Synopsis
Close an open file descriptor
Usage
Int_Type close (FD_Type fd)
Description
The
close function is used to open file descriptor of type
FD_Type . Upon success 0 is returned, otherwise the function
returns \-1 and sets
errno accordingly.
See also
Synopsis
Convert a stdio File_Type object to a FD_Type descriptor
Usage
FD_Type fileno (File_Type fp)
Description
The fileno function returns the FD_Type descriptor
associated with the File_Type file pointer. Upon failure,
\NULL is returned.
See also
Synopsis
Determine if an open file descriptor refers to a terminal
Usage
Int_Type isatty (FD_Type or File_Type fd)
Description
This function returns 1 if the file descriptor fd refers to a
terminal; otherwise it returns 0. The object fd may either
be a File_Type stdio descriptor or an FD_Type object.
See also
Synopsis
Reposition a file descriptor's file pointer
Usage
Long_Type lseek (FD_Type fd, Long_Type ofs, int mode)
The lseek function repositions the file pointer associated
with the open file descriptor fp to offset ofs
according to the mode parameter. Specifically, mode must be
one of the values:
SEEK_SET Set the offset to ofs
SEEK_CUR Add ofs to the current offset
SEEK_END Add ofs to the current file size
Upon error, lseek returns \-1 and sets errno . If
successful, it returns the new filepointer offset.
Notes
Not all file descriptors are capable of supporting the seek
operation, e.g., a descriptor associated with a pipe.
By using SEEK_END with a positive value of the ofs
parameter, it is possible to position the file pointer beyond the
current size of the file.
See also
function open
Synopsis
Open a file
Usage
FD_Type open (String_Type filename, Int_Type flags [,Int_Type mode])
Description
The
open function attempts to open a file specified by the
filename parameter according to the
flags parameter,
which must be one of the following values:
O_RDONLY (read-only)
O_WRONLY (write-only)
O_RDWR (read/write)
In addition,
flags may also be bitwise-or'd with any of the
following:
O_BINARY (open the file in binary mode)
O_TEXT (open the file in text mode)
O_CREAT (create file if it does not exists)
O_EXCL (fail if the file already exists)
O_NOCTTY (do not make the device the controlling terminal)
O_TRUNC (truncate the file if it exists)
O_APPEND (open the file in append mode)
O_NONBLOCK (open the file in non-blocking mode)
If
O_CREAT is used for the
flags parameterm then the
mode parameter must be present.
mode specifies the
permissions to use if a new file is created. The actual file
permissions will be affected by the process's
umask via
mode&~umask . The
mode parameter's value is
constructed via bitwise-or of the following values:
S_IRWXU (Owner has read/write/execute permission)
S_IRUSR (Owner has read permission)
S_IWUSR (Owner has write permission)
S_IXUSR (Owner has execute permission)
S_IRWXG (Group has read/write/execute permission)
S_IRGRP (Group has read permission)
S_IWGRP (Group has write permission)
S_IXGRP (Group has execute permission)
S_IRWXO (Others have read/write/execute permission)
S_IROTH (Others have read permission)
S_IWOTH (Others have write permission)
S_IXOTH (Others have execute permission)
Upon success
open returns a file descriptor object
(
FD_Type ), otherwise
NULL is returned and
errno
is set.
Notes
If you are not familiar with the
open system call, then it
is recommended that you use
fopen instead.
See also
function read
Synopsis
Read from an open file descriptor
Usage
UInt_Type read (FD_Type fd, Ref_Type buf, UInt_Type num)
Description
The
read function attempts to read at most
num bytes
into the variable indicated by
buf from the open file
descriptor
fd . It returns the number of bytes read, or \-1
and sets
errno upon failure. The number of bytes read may be
less than
num , and will be zero if an attempt is made to read
past the end of the file.
Notes
read is a low-level function and may return \-1 for a variety
of reasons. For example, if non-blocking I/O has been specified for
the open file descriptor and no data is available for reading then
the function will return \-1 and set
errno to
EAGAIN .
See also
Synopsis
Write to an open file descriptor
Usage
UInt_Type write (FD_Type fd, BString_Type buf
Description
The
write function attempts to write the bytes specified by
the
buf parameter to the open file descriptor
fd . It
returns the number of bytes successfully written, or \-1 and sets
errno upon failure. The number of bytes written may be less
than
length(buf) .
See also