strerror(3) - NetBSD Manual Pages

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STRERROR(3)             NetBSD Library Functions Manual            STRERROR(3)


NAME

     perror, strerror, strerror_r, sys_errlist, sys_nerr -- system error mes-
     sages


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #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);


DESCRIPTION

     The strerror(), strerror_r(), and perror() functions look up the lan-
     guage-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 cur-
     rent value of the global variable errno (intro(2)) and writes it, fol-
     lowed by a newline, to the standard error file descriptor.  If the argu-
     ment 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 func-
     tions 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 mes-
     sage 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 implemen-
     tation 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 mes-
     sages in sys_errlist.  The use of these variables is deprecated;
     strerror() or strerror_r() should be used instead.


SEE ALSO

     intro(2), err(3), psignal(3), warn(3)


STANDARDS

     The 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'').


HISTORY

     The 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.


BUGS

     For unknown error numbers, the 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 com-
     pile because they declare it inconsistently.

NetBSD 8.0                        May 9, 2015                       NetBSD 8.0