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Full Discussion: Simple Variable substitution in ksh not working
Top Forums Shell Programming and Scripting Simple Variable substitution in ksh not working Post 302961000 by Don Cragun on Monday 23rd of November 2015 02:53:41 AM
Old 11-23-2015
mukesh.lalwani,
With any Korn shell, you can use arrays with a numeric subscript for subscripts from 0 to about 2047. With ksh93 and with bash you can use numeric subscripts with larger values or with string valued subscripts. The syntax is:
Code:
$ i=1
$ dbname[1]="tree"
$ echo "${dbname[$i]}"
tree
$

or for multiple array elements:
Code:
$ dbname=("forest" "tree")
$ for ((i = 0; i < ${#dbname[@]}; i++))
> do	printf 'dbname[%d]="%s"\n' "$i" "${dbname[$i]}"
> done
dbname[0]="forest"
dbname[1]="tree"
$

Or, with any shell based on Bourne shell syntax, you can use eval as shown in the link you referenced. Note that eval can be a security risk if any of the code that you are feeding to eval is supplied by a user. But, eval is generally safe if all of the strings being evaluated by eval are hardcoded into your script.

RTY,
Code:
$ echo $dbname$i

prints whatever $dbname expands to followed by whatever $i expands to not to the contents of the variable named by dbname followed by the expansion of $i.

And:
Code:
$ echo ${dbname$i}
ksh: syntax error: `$' unexpected
$

doesn't work either.
 

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LEARN ABOUT REDHAT

droplang

DROPLANG(1)						  PostgreSQL Client Applications					       DROPLANG(1)

NAME

       droplang - remove a PostgreSQL procedural language

SYNOPSIS

       droplang [ connection-options... ] langname [ dbname ]

       droplang [ connection-options... ]  --list | -l dbname

DESCRIPTION

       droplang is a utility for removing an existing programming language from a PostgreSQL database.	droplang can drop any procedural language,
       even those not supplied by the PostgreSQL distribution.

       Although backend programming languages can be removed directly using several SQL commands, it is recommended to	use  droplang  because	it
       performs a number of checks and is much easier to use. See DROP LANGUAGE [drop_language(7)] for more.

OPTIONS

       droplang accepts the following command line arguments:

       langname
	      Specifies the name of the backend programming language to be removed.

       [-d] dbname

       [--dbname] dbname
	      Specifies  from which database the language should be removed.  The default is to use the database with the same name as the current
	      system user.

       -e

       --echo Displays SQL commands as they are executed.

       -l

       --list Shows a list of already installed languages in the target database (which must be specified).

       droplang also accepts the following command line arguments for connection parameters:

       -h host

       --host host
	      Specifies the host name of the machine on which the server is running. If host begins with a slash, it is used as the directory  for
	      the Unix domain socket.

       -p port

       --port port
	      Specifies the Internet TCP/IP port or local Unix domain socket file extension on which the server is listening for connections.

       -U username

       --username username
	      User name to connect as

       -W

       --password
	      Force password prompt.

ENVIRONMENT

       PGDATABASE

       PGHOST

       PGPORT

       PGUSER Default connection parameters.

DIAGNOSTICS

       Most error messages are self-explanatory. If not, run droplang with the --echo option and see under the respective SQL command for details.
       Check also under psql(1) for more possibilities.

NOTES

       Use createlang(1) to add a language.

EXAMPLES

       To remove pltcl:

       $ droplang pltcl dbname

SEE ALSO

       createlang(1), DROP LANGUAGE [drop_language(7)]

Application							    2002-11-22							       DROPLANG(1)
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