Shell Variables (Revision #13)

FluidShell supports shell variables similar to Bash.

There are multiple ways to create (both local and global) variables in FluidShell.

1. declare and set

:$ declare myvar='My Value'

The above command would declare a local variable which is not available to child processes such as those opened via exec command.

set is an alias for declare command which also performs exactly the same function.

To set global variables such as those that could be used by child sub-processes, you can use the -x attribute along with the declare command.

:$ declare -x myGvar='My Value'

2. ask

ask allows you to define a variable interactively i.e you can prompt the user for its (variable) value at runtime.

:$ ask -m "Enter value:" myVar
Enter value:Hello World!
:$ echo $myVar
Hello World!

3. A third convenient way to create variables is to use the export command. It works in pretty much the same way as declare, however it creates a global variable implicitly.

To list all variables within the current shell, you may execute set or declare or export

:$ set
CLI_SHELL_LINE_INTERPRETER_ERROR_ON_EXPLICIT_CMD_NOT_FOUND=true
CLI_SHELL_LINE_INTERPRETER_EVAL_COMMENT=sql
CLI_SHELL_LINE_INTERPRETER_EVAL_EXPLICIT_CMD=true
CLI_SHELL_LINE_INTERPRETER_EVAL_EXPLICIT_SQL=false
CLI_SHELL_LINE_INTERPRETER_EVAL_HISTORY=true
CLI_SHELL_LINE_INTERPRETER_EVAL_IMPLICIT_CMD=true
CLI_SHELL_LINE_INTERPRETER_EXPLICIT_CMD_CHAR=\
CLI_SHELL_LINE_INTERPRETER_EXPLICIT_SQL_CHAR=;
CLI_SHELL_LINE_INTERPRETER_IMPLICIT_BEHAVIOR=sql
CLI_SHELL_LINE_INTERPRETER_IS_AT_SIGN_GO=true
CLI_SHELL_LINE_INTERPRETER_IS_FORWARDSLASH_GO=true
CLI_SHELL_LINE_INTERPRETER_IS_SEMICOLON_GO=false
CLI_SHELL_LINE_INTERPRETER_PERFORM_ALIAS_EXPANSION=true
CONNECTIONS=C:\Users\vikram\.datastudio\connections

As shown above, to print the value of a variable;

:$ echo $CLI_SHELL_LINE_INTERPRETER_IMPLICIT_BEHAVIOR
sql

Please note ${myVar} and $myVar are same within the context of FluidShell.

FluidShell provides the flexibility to execute SQL commands within the same shell along with standard Bash commands and thus also allows the shell variables to be used within SQL statements directly. The only caveat being that the variables should follow the ${myVar} syntax (with the braces). For instance;

:$ set name=Orders
:$ select * from ${name} << please note the use of braces here
:$ go

Variable expansion in SQL statements can be disabled by setting the SQL_VARIABLE variable to "0".

:$ set | grep SQL_VARI
:$ set SQL_VARIABLE=0

At times it may be required to remove or un-set a variable, FluidShell caters to this by providing the unset command

:$ echo $myVar1
My VAR 1
:$ unset myVar1
:$ echo $myVar1

:$ 

Special note on Quotes

When setting variable values please note the single (') and double (") quote escape pattern which are similar to Bash.  Single quoted strings are literal values, while double quoted strings expand the special characters. For instance:

:$ declare myVar1="My VAR 1"
:$ echo $myVar1                                                          
My VAR 1
:$ echo "$myVar1"                                                                     
My VAR 1
:$ echo '$myVar1'                                                                     
$myVar1 << Expanded literally

Another example:

:$ declare myNewVar="$myVar1 Again"                                                    
:$ echo $myNewVar                                                                     
My VAR 1 Again << myVar1 expanded

Some observations regarding behaviour of quotes

• Enclosing characters in double quotes preserves the literal value of all characters within the quotes; with the exception of $, ` (backtick), \, and ! (when history expansion is enabled).

• The characters $ and ` retain their special meaning within double quotes. The backslash retains its special meaning only when followed by one of the following characters: $, `, ", \, or \n.

• A double quote may be quoted within double quotes by preceding it with a backslash. If enabled, history expansion will be performed unless an ! appearing in double quotes is escaped using a backslash. The backslash preceding the ! is not removed.

