problem closing stdout - VxWorks

Hi EveryOne:
I am New to vxworks.I am trying to get the
list of files in the directories using ls() and i want to redirect
ls() > to a pipe so i am closing the stdout file descriptor and
duplicating pipe fileDescriptor.But the pbm im facing is when
execution comes to line close(1) my simulator gets hanged.

I m working in workBench 2.5 .

Can anyone give me some suggestions.

On Aug 14, 5:09 pm, senthil wrote:
> Hi EveryOne:
> I am New to vxworks.I am trying to get the
> list of files in the directories using ls() and i want to redirect
> ls() > to a pipe so i am closing the stdout file descriptor and
> duplicating pipe fileDescriptor.But the pbm im facing is when
> execution comes to line close(1) my simulator gets hanged.
>
> I m working in workBench 2.5 .
>
> Can anyone give me some suggestions.

In VxWorks the File descriptors are shared and accessible across
tasks. So, it is quite possible that the FD stdout that was closed was
being used by some other task.

In general, closing the stdin, stdout and stderr is not recommended.

Now, coming to redirection of the output - there are specific APIs
that would help you achieve this -

1) iosTaskStdSet( ) - set the file descriptor for task standard input/
output/error

void ioTaskStdSet
(
int taskId, /* task whose std fd is to be set (0 = self) */
int stdFd, /* std input (0), output (1), or error (2) */
int newFd /* new underlying file descriptor */
)

2) ioGlobalStdSet( ) - set the file descriptor for global standard
input/output/error

int ioGlobalStdGet
(
int stdFd /* std input (0), output (1), or error (2) */
)

Hope this would help you!

Regards,
Sriram.

Thanx for ur suggestions.
I tried it now i am able to redirect stdout to pipe.
is there any way after doing some process (in same Task) can i get
back the redirected file descriptor to standard output.

On Aug 16, 9:47 am, senthil wrote:
> Thanx for ur suggestions.

Well, sorry, I was slightly wrong with the API descriptions earlier.
Please find them corrected below -

The two APIs related to redirecting the standard input, output and
error are as below -

1) ioTaskStdSet( ) - set the file descriptor for task standard input/
output/error

void ioTaskStdSet
(
int taskId, /* task whose std fd is to be set (0 = self) */
int stdFd, /* std input (0), output (1), or error (2) */
int newFd /* new underlying file descriptor */
)

2) ioGlobalStdSet( ) - set the file descriptor for global standard
input/output/error

void ioGlobalStdSet
(
int stdFd, /* std input (0), output (1), or error (2) */
int newFd /* new underlying file descriptor */
)

> I tried it now i am able to redirect stdout to pipe.

I assume that you had used the correct form of the API while you were
able to successfully redirect the stdout to pipe.

> is there any way after doing some process (in same Task) can i get
> back the redirected file descriptor to standard output.

Yes, you can retrieve and store the current file descriptor that
denotes the stdout before redirection. Once you are done with the
needed processing, you can set back the stdout to the file descriptor
that you had stored earlier.

The current file descriptor that denote the stdout can be obtained by
using the following APIs -

1) ioTaskStdGet( ) - get the file descriptor for task standard input/
output/error

int ioTaskStdGet
(
int taskId, /* ID of desired task (0 = self) */
int stdFd /* std input (0), output (1), or error (2) */
)

2) ioGlobalStdGet( ) - get the file descriptor for global standard
input/output/error

int ioGlobalStdGet
(
int stdFd /* std input (0), output (1), or error (2) */
)

Let us consider an example below -

int pipeFd = 10;
int prevStdOut = ioTaskStdGet(0, 1); /* Retrieve and store (backup)
the current stdout file descriptor */

if(prevStdOut != ERROR) {
ioTaskStdSet(0, 1, pipeFd); /* Redirect the stdout to the pipe
device */

....
.... /* Do some processing */
....

ioTaskStdSet(0, 1, prevStdOut); /* Restore the stdout to what it was
earlier */
}


Hope this answered your query!

Regards,
Sriram.

Hai
Thanx for ur suggestions.
I tried it now i am able to get back STDOUT back to my task.