Dear all,
I wonder what the integer flag 0 and 1 do in the following statements.
readfd=open(FIFO,0);
writefd=open(FIFO2,1);
int open(const char *pathname, int flags, mode_t mode);
Shouldn't the flags argument be arranged in bitwise format?(O_RDONLY | O_WRONLY | O_RDWR )
Shawn
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by: pambooPosted on 2002-12-17 at 19:27:17ID: 7599133
Yeah , u can use bitwise OR operator (|), so that the effect of several flags are combined together
Actually,u have 2 open system calls as follows ,
int open(const char *path, int flags);
int open(const char *path, int flags, mode_t mode);
PARAMETERS
path: [in] the path of the new file to create.
mode: [in] the new permission mask of the file. It is masked by the umask value: (mode & ~umask).
flags:
The flags parameter must be one of the following and u can combine flags using |:
O_RDONLY
the file is opened for reading.
O_WRONLY
the file is opened for writing.
O_RDWR
the file is opened for both reading and writing.
The following values may be or'ed together and with one of the preceding values:
O_CREAT
create the file if it does not exist.
O_EXCL
used with O_CREAT, if the file exists, the call fails. The test for existence and the creation if the file does not exists is atomic operation according to POSIX.1.
O_NOCTTY
the file will not become the controly tty of the task even if the file is a tty and the task does not have a controling terminal.
O_TRUNC
if the file already exists, truncate its lenght to 0.
O_APPEND
the file is opened for appending. The file pointer is always at the end of the file.
O_NONBLOCK or O_NDELAY
the calls manipulating the file never block.
O_SYNC
the file buffers are always synchronized with the on disk file. The write calls block until the data is completely written on disk. This is not POSIX.1.
create creates a new file. The new file is open for writing only. If a file with the same path already existed, then it is trucated.
And I think 1 and 0 u r talking is from the system APIs read and write .... 1 means Inoput device and 0 means outpurt device
For eg:
------
read(1,buf,buflen)
Read from the input buffer and store it in buf array
Okay friend ... See u ... Bye,
With love,
S.Nagarjan.