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Full Discussion: Eval set -- and more
Top Forums UNIX for Beginners Questions & Answers Eval set -- and more Post 302990823 by Corona688 on Wednesday 1st of February 2017 10:26:12 AM
Old 02-01-2017
-- "$@" just means, "take the following arguments literally" and "all the following arguments, properly separated and quoted". If your arguments are "a b" "c d" "e f", "$@" will put them in as "a b" "c d" "e f", not "a" "b" "c" "d" "e" "f".

The 'shift' eats a commandline argument, i.e. converts $1=a, $2=b, $3=c, $4=d into $1=b, $2=c, $3=d. shift 2 moves it all the way to $1=c, $2=d. It's done since that particular branch uses an argument, so it has to remove two things from the list (the -r and the argument following it) not just one.

I have no idea why they're doing 'eval set', only theories. That's dangerous and dumb. They may be trying to process quotes inside quotes.



They are getting the values from 'getopt', the standard way to handle commandline arguments. I can't really explain its workings, but I'm sure others can.
Last edited by Corona688; 02-01-2017 at 11:48 AM..
 

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LEARN ABOUT DEBIAN

adplugdb

ADPLUGDB(1)							   User Commands						       ADPLUGDB(1)

NAME

       adplugdb - AdPlug database maintenance utility

SYNOPSIS

       adplugdb [OPTION]... COMMAND [ARGUMENT]...

DESCRIPTION

       adplugdb  maintains database files in AdPlug database format. It can add, list and remove records within a central database, or merge a set
       of databases together into one single database.

       adplugdb always operates on a central database file. The location of this database file is determined by first checking if the user  has  a
       home  directory.  If  a	home  directory  is  present, the database file will be located in ~/.adplug/adplug.db. If a home directory is not
       present, a database file adplug.db will be looked for in the current working directory.

       A system-wide database file can be used instead, by specifying the -s commandline option. The  system-wide  database  file  is  located	in
       /usr/com/adplug/adplug.db and may only be manipulated as the superuser. An arbitrary database file might be used as well, by specifying the
       -d commandline parameter. Only one database file may be manipulated at a time.

EXIT STATUS

       adplugdb returns with a successful exit status (0 on most systems) on successful operation. An unsuccessful exit status (1 on most systems)
       is returned otherwise.

COMMANDS

       Commands control the main operation mode of adplugdb. Commands can have a number of arguments. Only one command may be specified at a time.

       add    This  command takes a list of filenames, separated by spaces, as arguments. Each file is examined and a record is added to the data-
	      base if the file is supported by AdPlug. By default, the record will be of type Plain, unless the -t commandline option is specified
	      (see  below).  The  default  comment  entry is the specified filename. If a record for a file is already in the database, it will be
	      replaced by the new record.

       list   This command takes an optional list of filenames or keys, separated by spaces, as arguments. Each file is examined  and  the  corre-
	      sponding	record	is  looked  up from the database and displayed on stdout, in a human-readable form. If no arguments are given, all
	      records from the database are displayed.

       remove This command takes a list of filenames or keys, separated by spaces, as arguments. Each  file  is  examined  and	the  corresponding
	      record is removed from the database.

       merge  This  command  takes  a list of database filenames, separated by spaces, as arguments. Each database file is loaded and the contents
	      are merged and written to the central database file. The database files are processed in the order they are specified on the comman-
	      dline.  Records  from  databases	that were specified earlier take precedence over records from databases that were specified later.
	      Records from the central database take precedence over all other records. This means that only additional  records  from	the  other
	      databases  will  be  added to the central database and if a record is found that is not already in the central database, the version
	      from the earliest specified database that contains this record will be taken. In no way will records ever be overwritten in the cen-
	      tral database.

OPTIONS

       The order of the option commandline parameters is not important.

   Database options:
       -d <file>
	      Specify an arbitrary file to use as the central database.

       -s     Use  the	system-wide  database  file as the central database. This option is only present if adplugdb was compiled with system-wide
	      database file support.

       -t <type>
	      Specify a record type to be used as the type for all newly added records. Each record needs a special type to be useful to  AdPlug's
	      players. The commandline help, displayed using the -h commandline option, presents a list of types that may be specified.

       -c     Prompt for record comment. If this option is given, the user will be prompted and asked for each newly added record's comment.

       -k     Specify  keys  instead  of  filenames. If this option is given, all command arguments that normally are filenames are expected to be
	      record keys instead. Each record in the database has a unique identifying key, generated from the corresponding file's contents.	To
	      manipulate  a  record  entry,  you either must have the exact same file and specify its name, or you specify the record's key, using
	      this option. Keys are specified the same way they are displayed using the list command, as CRC16:CRC32 value in hexadecimal format.

   Generic options:
       -q, --quiet
	      Be more quiet.

       -v, --verbose
	      Be more verbose.

       -h, --help
	      Show summary of commandline commands, arguments and options.

       -V, --version
	      Show version and author information of the program.

AUTHOR

       Simon Peter <dn.tlp@gmx.net>

AdPlug database maintenance utility 2.2.1			   March 4, 2006						       ADPLUGDB(1)
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