UNIX for Dummies Questions & Answers

Hi! I'm using

echo $string | grep "[^0-9]" -c

to test in a script if a string is a number and it seems to work. But how can i find, for example, if a string is a four figures number ?

Thanks to all!

How does that command of yours test if the string is a number ? What it does is, it gives you a count of the number of non-numeric patterns found.

This will test a 4 digit string

Code:

echo $string | egrep "^[0-9]{4}$"

what is the goal ?
must your number be min 4 digits ?
must your number be min and max 4 digits ?

there are several options
I prefer the following

subtract 999 from your number and check the result to see if this is bigger than 0 => this way you know your number is at leaset 1000

subtract 9999 from your number and check the result to see if this is lower than 1 => this wat you know your number is max 9999

vb:

[dummy920]@@ecar0o:/home/oracle> t=8
[dummy920]@@ecar0o:/home/oracle> ((a=$t-999))
[dummy920]@@ecar0o:/home/oracle> if (( $a > 0 ))
more>then
more>echo "min 4 digits"
more>else
more>echo "too small"
more>fi
too small
[dummy920]@@ecar0o:/home/oracle> t=10000
[dummy920]@@ecar0o:/home/oracle> ((a=$t-9999))
[dummy920]@@ecar0o:/home/oracle> if (( $a < 1 ))
more>then
more>echo "max 4 digits"
more>else
more>echo "too big"
more>fi
too big