## if/elif help

# 1
06-27-2011
if/elif help

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1. The problem statement, all variables and given/known data:
This is my problem for the class.

Write a script that asks for the user's age. If it is equal to or higher than 16, print a message saying that
this user is allowed to drink alcohol. If the user's age is below 16, print a message telling the user how
many years he or she has to wait before legally being allowed to drink.
As an extra, calculate how much beer an 18+ user has drunk statistically (100 liters/year) and print
this information for the user.

I can make it do the if older than 16 then you can drink
Also If you are 15 or younger than you have to wait X years until you can drink

My problem id with the calculation of how many liters you have drank since 18+.

2. Relevant commands, code, scripts, algorithms:
if/elif commands

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):
Oklahoma State Institute of Technology
Okmulgee, Oklahoma
USA
Professor Fil Guinn
ITD 2313-SCRIPT PROGRAMMING-SEC LECNT1

Note: Without school/professor/course information, you will be banned if you post here! You must complete the entire template (not just parts of it).

Last edited by pludi; 06-27-2011 at 07:10 AM..
 aggie6970 View Public Profile for aggie6970 Find all posts by aggie6970
# 2
06-27-2011
... but if you don't use \$myvar2 anywhere else in your script, then calculating it is useless .

Last edited by ctsgnb; 06-27-2011 at 06:58 AM..
 ctsgnb View Public Profile for ctsgnb Find all posts by ctsgnb
# 3
06-27-2011
Quote:
Originally Posted by ctsgnb
... but if you don't use \$myvar2 anywhere else in your script, then calculating it is useless .
\$ inside a (( )) block is redundant. So are mathematical assignments outside it.

 Corona688 View Public Profile for Corona688 Visit Corona688's homepage! Find all posts by Corona688
# 4
06-28-2011
Quote:
Originally Posted by Corona688
\$ inside a (( )) block is redundant. So are mathematical assignments outside it.

most times your are right.but some older version of sh(like ash , that is usually not Posix compliant on many systems) your syntax is invalid.
[[ *maybe it is various of evulation expression bug of a ash.]]
(so its meant some older versions of (bourne) sh(s) like (0.38) has it, and i cannot test newer version ash(0.4 or newer if there is) so ash is not compability to SUSv3.

actually aritmetic expansion is defined for SUSv3
`Arithmetic Precision and Operations`
in Introduction
`2.6.4 Arithmetic Expansion`
in Shell Command Language]

now lets look at the belows..
[not expanded values before aritmetic expression]
it is required a `\$` before variables

in sh another interesting issue
--try 1
--try 2
--try 3 is like OK , but?
but is not.
regards
ygemici
 ygemici View Public Profile for ygemici Find all posts by ygemici
# 5
06-29-2011
Quote:
Originally Posted by ygemici
--try 2
--try 3 is like OK , but?
but is not.
regards
ygemici
Try removing the \$ from the x. It evaluates into 1=5, which naturally doesn't work.
 Corona688 View Public Profile for Corona688 Visit Corona688's homepage! Find all posts by Corona688
# 6
07-05-2011
You guys are conflating two different POSIX shell mechanisms here. One is the arithmetic expansion and the other is command expansion. These are different.

\$(()) denotes arithmetic expansion, and \$() denotes command expansion.

Shells that support \$() or \$(()) generally support both. For older shells that do not support these syntaxes, you need to use backticks (`) for command expansion and arithmetic expansion isn't supported. In arithmetic expansion, Corona rightly reports that you do not need \$ to expand variables; however, you do need this in command expansion. For example:
However:
OTOH, if we give it an expr command:

We need explicit variable expansion:
BTW, if we want compatibility with older shells that do not support arithmetic expansion, we generally are not going to be able to use new-style command expansion, so we want something like this, instead:

 Morgan Greywolf View Public Profile for Morgan Greywolf Find all posts by Morgan Greywolf
# 7
07-05-2011
Quote:
Originally Posted by Morgan Greywolf
You guys are conflating two different POSIX shell mechanisms here. One is the arithmetic expansion and the other is command expansion. These are different.

\$(()) denotes arithmetic expansion, and \$() denotes command expansion.

Shells that support \$() or \$(()) generally support both. For older shells that do not support these syntaxes, you need to use backticks (`) for command expansion and arithmetic expansion isn't supported. In arithmetic expansion, Corona rightly reports that you do not need \$ to expand variables; however, you do need this in command expansion. For example:
However:
OTOH, if we give it an expr command:
We need explicit variable expansion:
BTW, if we want compatibility with older shells that do not support arithmetic expansion, we generally are not going to be able to use new-style command expansion, so we want something like this, instead:

we dont conflating anything.we are talking just arithmetic expansion about all shell variants.
I was referring to mentioned syntax of "\$((x+y))" expression gives error on the some older shells..
In addition, I mentioned what i identified a issue that is maybe a bug in ash.
because of it(false statement) does not give any error at try of 3rd.

regards
ygemici
 ygemici View Public Profile for ygemici Find all posts by ygemici

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