Script to scan the disks and make file system Post: 303005653

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Top Forums Shell Programming and Scripting Script to scan the disks and make file system Post 303005653 by Don Cragun on Friday 20th of October 2017 04:35:52 PM

10-20-2017

Registered User

Quote:

Originally Posted by James0806

what is the difference between using

Code:

ls /sys/class/scsi_device/ | while read i; do echo "- - -" > /sys/class/scsi_device/$i/device/rescan;done

and

Code:

for i in /sys/class/scsi_device/*
do
  # must be a directory
  [ -d "$i" ] &&  echo "- - -" > "$i/device/rescan"
done

At first glance, it appears that as long as all files in the directory /sys/class/scsi_device are directories, they should produce similar results. If a file in that directory is not a directory, the 1st script will get an error trying to write to an invalid pathname while the 2nd script will silently ignore any files that are not directories.

In both cases, the scripts make the assumption that every directory in that directory has a subdirectory named device and that the user running the script has permission to create or overwrite a file named rescan in that subdirectory.

In the 2nd script, the shell reads the directory to get the list of files to process and then processes the files found in that list. In the 1st script, ls must be invoked to get the list of files but ls and the rest of the script can run in parallel.

As MadeInGermany said, neither of these demonstrate what would be called production code.

Don Cragun

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LEARN ABOUT FREEBSD

dh_installdebconf

DH_INSTALLDEBCONF(1)						     Debhelper						      DH_INSTALLDEBCONF(1)

NAME

       dh_installdebconf - install files used by debconf in package build directories

SYNOPSIS

       dh_installdebconf [debhelperoptions] [-n] [--params]

DESCRIPTION

       dh_installdebconf is a debhelper program that is responsible for installing files used by debconf into package build directories.

       It also automatically generates the postrm commands needed to interface with debconf. The commands are added to the maintainer scripts by
       dh_installdeb. See dh_installdeb(1) for an explanation of how that works.

       Note that if you use debconf, your package probably needs to depend on it (it will be added to ${misc:Depends} by this program).

       Note that for your config script to be called by dpkg, your postinst needs to source debconf's confmodule. dh_installdebconf does not
       install this statement into the postinst automatically as it is too hard to do it right.

FILES

       debian/package.config
	   This is the debconf config script, and is installed into the DEBIAN directory in the package build directory.

	   Inside the script, the token #DEBHELPER# is replaced with shell script snippets generated by other debhelper commands.

       debian/package.templates
	   This is the debconf templates file, and is installed into the DEBIAN directory in the package build directory.

       debian/po/
	   If this directory is present, this program will automatically use po2debconf(1) to generate merged templates files that include the
	   translations from there.

	   For this to work, your package should build-depend on po-debconf.

OPTIONS

       -n, --no-scripts
	   Do not modify postrm script.

       -- params
	   Pass the params to po2debconf.

SEE ALSO

       debhelper(7)

       This program is a part of debhelper.

AUTHOR

       Joey Hess <joeyh@debian.org>

11.1.6ubuntu2							    2018-05-10						      DH_INSTALLDEBCONF(1)