Advanced Oracle Utilities: The Definitive Reference by Rampant
TechPress is written by top Oracle database experts (Bert Scalzo, Donald Burleson, and Steve Callan). The following
is an excerpt from the book.
To redirect program output, UNIX provides the << and >> commands.
This is very useful when the Oracle DBA wants to keep logs in the
UNIX environment. A typical
usage might be to write a notation to the Oracle alert log that the file
has been checked for errors.
The command below could be used for this purpose:
echo '*****Alert log checked at
2/5/2002
by Andrew Kerber ****' >> \
$DBA/$ORACLE_SID/bdump/alert_$ORACLE_SID.log
The >> command can also be used to append to an existing file of errors.
A common application is to keep a running list of all Oracle
trace file names. The
following command can be used to write all new trace file names into a
list. Note that the first command line uses a single ">" to recreate the
trace_file_names.lst file, while subsequent redirects use the ">>"
directive to append new entries to this file.
ls –al $DBA/$ORACLE_SID/bdump/*.trc
> /tmp/trace_file_names.lst
ls –al $DBA/$ORACLE_SID/udump/*.trc
>> /tmp/trace_file_names.lst
ls –al $DBA/$ORACLE_SID/cdump/*.trc
>> /tmp/trace_file_names.lst
Next, it may be necessary to suppress UNIX command
output.
Redirecting Output to a NULL Device
If one does not wish to see the output of a UNIX command (typically a
batch job), use the /dev/null device to suppress the output. The
/dev/null device is the equivalent of the DD DUMMY syntax in the Cobol.
The /dev/null device is often used in scheduled tasks (using the
UNIX crontab utility) if the output from the command is not required. In
the next example, submit a large batch job and suppress the output.
The ampersand causes UNIX to run the job in the background (detached
from the starting process), and the "2>&1" syntax tells UNIX to redirect
the standard error output to standard output.
In this example, all possible output from large_file.exe will be
suppressed:
./large_job.exe & 2>&1 > /dev/null
The tee command can be used
to redirect multiple output streams.
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