1SETBUF(3P)                 POSIX Programmer's Manual                SETBUF(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       setbuf — assign buffering to a stream
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SYNOPSIS

15       #include <stdio.h>
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17       void setbuf(FILE *restrict stream, char *restrict buf);
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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       Except that it returns no value, the function call:
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28           setbuf(stream, buf)
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30       shall be equivalent to:
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33           setvbuf(stream, buf, _IOFBF, BUFSIZ)
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35       if buf is not a null pointer, or to:
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38           setvbuf(stream, buf, _IONBF, BUFSIZ)
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40       if buf is a null pointer.
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RETURN VALUE

43       The setbuf() function shall not return a value.
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ERRORS

46       Although  the  setvbuf()  interface  may set errno in defined ways, the
47       value of errno after a call to setbuf() is unspecified.
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49       The following sections are informative.
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EXAMPLES

52       None.
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APPLICATION USAGE

55       A common source of error is allocating buffer space as an ``automatic''
56       variable  in  a code block, and then failing to close the stream in the
57       same block.
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59       With setbuf(), allocating a buffer of BUFSIZ bytes does not necessarily
60       imply that all of BUFSIZ bytes are used for the buffer area.
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62       Since  errno  is  not  required to be unchanged on success, in order to
63       correctly detect and possibly recover from errors, applications  should
64       use setvbuf() instead of setbuf().
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RATIONALE

67       None.
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FUTURE DIRECTIONS

70       None.
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SEE ALSO

73       Section 2.5, Standard I/O Streams, fopen(), setvbuf()
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75       The Base Definitions volume of POSIX.1‐2017, <stdio.h>
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78       Portions  of  this text are reprinted and reproduced in electronic form
79       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
80       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
81       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
82       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
83       event of any discrepancy between this version and the original IEEE and
84       The  Open Group Standard, the original IEEE and The Open Group Standard
85       is the referee document. The original Standard can be  obtained  online
86       at http://www.opengroup.org/unix/online.html .
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88       Any  typographical  or  formatting  errors that appear in this page are
89       most likely to have been introduced during the conversion of the source
90       files  to  man page format. To report such errors, see https://www.ker‐
91       nel.org/doc/man-pages/reporting_bugs.html .
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95IEEE/The Open Group                  2017                           SETBUF(3P)
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