Unfamiliar array syntax Post: 302453873

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Top Forums Shell Programming and Scripting Unfamiliar array syntax Post 302453873 by thumper on Thursday 16th of September 2010 04:18:52 PM

09-16-2010

Registered User

Unfamiliar array syntax

I recently was handed responsibility for a script which has array references that are new to me and I could use some help understanding them.

Parts of the config file and script are included. This script collects backups from a jail server of the jails running on that host. Several jail servers are backed up.

In the first config file the collect0_backup_host="host.xxx.net" refers to the jail host.
It is the syntax of collect0_backup_host that throws me. collect0 is translated to
$collect${N} in the script -- this part I understand -- but the _backup-host (variable?)
that is appended to collect0 is confusing me. I've never seen an array defined this way before and could use some useful links or explaination of how this works.

Thanks
thumper

Code:

config file

collect0_backup_host="host.xxx.net"
collect0_jails="host9.xxx.net host1.xxx.net host2.xxx.net host4.xxx.net"
collect0_backups_dir="/backups/"
collect0_remote_user="host_backups"
collect0_private_key_file="/etc/ssh/jail_backups/host_backups"
#
collect1_backup_host="alt-host.xxx.net"
collect1_jails="dumbo.xxx.net mickey.xxx.net"
collect1_backups_dir="/backups/"
collect1_remote_user="snark_backups"
collect1_private_key_file="/etc/ssh/jail_backups/snark_backups"
#



script


backup_host=`eval echo \\$collect${N}_backup_host`


while backup_host do
  do-something
done


jails=`eval echo \\$collect${N}_jails`

    remote_user=`eval echo \\$collect${N}_remote_user`
    if [ ! ${remote_user} ]; then
        echo
        echo "ERROR: no remote user defined for collecting backups from ${backup_host}"
        echo
        ERROR_JAILS="${ERROR_JAILS} ${jails}"



        # iterate to the set of jail variables
        N=$(expr ${N} + 1)
        backup_host=`eval echo \\$collect${N}_backup_host`

        continue

Last edited by Scott; 09-16-2010 at 05:20 PM.. Reason: Replaced ICODE tags with CODE tags

thumper

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LEARN ABOUT DEBIAN

alsearch

ALSEARCH(1)						User Contributed Perl Documentation					       ALSEARCH(1)

NAME

       alsearch - Search the AudioLink database for music

SYNOPSIS

       alsearch [OPTION]... search_option... --td=/some/path/to/create/links/

       alsearch [OPTION]... search_option... -s

DESCRIPTION

       You can use this script to search for songs in the AudioLink database. You can specify one or several options for the artist, composer,
       lyricist, album, etc., as the search criteria.

       You can specify several search_option options to search for particular music files. See the section on "search options" for the list of
       options.

       The search is not case sensitive. alsearch looks for strings as well as sub-strings in the fields being searched. See the "examples"
       section for more information.

       Specifying the --td (target directory) option is mandatory for creating links to the actual files. This directory will contain the symbolic
       links to the actual audio files. The directory will be created if it doesn't exist.

       Creating symbolic links to the actual files is analogous to creating playlists in audio-playing software. Symbolic links are actually just
       point to the actual files on the hard disk. This way of creating and storing playlists is very useful in several ways, some of which are:

       1. Compatible across various audio players
	   Since the "playlists" are actually files represented on your hard disk, you can add whole directories generated by the alsearch program
	   in the playlist of your audio software. If you switch to another music player for whatever reason, you still have your playlists. You
	   don't have to bother about compatibility between the playlist formats of the two players.

       2. Can be seen and operated upon in a file browser
	   As the symbolic links are present on a file-system, your playlist collection can be viewed by using normal file operations in the shell
	   or using a GUI-based file browsing program. If the file browsing program is supports file traversals and symlinks, it'll show you the
	   information of the actual song.

OPTIONS

       --help
	   Brief usage information

       --host=xxx
	   Connects to the MySQL server on the target host. Default is localhost.

       --pass=xxx
	   Password for the database

       -s, --na
	   Just displays the search results, doesn't create links (simulation mode)

       --td=xxx
	   Target-directory in which to create links

       --user=xxx
	   Username for the database

       -v, --verbose
	   Displays some extra information. Useful for spotting errors and sending debug information.

SEARCH OPTIONS

       --album=xxx
	   Search in the "album" field

       --artist=xxx
	   Search in the artist/band/performers fields. You can give this option multiple times, for example:

	   "alsearch --artist=kishore --artist=asha --td=/songs/asha_kishore"

       --comment=xxx
	   Search in the "comment" field

       -c, --composer=xxx
	   Search in the "composer" field

       --genre=xxx
	   Search in the "genre" field

       -l, --lyricist=xxx
	   Search in the "lyricist" field

       --title=xxx
	   Search in the "title" field

EXAMPLES

       The options that take arguments can be specified in two ways:

       "alsearch --artist="kishore kumar" --td=/songs/kishore"

       "alsearch --artist "kishore kumar" --td /songs/kishore"

       That is, the option and the argument can be separated with a ' ' (space) or an '=' (equal) sign.

       In case you want to search for a string that has spaces, enclose the string in " ".

       "alsearch --artist=kishore --composer=burman --lyricist=bakshi"

       Will search for songs sung by *Kishore*, composed by *Burman* and written by *Bakshi*. Any name in the composer field which have "burman"
       in them will be matched. This means, it'll find songs composed by RD Burman, SD Burman, etc. This is true for all search fields.

SEE ALSO

       L<audiolink(1)>, L<alfilldb(1)> The current version of this man page is available on the AudioLink website at
       <http://audiolink.sourceforge.net/>.

BUGS

       Report bugs related to the AudioLink software or the man pages to the audiolink-devel mailing list <audiolink-devel@lists.sourceforge.net>.

AUTHOR

       This manual page is written and maintained by Amit Shah <amitshah@gmx.net>

COPYRIGHT

       The AudioLink package is Copyright (C) 2003, Amit Shah <amitshah@gmx.net>. All the programs and the documentation that come as part of
       AudioLink are licensed by the GNU General Public License v2 (GPLv2).

perl v5.14.2							    2003-12-06							       ALSEARCH(1)