01-20-2009
Execute while loop
Hi,
I have a background process running for which I want to know the status continuously.
I want to execute a WHILE loop in the command prompt so that it keeps on displaying in the screen.But, I am getting the following errors :-
hyper20:~ 3> while [1]
while?
while?
hyper20:~ 4> while {1}
while?
while?
hyper20:~ 5> while [ 1 ]
while: Expression Syntax.
Could someone please help me in this ?
Thanks.
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LEARN ABOUT REDHAT
losetup
LOSETUP(8) MAINTENANCE COMMANDS LOSETUP(8)
NAME
losetup - set up and control loop devices
SYNOPSIS
losetup [ -e encryption ] [ -o offset ] loop_device file
losetup [ -d ] loop_device
DESCRIPTION
losetup is used to associate loop devices with regular files or block devices, to detach loop devices and to query the status of a loop
device. If only the loop_device argument is given, the status of the corresponding loop device is shown.
OPTIONS
-d detach the file or device associated with the specified loop device.
-e encryption
enable data encryption. The following keywords are recognized:
NONE use no encryption (default).
XOR use a simple XOR encryption.
DES use DES encryption. DES encryption is only available if the optional DES package has been added to the kernel. DES encryption
uses an additional start value that is used to protect passwords against dictionary attacks.
-o offset
the data start is moved offset bytes into the specified file or device.
RETURN VALUE
losetup returns 0 on success, nonzero on failure. When losetup displays the status of a loop device, it returns 1 if the device is not con-
figured and 2 if an error occurred which prevented losetup from determining the status of the device.
FILES
/dev/loop0,/dev/loop1,... loop devices (major=7)
EXAMPLE
If you are using the loadable module you must have the module loaded first with the command
# insmod loop.o
The following commands can be used as an example of using the loop device.
dd if=/dev/zero of=/file bs=1k count=100
losetup -e des /dev/loop0 /file
Password:
Init (up to 16 hex digits):
mkfs -t ext2 /dev/loop0 100
mount -t ext2 /dev/loop0 /mnt
...
umount /dev/loop0
losetup -d /dev/loop0
If you are using the loadable module you may remove the module with the command
# rmmod loop
RESTRICTION
DES encryption is painfully slow. On the other hand, XOR is terribly weak.
AUTHORS
Original version: Theodore Ts'o <tytso@athena.mit.edu>
Original DES by: Eric Young <eay@psych.psy.uq.oz.au>
Linux Nov 24 1993 LOSETUP(8)