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UNIX script -- case

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# 8  
Old 02-01-2013
You could of course use trickery and process the number as if it were a string and do something like this:

Code:
case $1 in  
  [1-9]*) echo greater than or equal to 1 ;;
       *) echo less or equal ;;
esac

That would work if $1 is always a number, but it would make the code a bit less straight forward / more difficult to read and understand...
Last edited by Scrutinizer; 02-01-2013 at 07:06 AM..
# 9  
Old 02-01-2013
Quote:
Originally Posted by Scrutinizer
You could of course use trickery and process the number as if it were a string and do something like this:

Code:
case $1 in  
  [1-9]*) echo greater than or equal to 1 ;;
       *) echo less or equal
esac

That would work, but it would make the code less straight forward / more difficult to read and understand...
oh...that is nice ! um.. I am still a beginner. Is there a logical problem ?
Is [1-9]* = * ? If yes , whatever input , two arguments will be output

---------- Post updated at 06:08 AM ---------- Previous update was at 06:01 AM ----------

Quote:
Originally Posted by Scrutinizer
You could of course use trickery and process the number as if it were a string and do something like this:

Code:
case $1 in  
  [1-9]*) echo greater than or equal to 1 ;;
       *) echo less or equal ;;
esac

That would work if $1 is always a number, but it would make the code a bit less straight forward / more difficult to read and understand...
i try it and it is work . thanks a lot .
that little strange for me [1-9]* is not equal to *
# 10  
Old 02-01-2013
[1-9]* is not equal to *, it is a unix pattern that matches strings that start with 1,2,3,4,5,6,7,8 or 9
# 11  
Old 02-01-2013
Quote:
Originally Posted by Scrutinizer
[1-9]* is not equal to *, it is a unix pattern that matches strings that start with 1,2,3,4,5,6,7,8 or 9
Thank you for you patient.
But i still have some questions .
As u say , asterisk matches 1 to 9 , even any variables .
Why the result is not
Code:
less or equal

but first argument ?
um..that is suprise me the program is totally fit , second argument is out when zero or negative values is input.
# 12  
Old 02-01-2013
Because the first pattern matches ([1-9]*), the second pattern (*) does not get evaluated.
This User Gave Thanks to Scrutinizer For This Post:
SSUUser
# 13  
Old 02-01-2013
Quote:
Originally Posted by Scrutinizer
Because the first pattern matches ([1-9]*), the second pattern (*) does not get evaluated.
o.yes..! That means if
*) echo .... ;;
places first
result must be the first one whatever input is .
Thank you much u telling me that .!
thank you
# 14  
Old 02-01-2013
As scrutinizer stated, the point is that [1-9]* is interpreted by the shell as a unix pattern ( matching any string starting with a figure from 1 to 9)

And NOT as a regular expression (matching 0 or more figures that are in the interval from 1 to 9 )

You can easily test it with empty string or strings like "9a" an check whether it matches or not
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