11-06-2002
umask
in this unix book that i have, it says:
the statement:
filedes = open(pathname, O_CREAT, mode);
is actually
filedes = open(pathname, O_CREAT, (~mask)&mode); /* ~ is the negation symbol */
like it's doing some type of masking.
for example,
fd = open("newfile", O_CREAT, 0644);
will actually given the mode of 0640.
how did it come up with that? what value does it mask to my mode set to come up with 0640?
why is it doing that?
thanks
Last edited by bb00y; 11-06-2002 at 04:51 AM..
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DIO_OPEN(3) 1 DIO_OPEN(3)
dio_open - Opens a file (creating it if necessary) at a lower level than the C library input/ouput stream functions allow.
SYNOPSIS
resource dio_open (string $filename, int $flags, [int $mode])
DESCRIPTION
dio_open(3) opens a file and returns a new file descriptor for it.
PARAMETERS
o $filename
- The pathname of the file to open.
o $flags
- The $flags parameter is a bitwise-ORed value comprising flags from the following list. This value must include one of O_RDONLY,
O_WRONLY, or O_RDWR. Additionally, it may include any combination of the other flags from this list.
o O_RDONLY - opens the file for read access.
o O_WRONLY - opens the file for write access.
o O_RDWR - opens the file for both reading and writing.
o O_CREAT - creates the file, if it doesn't already exist.
o O_EXCL - if both O_CREAT and O_EXCL are set and the file already exists, dio_open(3) will fail.
o O_TRUNC - if the file exists and is opened for write access, the file will be truncated to zero length.
o O_APPEND - write operations write data at the end of the file.
o O_NONBLOCK - sets non blocking mode.
o O_NOCTTY - prevent the OS from assigning the opened file as the process's controlling terminal when opening a TTY device
file.
o $mode
- If $flags contains O_CREAT, $mode will set the permissions of the file (creation permissions). $mode is required for correct
operation when O_CREAT is specified in $flags and is ignored otherwise. The actual permissions assigned to the created file will
be affected by the process's umask setting as per usual.
RETURN VALUES
A file descriptor or FALSE on error.
EXAMPLES
Example #1
Opening a file descriptor
<?php
$fd = dio_open('/dev/ttyS0', O_RDWR | O_NOCTTY | O_NONBLOCK);
dio_close($fd);
?>
SEE ALSO
dio_close(3).
PHP Documentation Group DIO_OPEN(3)