Tiny Core Linux

Tiny Core Extensions => TCE Talk => Topic started by: Daniel on February 07, 2011, 08:59:49 AM

Title: STDOUT / STDERR
Post by: Daniel on February 07, 2011, 08:59:49 AM

Hi,

With my application, I'am waiting for an USB device.

For that, i do "ls /dev/sdb1"

with my application run under ubuntu 10.04, an error goes to stderr.
with tcl, the error goes to stdout.

I've test : 'ls /dev/sdb2 1>t1 2>t2'
the error result is in t1 (t2 for ubuntu).

what have i to do to change that and to have the same as ubuntu in order to do both without change?

thanks
Daniel.

[EDIT]
or an other way of doing the same in both cases?  :)

Title: Re: STDOUT / STDERR
Post by: danielibarnes on February 07, 2011, 11:54:17 AM

To redirect both stdout and stderr to the same output, use "&>" as in:
ls /dev/sdb1 &>t

However, if you are waiting on a usb device there may be better options depending on your use:

1) During bootup, you can use the waitusb bootcode and include the device, label or UUID of a USB device (if it is always the same):
waitusb=7:DEVICE=/dev/sdb1
waitusb=7:UUID=xxxx
waitusb=7:LABEL="label"

2) Use blkid to check for the presence of the device instead of ls:
blkid -lt DEVICE=/dev/sdb1 && echo Success
or
blkid -lt DEVICE=/dev/sdb1 || echo Failed
or
while ! blkid -lt DEVICE=/dev/sdb1; do sleep 0.25; done

Title: Re: STDOUT / STDERR
Post by: Daniel on February 08, 2011, 08:43:04 AM

Thanks!

Now, i'm using blkid to see if an usb device is present.

blkid -o device
with filtering the response.
:)

Daniel.

PS: there is a difference between tcl and ubuntu.
Perhaps because in tcl, stderr is redirected on stdout ? ??? ??? ???

Title: Re: STDOUT / STDERR
Post by: danielibarnes on February 08, 2011, 10:26:16 AM

Quote

PS: there is a difference between tcl and ubuntu.

It may be the shell. Ash and bash use the syntax I gave you. I realize you may not need it now, but you can also redirect like this:

ls -l /dev/sdb1 2>&1 >t

Title: Re: STDOUT / STDERR
Post by: Daniel on February 09, 2011, 12:00:07 AM

Thanks!

What i wanted is to have the same for both ubuntu and tcl.

error -> stderr.

With "blkid", i modify the program for both!
:)
Daniel.