Self deleting script Post: 88031

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Top Forums Shell Programming and Scripting Self deleting script Post 88031 by Perderabo on Monday 31st of October 2005 09:25:43 AM

10-31-2005

Administrator Emeritus

Quote:

Originally Posted by Unbeliever

Because the interpreter (the shell) loads the whole script and then executes it line by line. It would be really rather ineficient for it to repeatedly read a line and execute that line.

Ordinary shells behave like that, but ksh is much more efficient. To execute a loop, it ensures that it has the entire loop in core, then it compiles the loop and then it executes the compiled code. Other shells need to re-interpret the code on each iteration. This the secret of ksh's speed.

More than that, despite the name, rm does not remove files, it unlinks them from directories. If the file has zero links and is not open by any process, it is removed. So the file will not disappear while ksh has it open. Instead, it becomes a file with zero file names. This behavior is a good way to handle temporary files and a lot of programs do that... create a file, unlink it, then use it. It is guaranteed to disappear upon program exit.

Newbie admins post fairly often saying that a big file ate their filesystem, they deleted it, and they did not get the space back. This is why that happens. The file is still consuming space and will until the process that has it opened is killed. And now the file has no name so it is much harder to deal with.

Perderabo

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LEARN ABOUT OSF1

uudemon.cleanu

uudemon(4)						     Kernel Interfaces Manual							uudemon(4)

NAME

       uudemon.admin,  uudemon.cleanu,	uudemon.hour,  uudemon.poll  -	Administrative shell scripts for polling remote systems, cleaning up spool
       directories, reporting status to the system administrator, and routine invocations of the uuxqt and uusched daemons

SYNOPSIS

       These shell scripts reside in the following directory:
	  /usr/lib/uucp

DESCRIPTION

       All the scripts can be run from the command line or can be run automatically by the cron daemon. To automatically run the  scripts,  remove
       the comment character (#) from the beginning of the relevant line in the /var/spool/cron/crontabs/uucp file.

       This  script  reports  status  to  the system administrator. It issues the uustat command to find out the status of uucp jobs. It mails the
       results to the uucp login ID. The script may be modified to send mail to any login ID such as the uucp administrative login ID  (uucpa)	or
       root.  This script cleans up the /var/spool/uucp and /var/spool/uucppublic directories by running the uucleanup command. The uucleanup com-
       mand is run with the following parameters: -C7, -D7, X2, -o2, -W1.  This script runs the uusched and uuxqt daemons in the background.  This
       script  polls  the  systems  listed  in	the  /usr/lib/uucp/Poll file.  The uudemon.poll script should be scheduled before the uudemon.hour
       script. This allows uudemon.poll to create any command files before cron runs the uudemon.hour script.

FILES

       Contains the uudemon.admin, uudemon.cleanu, uudemon.hour and uudemon.poll files.  Contains the uucp file.

RELATED INFORMATION

       Commands: cron(8), uucleanup(8), uusched(8), uuxqt(1)

       Files: /usr/lib/uucp delim off

																	uudemon(4)