open - open for reading or writing

NAME

SYNOPSIS

#include <stdio_p.h> #include <fcntl_p.h>

FD open(path, oflag[, mode]) char *path; int oflag, mode;

DESCRIPTION

path points to a path name naming a file on either the satellite system or the host system (host path names are preceded with a '!'). Some path names are reserved to open the local device drivers on the satellite. A list of possible reserved names (depending on how the satellite is configured) includes:

/dev/tty: serial lines
/dev/ck: programmable clock
/dev/adc: analog to digital converter
/dev/dac: digital to analog converter
/dev/pk: packet driver
/dev/sm: smpte time code
/dev/rl: RL02 disk
/dev/vd: visual display
/dev/dk: display clock
/dev/hco: high current digital output
/dev/ttl: digit input and output
/dev/ib: 16-bit input buffer

See section 4 for a description of the function of these special files.

open opens a file descriptor for the named file and sets the file status flags according to the value of oflag. oflag values are constructed by ORing flags from the following list:

Choose 1 from the next 3 permission flags.

O_RDONLY

Open for reading only.

O_WRONLY

Open for writing only.

O_RDRW

Open for reading and writing.

O_APPEND

If set, the file pointer will be set to the end of the file before the first write.

O_CREAT

If the file exists, this flag has no effect. If path refers to a host file, this file's owner ID is set to the process's effective user ID, the file's group ID is set to the process's effective group ID, and the low-order 12 bits of the file mode are set to the value of mode modified by ORing together some combination of the following:

04000 set user ID on execution
02000 set groupo ID on execution
01000 save text image after execution
00400 read by owner
00200 write by owner
00100 execute (search on directory) by owner
00070 read, write, execute (search) by group
00007 read, write, execute (search) by others

If path refers to a satellite file, only the read/write/execute by owner fields of mode are used.

O_TRUNC

If the file exists, its length is truncated to 0 and the mode and owner are unchanged.

O_EXCL

If O_EXCL and O_CREAT are set, open will faile if the file exists.

Upon successful completions a non-negative integer, the file descriptor, is returned.

The file pointer used to mark the current position within the file is set to the beginning of the file, unless O_APPEND is set, in which case the file pointer is set to the end of the file.

No process may have more than 20 host files or 10 satellite files open simultaneously. Any number of special satellite devices may be open at once.

The named file is opened unless one or more of the following are true:

A component of the path prefix is not a directory. [ENOTDIR]
O_CREAT is not set and the named files does not exist. [ENOENT]
A component of the path prefix denies search permission. [EACCES]
oflag permission is denied for the named file. [EACCES]
The named file is a directory and oflag is write or read/write. [EISDIR]
The maximum file descriptors are currently open. [ENFILE]
The named file is a character special or block special file, and
the device associated with this special file does not exist. [ENXIO]
O_CREAT and O_EXCL are set, and the named file exists. [EEXIST]

RETURN VALUE

Upon successful completion, a non-negative integer, namely a file descriptor, is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

SEE ALSO