freopen(3ucb) [opensolaris man page]

fopen(3UCB)					     SunOS/BSD Compatibility Library Functions					       fopen(3UCB)

NAME

       fopen, freopen - open a stream

SYNOPSIS

       /usr/ucb/cc [ flag ... ] file ...
       #include <stdio.h>

       FILE *fopen(file, mode)
       const char *file, *mode;

       FILE *freopen(file, mode, iop)
       const char *file, *mode;
       register FILE *iop;

DESCRIPTION

       The  fopen()  function opens the file specified by file and associates a stream with it. If the open succeeds, fopen() returns a pointer to
       be used to identify the stream in subsequent operations. The file argument points to a character string that contains the name of the  file
       to be opened. The mode argument is a character string having one of the following values:

       r     open for reading

       w     truncate or create for writing

       a     append: open for writing at end of file, or create for writing

       r+    open for update (reading and writing)

       w+    truncate or create for update

       a+    append; open or create for update at EOF

       The freopen() function opens the file specified by file and associates the stream pointed to by iop with it. The mode argument is used just
       as in fopen(). The original stream is closed, regardless of whether the open ultimately succeeds. If the open succeeds,	freopen()  returns
       the original value of iop.

       The freopen() function is typically used to attach the preopened streams associated withstdin, stdout, and stderr to other files.

       When  a	file  is  opened for update, both input and output can be performed on the resulting stream. Output cannot be directly followed by
       input without an intervening fseek(3C) or rewind(3C). Input cannot be directly followed by  output  without  an	intervening  fseek(3C)	or
       rewind(3C). An input operation that encounters  EOF will fail.

RETURN VALUES

       The fopen() and freopen() functions return a NULL pointer on failure.

USAGE

       The fopen() and freopen() functions have transitional interfaces for 64-bit file offsets.  See lf64(5).

SEE ALSO

       cc(1B), open(2), fclose(3C), fopen(3C), freopen(3C), fseek(3C), malloc(3C), rewind(3C), lf64(5)

NOTES

       Use  of	these  functions  should  be  restricted  to applications written on BSD platforms.  Use of these functions with any of the system
       libraries or in multithreaded applications is unsupported.

       To support the same number of open files as the system, fopen() must allocate additional memory for data structures using malloc(3C)  after
       64 files have been opened. This confuses some programs that use their own memory allocators.

       The  fopen()  and  freopen() functions differ from the standard I/O functions fopen(3C) and freopen(3C). The standard I/O functions distin-
       guish binary from text files with an additional use of 'b' as part of the mode, enabling portability of fopen(3C)  and  freopen(3C)  beyond
       SunOS  4.x systems.

SunOS 5.11							    30 Oct 2007 						       fopen(3UCB)