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fdopen(3c) [opensolaris man page]

fdopen(3C)						   Standard C Library Functions 						fdopen(3C)

NAME
fdopen - associate a stream with a file descriptor SYNOPSIS
#include <stdio.h> FILE *fdopen(int fildes, const char *mode); DESCRIPTION
The fdopen() function associates a stream with a file descriptor fildes. The mode argument is a character string having one of the following values: r or rb Open a file for reading. w or wb Open a file for writing. a or ab Open a file for writing at end of file. r+, rb+ or r+b Open a file for update (reading and writing). w+, wb+ or w+b Open a file for update (reading and writing). a+, ab+ or a+b Open a file for update (reading and writing) at end of file. The meaning of these flags is exactly as specified for the fopen(3C) function, except that modes beginning with w do not cause truncation of the file. A trailing F character can also be included in the mode argument as described in fopen(3C) to enable extended FILE facility. The mode of the stream must be allowed by the file access mode of the open file. The file position indicator associated with the new stream is set to the position indicated by the file offset associated with the file descriptor. The fdopen() function preserves the offset maximum previously set for the open file description corresponding to fildes. The error and end-of-file indicators for the stream are cleared. The fdopen() function may cause the st_atime field of the underlying file to be marked for update. If fildes refers to a shared memory object, the result of the fdopen() function is unspecified. RETURN VALUES
Upon successful completion, fdopen() returns a pointer to a stream. Otherwise, a null pointer is returned and errno is set to indicate the error. The fdopen() function may fail and not set errno if there are no free stdio streams. ERRORS
The fdopen() function may fail if: EBADF The fildes argument is not a valid file descriptor. EINVAL The mode argument is not a valid mode. EMFILE {FOPEN_MAX} streams are currently open in the calling process. {STREAM_MAX} streams are currently open in the calling process. ENOMEM There is insufficient space to allocate a buffer. USAGE
A process is allowed to have at least {FOPEN_MAX} stdio streams open at a time. For 32-bit applications, however, the underlying ABIs for- merly required that no file descriptor used to access the file underlying a stdio stream have a value greater than 255. To maintain binary compatibility with earlier Solaris releases, this limit still constrains 32-bit applications. File descriptors are obtained from calls like open(2), dup(2), creat(2) or pipe(2), which open files but do not return streams. Streams are necessary input for almost all of the standard I/O library functions. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |See below. | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ The F character in the mode argument is Evolving. In all other respects this function is Standard. SEE ALSO
creat(2), dup(2), open(2), pipe(2), fclose(3C), fopen(3C), attributes(5), standards(5) SunOS 5.11 18 Apr 2006 fdopen(3C)

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FOPEN(3)						     Linux Programmer's Manual							  FOPEN(3)

NAME
fopen, fdopen, freopen - stream open functions SYNOPSIS
#include <stdio.h> FILE *fopen(const char *path, const char *mode); FILE *fdopen(int fildes, const char *mode); FILE *freopen(const char *path, const char *mode, FILE *stream); DESCRIPTION
The fopen function opens the file whose name is the string pointed to by path and associates a stream with it. The argument mode points to a string beginning with one of the following sequences (Additional characters may follow these sequences.): r Open text file for reading. The stream is positioned at the beginning of the file. r+ Open for reading and writing. The stream is positioned at the beginning of the file. w Truncate file to zero length or create text file for writing. The stream is positioned at the beginning of the file. w+ Open for reading and writing. The file is created if it does not exist, otherwise it is truncated. The stream is positioned at the beginning of the file. a Open for appending (writing at end of file). The file is created if it does not exist. The stream is positioned at the end of the file. a+ Open for reading and appending (writing at end of file). The file is created if it does not exist. The stream is positioned at the end of the file. The mode string can also include the letter ``b'' either as a last character or as a character between the characters in any of the two- character strings described above. This is strictly for compatibility with ANSI X3.159-1989 (``ANSI C'') and has no effect; the ``b'' is ignored on all POSIX conforming systems, including Linux. (Other systems may treat text files and binary files differently, and adding the ``b'' may be a good idea if you do I/O to a binary file and expect that your program may be ported to non-Unix environments.) Any created files will have mode S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH (0666), as modified by the process' umask value (see umask(2)). Reads and writes may be intermixed on read/write streams in any order. Note that ANSI C requires that a file positioning function inter- vene between output and input, unless an input operation encounters end-of-file. (If this condition is not met, then a read is allowed to return the result of writes other than the most recent.) Therefore it is good practice (and indeed sometimes necessary under Linux) to put an fseek or fgetpos operation between write and read operations on such a stream. This operation may be an apparent no-op (as in fseek(..., 0L, SEEK_CUR) called for its synchronizing side effect. Opening a file in append mode (a as the first character of mode) causes all subsequent write operations to this stream to occur at end-of- file, as if preceded by an fseek(stream,0,SEEK_END); call. The fdopen function associates a stream with the existing file descriptor, fildes. The mode of the stream (one of the values "r", "r+", "w", "w+", "a", "a+") must be compatible with the mode of the file descriptor. The file position indicator of the new stream is set to that belonging to fildes, and the error and end-of-file indicators are cleared. Modes "w" or "w+" do not cause truncation of the file. The file descriptor is not dup'ed, and will be closed when the stream created by fdopen is closed. The result of applying fdopen to a shared memory object is undefined. The freopen function opens the file whose name is the string pointed to by path and associates the stream pointed to by stream with it. The original stream (if it exists) is closed. The mode argument is used just as in the fopen function. The primary use of the freopen function is to change the file associated with a standard text stream (stderr, stdin, or stdout). RETURN VALUE
Upon successful completion fopen, fdopen and freopen return a FILE pointer. Otherwise, NULL is returned and the global variable errno is set to indicate the error. ERRORS
EINVAL The mode provided to fopen, fdopen, or freopen was invalid. The fopen, fdopen and freopen functions may also fail and set errno for any of the errors specified for the routine malloc(3). The fopen function may also fail and set errno for any of the errors specified for the routine open(2). The fdopen function may also fail and set errno for any of the errors specified for the routine fcntl(2). The freopen function may also fail and set errno for any of the errors specified for the routines open(2), fclose(3) and fflush(3). CONFORMING TO
The fopen and freopen functions conform to ANSI X3.159-1989 (``ANSI C''). The fdopen function conforms to IEEE Std1003.1-1988 (``POSIX.1''). SEE ALSO
open(2), fclose(3), fileno(3) BSD MANPAGE
2002-01-03 FOPEN(3)
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