SOPEN(DOS) XENIX System V SOPEN(DOS)
Name
sopen - Opens a file for shared reading and writing.
Syntax
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <share.h>
#include <io.h>
int sopen (pathname, oflag, shflag[, pmode]);
char *pathname;
int oflag;
int shflag;
int pmode;
Description
The sopen function opens the file specified by pathname and
prepares the file for subsequent shared reading or writing
as defined by oflag and shflag. oflag is an integer
expression formed by combining one or more of the following
manifest constants, defined in fcntl.h. When more than one
manifest constant is given, the constants are joined with
the OR operator (|).
Oflag Meaning
O_APPEND Reposition the file pointer to the
end of the file before every write
operation.
O_CREAT Create and open a new file; this
has no effect if the file specified
by pathname exists.
O_EXCL Return an error value if the file
specified by pathname exists. Only
applies when used with O_CREAT.
O_RDONLY Open file for reading only; if this
flag is given, neither O_RDWR nor
O_WRONLY may be given.
O_RDWR Open file for both reading and
writing; if this flag is given,
neither O_RDONLY nor O_WRONLY may
be given.
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SOPEN(DOS) XENIX System V SOPEN(DOS)
O_TRUNC Open and truncate an existing file
to 0 length; the file must have
write permission, and the contents
of the file are destroyed.
O_WRONLY Open file for writing only; if this
flag is given, neither O_RDONLY nor
O_RDWR may be given.
O_BINARY Open file in binary (untranslated)
mode. (See fopen for a description
of binary mode.)
O_TEXT Open file in text (translated)
mode. (See fopen for a description
of text mode.)
_TRUNC destroys the complete contents of an existing file.
Use with care.
Shflag is a constant expression consisting of one of the
following manifest constants, defined in share.h. See your
MS-DOS documentation for detailed information on sharing
modes.
Shflag Meaning
SH_COMPAT Set compatibility mode.
SH_DENYRW Deny read and write access to file.
SH_DENYWR Deny write access to file.
SH_DENYRD Deny read access to file.
SH_DENYNONE Permit read and write access.
The pmode argument is required only when _CREAT is
specified. If the file does not exist, pmode specifies the
file's permission settings, which are set when the new file
is closed for the first time. Otherwise, the pmode argument
is ignored. The pmode argument is an integer expression
containing one or both of the manifest constants S_IWRITE
and S_IREAD, defined in sys/stat.h. When both constants are
given, they are joined with the OR operator (|). The
meaning of the pmode argument is as follows:
Value Meaning
S_IWRITE Writing permitted
S_IREAD Reading permitted
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SOPEN(DOS) XENIX System V SOPEN(DOS)
S_IREAD | S_IWRITE Reading and writing permitted
If write permission is not given, the file is read-only.
Under MS-DOS all files are readable; it is not possible to
give write-only permission. Thus, the modes S_IWRITE and
S_IREAD | S_IWRITE are equivalent.
sopen applies the current file permission mask to pmode
before setting the permissions (see umask).
Return Value
sopen returns a file handle for the opened file. A return
value of -1 indicates an error, and errno is set to one of
the following values:
Value Meaning
EACCES Given pathname is a directory; or
the file is read-only but an open
for writing was attempted; or a
sharing violation occurred (the
file's sharing mode does not allow
the specified operations; MS-DOS
versions 3.0 or later only).
EEXIST The _CREAT and _EXCL flags are
specified but the named file
already exists.
EINVAL SHARE.COM not installed.
EMFILE No more file handles available (too
many open files).
ENOENT File or pathname not found.
See Also
close(S), creat(S), fopen(S), open(S), umask(S)
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SOPEN(DOS) XENIX System V SOPEN(DOS)
Example
#include <fcntl.h> #include <sys/types.h> #include
<sys/stat.h> #include <share.h> #include <io.h>
extern unsigned char _osmajor; int fh;
/* The _osmajor variable is used to test
** the MS-DOS version number before
** calling sopen. */
if (_osmajor >= 3) fh = sopen ("data", O_RDWR |
O_BINARY, SH_DENYRW); else fh = open ("data",
O_RDWR | O_BINARY);
Notes
The sopen function should be used only under MS-DOS version
3.0 or later. Under earlier versions of MS-DOS, the shflag
argument is ignored.
File sharing modes will not work correctly for buffered
files, so do not use fdopen to associate a file opened for
sharing (or locking) with a stream.
This call must be compiled with the -dos flag.
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