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PERROR(3P)                 POSIX Programmer's Manual                PERROR(3P)
PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       perror -- write error messages to standard error
SYNOPSIS
       #include <stdio.h>
       void perror(const char *s);
DESCRIPTION
       The functionality described on this reference page is aligned with  the
       ISO C  standard.  Any  conflict between the requirements described here
       and the ISO C standard is unintentional. This  volume  of  POSIX.1-2008
       defers to the ISO C standard.
       The  perror()  function shall map the error number accessed through the
       symbol errno to a language-dependent  error  message,  which  shall  be
       written to the standard error stream as follows:
        *  First (if s is not a null pointer and the character pointed to by s
           is not the null byte), the string pointed to by  s  followed  by  a
           <colon> and a <space>.
        *  Then an error message string followed by a <newline>.
       The  contents  of  the error message strings shall be the same as those
       returned by strerror() with argument errno.
       The perror() function shall mark for update the last data  modification
       and  last file status change timestamps of the file associated with the
       standard error stream at some time between  its  successful  completion
       and  exit(),  abort(),  or  the  completion  of fflush() or fclose() on
       stderr.
       The perror() function shall not change the orientation of the  standard
       error stream.
       On  error,  perror()  shall  set  the error indicator for the stream to
       which stderr points, and shall set errno to indicate the error.
       Since no value is returned, an application wishing to check  for  error
       situations  should  call clearerr(stderr) before calling perror(), then
       if ferror(stderr) returns non-zero, the value of errno indicates  which
       error occurred.
RETURN VALUE
       The perror() function shall not return a value.
ERRORS
       Refer to fputc().
       The following sections are informative.
EXAMPLES
   Printing an Error Message for a Function
       The  following example replaces bufptr with a buffer that is the neces-
       sary size. If an error occurs, the perror() function prints  a  message
       and the program exits.
           #include <stdio.h>
           #include <stdlib.h>
           ...
           char *bufptr;
           size_t szbuf;
           ...
           if ((bufptr = malloc(szbuf)) == NULL) {
               perror("malloc"); exit(2);
           }
           ...
APPLICATION USAGE
       Application writers may prefer to use alternative interfaces instead of
       perror(), such as strerror_r() in combination with fprintf().
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       fprintf(), fputc(), psiginfo(), strerror()
       The Base Definitions volume of POSIX.1-2008, <stdio.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           PERROR(3P)