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Creating a secret code converter

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Top Forums Shell Programming and Scripting Creating a secret code converter
# 1  
Old 10-27-2012
Tools Creating a secret code converter
Bashers, thanks for taking the time to look at my post.

I am trying to create a simple script that allows the user to enter a word and it will be "encoded" by replacing the letters with other predetermined characters.

I am attempting to run one long sed command through a text file that contains a user inputted string. What is happening is that its making multiple changes to one character instead of changing the character just once. How can I tell sed to basically change a character once but not again after it has been changed.
Code:
#!/bin/bash
clear
echo -ne "Enter word you want to encode: "
read userinput
echo "$userinput" > userinputtmp


sed -i 's/a/z/g; s/b/y/g; s/c/x/g; s/d/x/g' ......etc..... userinputtmp

echo -ne "The secret code is "
cat userinputtmp
rm userinputtmp
echo ""

Thanks for taking a look!
Last edited by rgrmatt; 10-27-2012 at 03:42 PM..
# 2  
Old 10-27-2012
This is a lengthy and surprising approach. Does you sed version provide the y command:
Code:
y/source/dest/
              Transliterate the characters in the pattern space which appear in source to the corresponding character in dest.

. Did you consider using the tr command for the same purpose?
This User Gave Thanks to RudiC For This Post:
rgrmatt
# 3  
Old 10-27-2012
RudiC,

Thanks for helping. Currently my sed command does not support '-y'. I am new to scripting like a lot of other users I see on this site. The tr function is new to me I will have to do some research on it. Would you think tr is a better way to reach my goal?
# 4  
Old 10-27-2012
Suggestion:

1. You can create a file: key.txt which has data about which char to replace.

E.g. I created a file: key.txt with following data:-

Code:
cat key.txt
a=z
b=y
c=x
d=w
e=v
f=u
g=t
h=s
i=r
j=q
k=p
l=o
m=n
n=m
o=l
p=k
q=j
r=i
s=h
t=g
u=f
v=e
w=d
x=c
y=b
z=a

2. Then you can use this file to replace your input string by reading character by character:-

Code:
#!/bin/bash
clear
echo -ne "Enter word you want to encode: "
read userinput
echo "$userinput" > userinputtmp

while read -n1 char # Reading input char by char
do
        rep_char=`awk -v CHR=$char -F"=" ' { if($1==CHR) print $2; } ' key.txt` # Getting the character to be replaced.
        echo -e "$rep_char\c" >> tmp # Replacing and writing it to a tmp file.
done < userinputtmp

mv tmp useroutputtmp

cat useroutputtmp

I hope it helps.
This User Gave Thanks to Yoda For This Post:
rgrmatt
# 5  
Old 10-27-2012
Quote:
Originally Posted by rgrmatt
Currently my sed command does not support '-y'.
It's not a -y command line option. The y is a function/command that's part of the sed script language. Your sed most likely supports it.
To change all a's to b's and all b's to c's without unintentially converting all a's to c's in the process:
Code:
sed 'y/ab/bc/'

Quote:
Originally Posted by rgrmatt
The tr function is new to me I will have to do some research on it. Would you think tr is a better way to reach my goal?
If this is all you need sed to do, swap one character for another, then, yes, tr is the most natural choice for the job. However, for such a simple case, using sed's y command is perfectly fine.

Regards,
Alister
Last edited by alister; 10-27-2012 at 06:06 PM..
This User Gave Thanks to alister For This Post:
rgrmatt
# 6  
Old 10-27-2012
Quote:
Originally Posted by rgrmatt
RudiC,

Thanks for helping. Currently my sed command does not support '-y'. I am new to scripting like a lot of other users I see on this site. The tr function is new to me I will have to do some research on it. Would you think tr is a better way to reach my goal?
I'm not sure what your goal would be. If I interpret correctly, you want to replace a by z, b by y, c by x, ... , x by c, y by b, z by a. This will not work the way you set about. Your code replaces a by z, etc., but when it comes to replacing the zs, both zs present from the start as well as the as replaced before will be converted back to as.
Try
Code:
tr 'abc...xyz' 'zyx...cba' <file1 >file2

or, even shorter,
Code:
tr 'a-z' 'zyx...cba' <file1 >file2

. Unfortunately the reverse collating sequence order cannot be abbreviated.
This User Gave Thanks to RudiC For This Post:
rgrmatt
# 7  
Old 10-27-2012
@bipinajith - Thank you so much, I will try this method if I cant figure out how to get
Code:
tr

to work.

@alister - Thank you for correcting me. Once I get back to my Linux box I am going to give this a shot also.

@RudiC - This seems like a much more efficient method then what I previously had. I am also going to try this.

I am extremely appreciative for all your input. I hope this thread aids any new scripters out there.

---------- Post updated at 05:19 PM ---------- Previous update was at 05:06 PM ----------

Quote:
Originally Posted by RudiC
I'm not sure what your goal would be. If I interpret correctly, you want to replace a by z, b by y, c by x, ... , x by c, y by b, z by a. This will not work the way you set about. Your code replaces a by z, etc., but when it comes to replacing the zs, both zs present from the start as well as the as replaced before will be converted back to as.
Try
Code:
tr 'abc...xyz' 'zyx...cba' <file1 >file2

or, even shorter,
Code:
tr 'a-z' 'zyx...cba' <file1 >file2

. Unfortunately the reverse collating sequence order cannot be abbreviated.
This worked best thank you! My script is complete

I basically did what you said but I piped it into an echo statement...

Code:
echo $userinput | tr 'a-z' 'zxy...cba'
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