fd_open


`fd_open`
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`fd_open`

fd_open — opens a file or device and assigns it a file descriptor.

Synopsis

fd_open (name, mode)

Arguments

name: The name of a file, as a string.
mode: The mode for opening the file.

Returns

A non-negative integer representing the lowest numbered unused file descriptor if successful. If an error occurs, the function returns -1 and sets the errno.

Description

This function opens a file for reading and/or writing, and assigns it a file descriptor which is used as an argument by other functions such as fd_read and fd_write. The file that is opened could be a regular file, a directory, or a block or character device. Legal mode values are:

O_RDONLY Read-only mode
O_WRONLY Write-only mode
O_RDWR Read-Write mode

Any combination of the following flags may be bitwise OR-ed with the open mode to modify how the file is accessed:

O_APPEND Append (writes guaranteed at the end)
O_CREAT Opens with file create
O_EXCL Exclusive open
O_NOCTTY Don't assign a controlling terminal
O_NONBLOCK Non-blocking I/O
O_TRUNC Open with truncation
O_DSYNC Data integrity synch
O_SYNC File integrity synch
O_TEMP Temporary file, don't put to disk
O_CACHE Cache sequential files too

If an error occurs -1 is returned and errno is set to one of the following:

EACCES Search permission denied on a portion of the path prefix, or the file exists and the permissions required to open the file in the given mode so not exist.
EBADFSYS The file or the path prefix to the file was found to be corrupted
EBUSY The file is already open for writing.
EEXIST O_CREAT and O_EXCL are set and the named file exists
EINTR The function was interrupted by a signal
EISDIR The named file is a directory
EMFILE Too many file descriptors are currently in use by this process
ENAMETOOLONG The length of the path to the file is too long.
ENFILE Too many files are currently open on the system
ENOENT O_CREAT is not set and the file does not exist
ENOSPC The directory or file system which would create the new file cannot be extended
ENOTDIR A component of the path to the file is not a directory
ENXIO O_NONBLOCK is set, the file is a FIFO, O_WRONLY is set, and no process has the file open for reading
EROFS The named file resides on a read-only file system.

Example

Gamma> require_lisp("const/filesys");
"/usr/cogent/lib/const/filesys.lsp"
Gamma> ptr = fd_open("/fd/ttyp8",O_WRONLY);
4
Gamma> fd_write(ptr,"\nhello\n");
7