1STRERROR(3) Linux Programmer's Manual STRERROR(3)
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6 strerror, strerror_r - return string describing error number
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9 #include <string.h>
10 char *strerror(int errnum);
12 int strerror_r(int errnum, char *buf, size_t buflen);
14 /* XSI-compliant */
15 char *strerror_r(int errnum, char *buf, size_t buflen);
17 /* GNU-specific */
18 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
20 The XSI-compliant version of strerror_r() is provided if:
22 (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && ! _GNU_SOURCE
23 Otherwise, the GNU-specific version is provided.
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26 The strerror() function returns a pointer to a string that describes
27 the error code passed in the argument errnum, possibly using the
28 LC_MESSAGES part of the current locale to select the appropriate lan‐
29 guage. This string must not be modified by the application, but may be
30 modified by a subsequent call to perror(3) or strerror(). No library
31 function will modify this string.
32 The strerror_r() function is similar to strerror(), but is thread safe.
34 This function is available in two versions: an XSI-compliant version
35 specified in POSIX.1-2001 (available since glibc 2.3.4), and a GNU-spe‐
36 cific version (available since glibc 2.0). The XSI-compliant version
37 is provided with the feature test macros settings shown in the SYNOP‐
38 SIS; otherwise the GNU-specific version is provided. If no feature
39 test macros are explicitly defined, then (since glibc 2.4)
40 _POSIX_SOURCE is defined by default with the value 200112L, so that the
41 XSI-compliant version of strerror_r() is provided by default.
42 The XSI-compliant strerror_r() is preferred for portable applications.
44 It returns the error string in the user-supplied buffer buf of length
45 buflen.
46 The GNU-specific strerror_r() returns a pointer to a string containing
48 the error message. This may be either a pointer to a string that the
49 function stores in buf, or a pointer to some (immutable) static string
50 (in which case buf is unused). If the function stores a string in buf,
51 then at most buflen bytes are stored (the string may be truncated if
52 buflen is too small) and the string always includes a terminating null
53 byte.
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56 The strerror() and the GNU-specific strerror_r() functions return the
57 appropriate error description string, or an "Unknown error nnn" message
58 if the error number is unknown.
59 The XSI-compliant strerror_r() function returns 0 on success; on error,
61 -1 is returned and errno is set to indicate the error.
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64 EINVAL The value of errnum is not a valid error number.
65 ERANGE Insufficient storage was supplied to contain the error descrip‐
67 tion string.
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70 strerror() is specified by POSIX.1-2001, C89, C99. strerror_r() is
71 specified by POSIX.1-2001.
72 The GNU-specific strerror_r() function is a nonstandard extension.
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