void
perror(const char *string)
char *
strerror(int errnum)
int
strerror_r(int errnum, char *strerrbuf, size_t buflen)
),
strerror_r(),
and
perror()
functions look up the language-dependent error message
string corresponding to an error number.
The
strerror()
function accepts an error number argument
errnum
and returns a pointer to the corresponding
message string.
The
strerror_r()
function renders the same result into
strerrbuf
for a maximum of
buflen
characters and returns 0 upon success.
The
perror()
function finds the error message corresponding to the current
value of the global variable
errno
(intro(2))
and writes it, followed by a newline, to the
standard error file descriptor.
If the argument
string
is
non-NULL
and does not point to the nul character,
this string is prepended to the message
string and separated from it by
a colon and space
(``: '');
otherwise, only the error message string is printed.
If the error number is not recognized, these functions pass an error message
string containing
``Unknown error: ''
followed by the error number in decimal.
To warn about this,
strerror()
sets
errno
to
EINVAL,
and
strerror_r()
returns
EINVAL.
Error numbers recognized by this implementation fall in
the range 0 <
errnum
<
sys_nerr.
If insufficient storage is provided in
strerrbuf
(as specified in
buflen)
to contain the error string,
strerror_r()
returns
ERANGE
and
strerrbuf
will contain an error message that has been truncated and
NUL
terminated to fit the length specified by
buflen.
The message strings can be accessed directly using the external
array
sys_errlist.
The external value
sys_nerr
contains a count of the messages in
sys_errlist.
The use of these variables is deprecated;
strerror()
or
strerror_r()
should be used instead.
)
and
strerror()
functions conform to
ISO/IEC 9899:1999 (``ISO C99'') .
The
strerror_r()
function conforms to
IEEE Std 1003.1-2001 (``POSIX.1'') .
)
and
perror()
functions first appeared in
4.4BSD.
The
strerror_r()
function first appeared in
NetBSD4.0.
)
function will return its result in a static buffer which
may be overwritten by subsequent calls.
The return type for
strerror()
is missing a type-qualifier; it should actually be
Programs that use the deprecated sys_errlist variable often fail to compile because they declare it inconsistently.