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Full Discussion: escape sequence for $
Top Forums Shell Programming and Scripting escape sequence for $ Post 302229074 by drl on Tuesday 26th of August 2008 06:10:46 AM
Old 08-26-2008
Hi.
Quote:
name
A word consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore. Names are used as shell variable and function names. Also referred to as an identifier.

-- excerpt from Bash Reference Manual
Note that the $ is not listed.

There is a way that the look of your requirement can be done -- essentially as an indirect assignment:
Code:
#!/bin/bash -

# @(#) z1       Demonstrate indirect assignment.

echo
a=0
b=1
a=b
echo " first assignment a = $a, b = $b"

echo
$a=2
echo " second assignment a = $a, b = $b"

echo
eval $a=2
echo " eval assignment a = $a, b = $b"

exit

Producing:
Code:
% ./z1

 first assignment a = b, b = 1

./z1: line 12: b=2: command not found
 second assignment a = b, b = 1

 eval assignment a = b, b = 2

However, in general, $ is used as the dereferencing operator in shells. In elementary perl, it must be used to identify scalar variables ... cheers, drl
 

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readonly(1)							   User Commands						       readonly(1)

NAME
readonly - shell built-in function to protect the value of the given variable from reassignment SYNOPSIS
sh readonly [name...] ksh **readonly [ name [ = value]...] **readonly -p DESCRIPTION
sh The given names are marked readonly and the values of the these names may not be changed by subsequent assignment. If no arguments are given, a list of all readonly names is printed. ksh The given names are marked readonly and these names cannot be changed by subsequent assignment. When -p is specified, readonly writes to the standard output the names and values of all read-only variables, in the following format: "readonly %s=%s ", name, value if name is set, and: "readonly $s ", name if name is unset. The shell formats the output, including the proper use of quoting, so that it is suitable for reinput to the shell as commands that achieve the same value and readonly attribute-setting results in a shell execution environment in which: 1. Variables with values set at the time they were output do not have the readonly attribute set. 2. Variables that were unset at the time they were output do not have a value at the time at which the saved output is reinput to the shell. On this man page, ksh(1) commands that are preceded by one or two ** (asterisks) are treated specially in the following ways: 1. Variable assignment lists preceding the command remain in effect when the command completes. 2. I/O redirections are processed after variable assignments. 3. Errors cause a script that contains them to abort. 4. Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a vari- able assignment. This means that tilde substitution is performed after the = sign and word splitting and file name generation are not performed. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
ksh(1), sh(1), typeset(1), attributes(5) SunOS 5.10 17 Jul 2002 readonly(1)
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