How to select or make reference to, part of a field

Shell Programming and Scripting
1

For a field format such as AAL1001_MD82, how do I select(and use in if statement) only the last four elements( in this case MD82) or the first three elements (in this case AAL)?

For instance, how do I do the following - if first three elements of $x == yyy, then ...

2

If you have bash: ${variable:start:length}
length is optional.

stringZ=abcABC123ABCabc
#       0123456789.....
#       0-based indexing.

echo ${stringZ:0}                            # abcABC123ABCabc
echo ${stringZ:1}                            # bcABC123ABCabc
echo ${stringZ:7}                            # 23ABCabc

echo ${stringZ:7:3}                          # 23A
                                             # Three characters of substring.
pos=$((  ${#stringZ} - 3 ))

echo ${stringZ:$pos}                # last three characters
3

use cut

[tpntvkc]:tpntvkc> echo abcdefgh | cut -c 1-4
abcd

4

This does not work while using awk. How do I do this in awk?

Thanks

5

Try this:

> echo AAL1001_MD82 | /usr/xpg4/bin/awk ' { print substr($0,length($0)-3,4) }'
MD82
6

Thanks, that works!