read a variable character by character, substitute characters with something else - UNIX for Dummies Questions & Answers

vipervenom25 · #1 (**permalink**) 06-06-2008

im having trouble doing this:

i have a variable with 2 characters repeating e.g. aababbbaaaababaabbaabbba

is there a way i can search the variable for a's and b's and then change a's to b's and b's to a's?

im guessing its like getting the 1's compliment of the string

im doing this in BASH, and ive looked into seeing if sed or awk could help but i got nothing

any help would be greatly appreciated
thanks

fabtagon · #2 (**permalink**) 06-06-2008

echo $var | tr a z | tr b a | tr z b

more info: man tr
we use z as temporary placeholder as we can only transform one character a time

joeyg · #3 (**permalink**) 06-06-2008

In order to switch things, the first cannot immediately be switched to the second. Take a look at the following where I ...
translate a to z
translate b to a
translate z to b

Code:

> echo $var1
aababbbaaaababaabbaabbba
> var2=$(echo $var1 | tr a z)
> var3=$(echo $var2 | tr b a)
> var4=$(echo $var3 | tr z b)
> echo $var4
bbabaaabbbbababbaabbaaab

More UNIX and Linux Forum Topics You Might Find Helpful
Thread	Thread Starter	Forum	Replies	Last Post
Can i read a file character by character	karnan	Shell Programming and Scripting	6	05-18-2008 11:22 PM
bash while read how to remove \n character	papasj	Shell Programming and Scripting	2	02-24-2008 08:01 AM
Read First Character of Each Line in File	azelinsk	Shell Programming and Scripting	7	07-11-2007 05:15 PM
Can I read a file character by character?	murtaza	Shell Programming and Scripting	3	03-29-2007 08:19 AM
need to read 3° character from a text file	piltrafa	UNIX for Dummies Questions & Answers	15	07-26-2005 07:19 AM

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode