UNIX for Dummies Questions & Answers

Hi All,

I would like to know how, iff at all we can, we may use the 'tr' command to replace a single character with multiple characters.

eg: if i have a string valued "him", how can i use 'tr' to replace 'i' with "oo" to make "hoom".

Just replacing a single character by many.
tried:-

Code:

echo "him" | tr 'i' 'oo'

but this results in "hom". Please guide.

Thank you.

you want it from tr only because i suggest sed will be the better option

Hi Vidya,

Thanks for the suggestion. Then pls let me try with sed myself first and I ll get back to you if unable to.

Thank You.

Hi I tried using sed and following are the problems I faced:

1. sed operates on a file, I have to take value from a variable.
2. actually I need to replace '/' by '\/'. Here is some more detail if I am following the wrong track:

actually I have written a script that works on a file having attribute,value pairs in the format :
attribute= value
i have to search for an attribute and update it's value, iff the attribute and the file requested are found.

Now there are certain attributes which have paths, eg : source= /usr/java14/bin
If the user wants to update this value, according to the current script he needs to be intelligent enough to write the new value as \/usr\/bin, for example... i.e the user himself escapes all the '/'.

But i want to make it easy for the user, I hope I have explained my problem.
So how shall I approach?
(Pls avoid giving solutions directly and only hint, I want to trouble my brain)

What about using awk?
You have your script and the var_name1 you want to change; so match on that.
You know new_val2, so place that in the output of the awk print.

ok, to start you, and the following is not 'good syntax'

change_file looks like
var_qtr_file*/home/joe/qtr_2008
time_year_end*/users/somewhere/year2009

Code:

read change_file to line
var_name1=$(echo $line | cut -d"*" -f1)
new_val2=$(echo $line | cut -d"*" -f2)

now do your awk
(you could have done previous in awk too!)
figure out what needs to change
write new dataline out

use this sed cmd
echo "him"|sed 's/i/oo/'

Hi

Thanks for the valuable inputs. I have tried with sed as directed, worked. Now I am trying to use it in a similar way to get the exact solution

Replacing '/' by '\/'

I have tried:

Code:

sed 's/'\/'/'\\/'/' tmp.txt

this cannot be parsed as unix reads it as :

Code:

s///\//

Also i have tried to use the octal value of '/' i.e. :

Code:

echo "h/im" | sed 's/'\\057'/'p'/'

Accordingly, "h/im" must change to "hpim" but it does not change anything because it reads as

Code:

s///p/

I think I need to insert some single quotes by escaping, I ll get back after I ve tried. Pls correct me if I have gone wrong anywhere.

I did not try the awk because I am not familiar with awk, not UNIX either for that matter. I ll take that path once I have some idea of awk.

Thank You.