 

Aliases

The following table lists command aliases defined in the FluidShell:

 

Alias	Command
go	\go
GO	\go
ls	\ls -l
man	\help
set	\declare

 

Variables

The following table defines pre-set variables and their function.

CONNECTIONS	Provides the directory name for "Local Database Servers" folder.
DATABASE	Contains database name which will be used by \connect and \reconnect commands.
HISTFILE	Provides the location of the command buffer file.
HISTSAVE	Determines whether the command history should be saved on disk or not.
HISTSIZE	Number of lines to be kept in the command history buffer.
LINENO	An internal variable which contains the current line number within the SQL buffer.
MAX_ROWS	Determines the maximum number of rows returned by the \go command.
PROMPT	Allows changing the command prompt.
SERVERNAME	This variable contains the current connection server name, when connected.
SHELL_VERSION	Contains the FluidShell version number.
SQL_VARIABLES	Determines whether the variables should be expanded in SQL statements or not.
USERNAME	This variable contains the current connection user name, when connected.

 

CLI

The following are the default settings for the Command Line Shell mode. These determine how \cli shell interprets sql statements and commands. See the \cli page for more on the three available modes ( \cli fluid, \cli shell, \cli sql). By default, the FluidShell is in \cli fluid mode.

CLI_SHELL_LINE_INTERPRETER_ERROR_ON_EXPLICIT_CMD_NOT_FOUND="true"	Reports an error if it cannot find an explicit command that is preceded by \
CLI_SHELL_LINE_INTERPRETER_EVAL_COMMENT="shell"	Evaluates a line to a comment with a leading #
CLI_SHELL_LINE_INTERPRETER_EVAL_EXPLICIT_CMD="true"	Allows use of fluidshell commands without a preceding \
CLI_SHELL_LINE_INTERPRETER_EVAL_EXPLICIT_SQL="true"	Disables explicit SQL, meaning the preceding character in CLI_SHELL_LINE_INTERPRETER_EXPLICIT_SQL_CHAR=""  is required for interpreting SQL statements
CLI_SHELL_LINE_INTERPRETER_EVAL_HISTORY="true"	Enables the command history
CLI_SHELL_LINE_INTERPRETER_EVAL_IMPLICIT_CMD="true"	Evaluates commands when they are not preceded by \
CLI_SHELL_LINE_INTERPRETER_EXPLICIT_CMD_CHAR="\\"	Determines which character must precede a command for it to be interpreted when CLI_SHELL_LINE_INTERPRETER_EVAL_EXPLICIT_CMD="true"
CLI_SHELL_LINE_INTERPRETER_EXPLICIT_SQL_CHAR=";"	Determines which character must precede an SQL statement for it to be interpreted when CLI_SHELL_LINE_INTERPETER_EVAL_EXPLICIT_SQL="true"
CLI_SHELL_LINE_INTERPRETER_IMPLICIT_BEHAVIOR="shell"	Determines which mode
CLI_SHELL_LINE_INTERPRETER_IS_AT_SIGN_GO="true"	Determines if @ can be used as a statement separator
CLI_SHELL_LINE_INTERPRETER_IS_FORWARDSLASH_GO="true"	Determines if / can be used as a statement separator
CLI_SHELL_LINE_INTERPRETER_IS_SEMICOLON_GO="false"	Determines if ; can be used as a statement separator
CLI_SHELL_LINE_INTERPRETER_PERFORM_ALIAS_EXPANSION="true"	Allows alias expansion

 

SQL Results Options

You can set preferences using the \set command.

For example,

To display SQL Statement, use the command	\set CMD_GO_SHOW_SQL
Display column headers	\set CMD_GO_SHOW_COLUMNHEADERS
Display query statistics	\set CMD_GO_SHOW_QUERYSTATS
Display warnings	\set CMD_GO_SHOW_WARNINGS
Display warnings headers	\set CMD_GO_SHOW_WARNINGHEADERS
Always display 'records affected' count	\set CMD_GO_SHOW_ALWAYSDISPLAYSUCCESS
Display only the total number of affected records	\set CMD_GO_SHOW_SUM
Margin character length	\set CMD_GO_SHOW_MARGINCHARLENGTH
Display client statistics	\set CMD_GO_SHOW_CLIENTSTATS
Display SQL results as form entries	\set CMD_GO_SHOW_RESULTSASFORM
Display when execution stops on an error	\set CMD_GO_SHOW_EXEC_STOPONERROR