STRERROR(3) | Library Functions Manual | STRERROR(3) |
perror
, strerror
,
strerror_r
, sys_errlist
,
sys_nerr
—
#include <stdio.h>
void
perror
(const
char *string);
#include
<errno.h>
extern const char * const sys_errlist[];
extern const int sys_nerr;
#include
<string.h>
char *
strerror
(int
errnum);
int
strerror_r
(int
errnum, char
*strerrbuf, size_t
buflen);
strerror
(), 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. Note that in most cases the
err(3) and
warn(3) family of functions is
preferable to perror
(); they are more flexible and
also print the program name.
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.
perror
() and strerror
()
functions conform to ISO/IEC 9899:1999
(“ISO C99”). The
strerror_r
() function conforms to
IEEE Std 1003.1-2001 (“POSIX.1”).
perror
() function first appeared in
Version 4 AT&T UNIX. The
strerror
() function first appeared in
4.3BSD-Reno. The strerror_r
()
function first appeared in NetBSD 4.0.
strerror
() 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 const char
*.
Programs that use the deprecated sys_errlist variable often fail to compile because they declare it inconsistently.
May 9, 2015 | NetBSD 9.2 |