set x=“abc def”tcshThe double quotes resolve all variables within the string. Here is an example
for pdksh and bash:
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var="test string"
newvar="Value of var is $var"
echo $newvar
Here is the same example for tcsh:
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set var="test string"
set newvar="Value of var is $var"
echo $newvar
If you execute a shell program containing the preceding three lines, you get
the following result:
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Value of var is test string
Using Single Quotes to Maintain Unexpanded Variables
You can surround a string with single quotes (’) to stop the shell from
expanding variables and interpreting special characters. When used for the
latter purpose, the single quote is an escape character, similar to the
backslash, which you learn about in the next section. Here, you learn how to
use the single quote to avoid expanding a variable in a shell script. An
unexpanded variable maintains its original form in the output.
In the following examples, the double quotes from the preceding examples
have been changed to single quotes:
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pdksh and bash:
var='test string'
newvar='Value of var is $var'
echo $newvar
tcsh:
set var = 'test string'
set newvar = 'Value of var is $var'
echo $newvar
If you execute a shell program containing these three lines, you get the
following result: