Shell Programming and Scripting

Hi Gurus,

I am stuck on below issue.
in my .profile. I have two variable:

Code:

 
x=abc$123 
t=xyz$

when running env command, I got below:

Code:

 
x=abc
t=xyz$

my OS is SunOS 5.10 sun4v sparc SUNW,SPARC-Enterprise-T5220

I am wondering why t=xyz$ shows exactly value?

I try below:

Code:

 
par1=xyz
export par1
par2=123$par1
export par2

I got below:

Code:

 
par1=xyz
par2=123xyz.

thanks in advance

Code:

x=abc$123 
t=xyz$

x gets the assignment value of the string abc and the dereference of the variable $123, which if it is not set it would be undefined.

t gets the assignment value of the string xyz$. The `$' is not being interpreted by the shell as the dereference of a variable, since it exist as the last character. It is the equivalent of 'xyz$' or xyz\$

ken6503,
You haven't said which shell you're using.

I have forgotten how /bin/sh will expand $123 but I thought that:

Code:

x=abc$123

would assign x the string abc followed by the contents of the 1st positional parameter followed by the string 23. I don't know why you didn't get the 23? If you were trying to set x to the literal string abc$123, you could do that with any of the following:

Code:

x=abc"$"123
x='abc$123'
x=abc\$123

or millions of variations of any of those three possibilities.

There is nothing special about a dollar sign at the end of a string (unless the string ends with $$, so the code:

Code:

t=xyz$
echo "$t"

should produce the output:

Code:

xyz$

I can't imagine that any shell, when given the commands:

Code:

par1=xyz
export par1
par2=123$par1
export par2

will produce the period you showed us at the end of the output you reported:

Code:

par1=xyz
par2=123xyz.

Aia,
No, $123 does not expand to the value of the 123rd positional parameter; it expands to the value of the 1st positional parameter followed by the string 23. To get the 123rd positional parameter with a POSIX conforming shell, you would need to use ${123}. With a pure Bourne shell you can't reference any positional parameters after the 9th positional parameter directly without shifting away lower positional parameters.

And, expanding an undefined variable (including positional parameters) produces an empty string; not some undefined value.

Don,
Thank you for correcting that, somehow I forgot that normal variable names start with letters or underscore, thus my premises were wrong, since I was considering abc$123 as the shell trying to interpret abc$var
Just bad wording. I meant the variable does not exist. It is undeclared. The variable itself, not the value it can produce.

Thanks Don for your reply. My OS is Solaris.

shell is ksh.
please see attached screenshot.

And the thumbnail shows exactly what I said you should get for the things you showed us.

You said you got:
par2=123xyz.
I said the period shouldn't be there. The period is not there in the screenshot.

You didn't show us in that screenshot what happens with the following commands:

Code:

x=abc$123
echo "$x"

You said you got:
abc
I said that instead, it should have produced:
abcsome(possibly empty)string23
where some(possibly empty)string should be the same thing you get from:
printf '%s\n' "$1"

Thanks Don for your reply.
Sorry, I misunderstood you. the period is type.

when I try

Code:

par2=abc$123
export par2

I got
when trying

Code:

part=abc$xyz
export par2

I got

Code:

abc

could you please give me a brief explanation about this? thanks.