1PERROR(3P)                 POSIX Programmer's Manual                PERROR(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

13       perror — write error messages to standard error
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SYNOPSIS

16       #include <stdio.h>
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18       void perror(const char *s);
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DESCRIPTION

21       The functionality described on this reference page is aligned with  the
22       ISO C  standard.  Any  conflict between the requirements described here
23       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2008
24       defers to the ISO C standard.
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26       The  perror()  function shall map the error number accessed through the
27       symbol errno to a language-dependent  error  message,  which  shall  be
28       written to the standard error stream as follows:
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30        *  First (if s is not a null pointer and the character pointed to by s
31           is not the null byte), the string pointed to by  s  followed  by  a
32           <colon> and a <space>.
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34        *  Then an error message string followed by a <newline>.
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36       The  contents  of  the error message strings shall be the same as those
37       returned by strerror() with argument errno.
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39       The perror() function shall mark for update the last data  modification
40       and  last file status change timestamps of the file associated with the
41       standard error stream at some time between  its  successful  completion
42       and  exit(),  abort(),  or  the  completion  of fflush() or fclose() on
43       stderr.
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45       The perror() function shall not change the orientation of the  standard
46       error stream.
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48       On  error,  perror()  shall  set  the error indicator for the stream to
49       which stderr points, and shall set errno to indicate the error.
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51       Since no value is returned, an application wishing to check  for  error
52       situations  should  call clearerr(stderr) before calling perror(), then
53       if ferror(stderr) returns non-zero, the value of errno indicates  which
54       error occurred.
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RETURN VALUE

57       The perror() function shall not return a value.
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ERRORS

60       Refer to fputc().
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62       The following sections are informative.
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EXAMPLES

65   Printing an Error Message for a Function
66       The  following example replaces bufptr with a buffer that is the neces‐
67       sary size. If an error occurs, the perror() function prints  a  message
68       and the program exits.
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70           #include <stdio.h>
71           #include <stdlib.h>
72           ...
73           char *bufptr;
74           size_t szbuf;
75           ...
76           if ((bufptr = malloc(szbuf)) == NULL) {
77               perror("malloc"); exit(2);
78           }
79           ...
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APPLICATION USAGE

82       Application writers may prefer to use alternative interfaces instead of
83       perror(), such as strerror_r() in combination with fprintf().
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RATIONALE

86       None.
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FUTURE DIRECTIONS

89       None.
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SEE ALSO

92       fprintf(), fputc(), psiginfo(), strerror()
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94       The Base Definitions volume of POSIX.1‐2008, <stdio.h>
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97       Portions of this text are reprinted and reproduced in  electronic  form
98       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
99       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
100       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
101       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
102       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
103       event of any discrepancy between this version and the original IEEE and
104       The  Open Group Standard, the original IEEE and The Open Group Standard
105       is the referee document. The original Standard can be  obtained  online
106       at http://www.unix.org/online.html .
107
108       Any  typographical  or  formatting  errors that appear in this page are
109       most likely to have been introduced during the conversion of the source
110       files  to  man page format. To report such errors, see https://www.ker
111       nel.org/doc/man-pages/reporting_bugs.html .
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115IEEE/The Open Group                  2013                           PERROR(3P)
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