1STDIN(3P)                  POSIX Programmer's Manual                 STDIN(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

12       stderr, stdin, stdout — standard I/O streams
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SYNOPSIS

15       #include <stdio.h>
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17       extern FILE *stderr, *stdin, *stdout;
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DESCRIPTION

20       The functionality described on this reference page is aligned with  the
21       ISO C  standard.  Any  conflict between the requirements described here
22       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
23       defers to the ISO C standard.
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25       A  file with associated buffering is called a stream and is declared to
26       be a pointer to a defined type FILE.  The fopen() function shall create
27       certain descriptive data for a stream and return a pointer to designate
28       the stream in all further transactions. Normally, there are three  open
29       streams  with  constant  pointers  declared in the <stdio.h> header and
30       associated with the standard open files.
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32       At program start-up, three streams shall be predefined and need not  be
33       opened  explicitly:  standard  input  (for reading conventional input),
34       standard output (for writing conventional output), and  standard  error
35       (for writing diagnostic output). When opened, the standard error stream
36       is not fully buffered; the standard input and standard  output  streams
37       are  fully  buffered if and only if the stream can be determined not to
38       refer to an interactive device.
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40       The following symbolic values in <unistd.h> define the file descriptors
41       that  shall be associated with the C-language stdin, stdout, and stderr
42       when the application is started:
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44       STDIN_FILENO  Standard input value, stdin.  Its value is 0.
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46       STDOUT_FILENO Standard output value, stdout.  Its value is 1.
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48       STDERR_FILENO Standard error value, stderr.  Its value is 2.
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50       The stderr stream is expected to be open for reading and writing.
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RETURN VALUE

53       None.
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ERRORS

56       No errors are defined.
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58       The following sections are informative.
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EXAMPLES

61       None.
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APPLICATION USAGE

64       None.
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RATIONALE

67       None.
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FUTURE DIRECTIONS

70       None.
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SEE ALSO

73       fclose(), feof(),  ferror(),  fileno(),  fopen(),  fprintf(),  fread(),
74       fscanf(),  fseek(),  getc(),  gets(),  popen(), putc(), puts(), read(),
75       setbuf(), setvbuf(), tmpfile(), ungetc(), vfprintf()
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77       The Base Definitions volume of POSIX.1‐2017, <stdio.h>, <unistd.h>
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80       Portions of this text are reprinted and reproduced in  electronic  form
81       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
82       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
83       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
84       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
85       event of any discrepancy between this version and the original IEEE and
86       The Open Group Standard, the original IEEE and The Open Group  Standard
87       is  the  referee document. The original Standard can be obtained online
88       at http://www.opengroup.org/unix/online.html .
89
90       Any typographical or formatting errors that appear  in  this  page  are
91       most likely to have been introduced during the conversion of the source
92       files to man page format. To report such errors,  see  https://www.ker‐
93       nel.org/doc/man-pages/reporting_bugs.html .
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97IEEE/The Open Group                  2017                            STDIN(3P)
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