 | The GNU-specific |
109 | .BR strerror_r () | |
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110 | returns a pointer to a string containing the error message. |
111 | This may be either a pointer to a string that the function stores in | |
112 | .IR buf , | |
113 | or a pointer to some (immutable) static string | |
114 | (in which case | |
c13182ef | 115 | .I buf |
6e84dfa1 | 116 | is unused). |
c13182ef | 117 | If the function stores a string in |
6e84dfa1 MK |
118 | .IR buf , |
119 | then at most | |
120 | .I buflen | |
121 | bytes are stored (the string may be truncated if | |
122 | .I buflen | |
8ca6ceb0 EB |
123 | is too small and |
124 | .I errnum | |
125 | is unknown). | |
126 | The string always includes a terminating null byte. | |
fea681da | 127 | .SH "RETURN VALUE" |
60a90ecd MK |
128 | The |
129 | .BR strerror () | |
2d50dd9e | 130 | and the GNU-specific |
60a90ecd MK |
131 | .BR strerror_r () |
132 | functions return | |
c13182ef | 133 | the appropriate error description string, |
6e84dfa1 | 134 | or an "Unknown error nnn" message if the error number is unknown. |
6e84dfa1 | 135 | |
f2682520 MK |
136 | POSIX.1-2001 and POSIX.1-2008 require that a successful call to |
137 | .BR strerror (3) | |
138 | shall leave | |
139 | .I errno | |
140 | unchanged, and note that, | |
141 | since no function return value is reserved to indicate an error, | |
142 | an application that wishes to check for errors should initialize | |
143 | .I errno | |
144 | to zero before the call, | |
145 | and then check | |
146 | .I errno | |
147 | after the call. | |
148 | ||
60a90ecd MK |
149 | The XSI-compliant |
150 | .BR strerror_r () | |
8ca6ceb0 EB |
151 | function returns 0 on success. |
152 | On error, | |
153 | a (positive) error number is returned (since glibc 2.13), | |
154 | or \-1 is returned and | |
155 | .I errno | |
156 | is set to indicate the error (glibc versions before 2.13). | |
fea681da MK |
157 | .SH ERRORS |
158 | .TP | |
159 | .B EINVAL | |
160 | The value of | |
161 | .I errnum | |
162 | is not a valid error number. | |
163 | .TP | |
164 | .B ERANGE | |
165 | Insufficient storage was supplied to contain the error description string. | |
fea681da | 166 | .SH "CONFORMING TO" |
60a90ecd MK |
167 | .BR strerror () |
168 | is specified by POSIX.1-2001, C89, C99. | |
169 | .BR strerror_r () | |
170 | is specified by POSIX.1-2001. | |
6e84dfa1 | 171 | |
c13182ef | 172 | The GNU-specific |
63aa9df0 | 173 | .BR strerror_r () |
c8f2dd47 | 174 | function is a nonstandard extension. |
6e84dfa1 | 175 | |
68e1685c | 176 | POSIX.1-2001 permits |
6e84dfa1 | 177 | .BR strerror () |
c13182ef | 178 | to set |
6e84dfa1 | 179 | .I errno |
c13182ef | 180 | if the call encounters an error, but does not specify what |
6e84dfa1 MK |
181 | value should be returned as the function result in the event of an error. |
182 | On some systems, | |
183 | .\" e.g., Solaris 8, HP-UX 11 | |
184 | .BR strerror () | |
185 | returns NULL if the error number is unknown. | |
c13182ef | 186 | On other systems, |
6e84dfa1 MK |
187 | .\" e.g., FreeBSD 5.4, Tru64 5.1B |
188 | .BR strerror () | |
c13182ef | 189 | returns a string something like "Error nnn occurred" and sets |
6e84dfa1 | 190 | .I errno |
c13182ef | 191 | to |
6e84dfa1 MK |
192 | .B EINVAL |
193 | if the error number is unknown. | |
8ca6ceb0 | 194 | C99 and POSIX.1-2008 require the return value to be non-NULL. |
fea681da | 195 | .SH "SEE ALSO" |
d7871cf9 | 196 | .BR err (3), |
fea681da | 197 | .BR errno (3), |
37b6aec3 | 198 | .BR error (3), |
fea681da | 199 | .BR perror (3), |
cc4615cc | 200 | .BR strsignal (3) |