1FILENO(P)                  POSIX Programmer's Manual                 FILENO(P)
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NAME

6       fileno - map a stream pointer to a file descriptor
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SYNOPSIS

9       #include <stdio.h>
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11       int fileno(FILE *stream);
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DESCRIPTION

15       The  fileno() function shall return the integer file descriptor associ‐
16       ated with the stream pointed to by stream.
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RETURN VALUE

19       Upon successful completion, fileno() shall return the integer value  of
20       the  file  descriptor  associated with stream.  Otherwise, the value -1
21       shall be returned and errno set to indicate the error.
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ERRORS

24       The fileno() function may fail if:
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26       EBADF  The stream argument is not a valid stream.
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29       The following sections are informative.
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EXAMPLES

32       None.
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APPLICATION USAGE

35       None.
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RATIONALE

38       Without some specification of which  file  descriptors  are  associated
39       with  these  streams, it is impossible for an application to set up the
40       streams for another application it starts with fork() and exec. In par‐
41       ticular, it would not be possible to write a portable version of the sh
42       command interpreter (although there may be other constraints that would
43       prevent that portability).
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FUTURE DIRECTIONS

46       None.
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SEE ALSO

49       Interaction  of  File Descriptors and Standard I/O Streams , fdopen() ,
50       fopen()   ,   stdin()   ,    the    Base    Definitions    volume    of
51       IEEE Std 1003.1-2001, <stdio.h>
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54       Portions  of  this text are reprinted and reproduced in electronic form
55       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
56       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
57       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
58       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
59       event of any discrepancy between this version and the original IEEE and
60       The  Open Group Standard, the original IEEE and The Open Group Standard
61       is the referee document. The original Standard can be  obtained  online
62       at http://www.opengroup.org/unix/online.html .
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66IEEE/The Open Group                  2003                            FILENO(P)
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