Homework & Coursework Questions

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1. The problem statement, all variables and given/known data:
Hi I am new to unix and need some help, the main reason I am here is because i need basic unix knowledge
The question for university says this :

"If the command procedure contains the command echo $ {d-.} what will it bring?"
I tried googling it but no results where found, I asked in other forums but no one knew

Thanks for the help

2. Relevant commands, code, scripts, algorithms:



3. The attempts at a solution (include all code and scripts):



4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):
I am attending at the New Bulgarian University, Bulgaria, Sofia.
This question was made by professor Gadzev for the course CSCB58

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Moderator's Comments:

I have modified your post to fit the template that (in future) you must use when submitting in the homework forum.

Space characters are important.
I expect you mean:

Code:

echo ${d-.}

In words it means that the default value for the environment variable $d is a period character. So if there is nothing in $d the shell will put a period character in the variable for you.

Code:

For example:
unset d
echo ${d-.}
.

d=423
echo ${d-.}
423

You can easily find this information by reading the man page for the shell you are using.

From the man page, search for Parameter Expansion.

Code:

${parameter:-word}
              If parameter is set and is non-null then substitute its value; otherwise substitute word.
...
If the colon ( : ) is omitted from the above expressions, then the shell only checks whether parameter  is  set or not.