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A bug in "tr" command ???

From: RLambert1
Subject: A bug in "tr" command ???
Date: Tue, 30 Sep 2003 04:47:48 EDT

Hello.  I hope this is not a bug, that I'm just doing something wrong.  
Anyway, here's how this "journey" started.  I had a file with carriage return 
characters (^M) in it.  The file was one LONG record, and I wanted newline 
characters where the ^M's were.  I thought I could just set awk's RS variable 
to ^M, 
and that would do it.  But, I needed a way to "create"
the ^M character.

Somewhere on the Internet I found this:

cm=`echo m | tr 'm' '\015'`

but, that did not seem to work.  Seemed like "cm" ended up being null.  To 
test if the syntax of the command correct, I did the following:

Script 1 (a file called ASCII):

cat /dev/null > asc
cat /dev/null > asc.txt

for i in 000 001 002 003 004 005 006 007 \
         010 011 012 013 014 015 016 017 \
         020 021 022 023 024 025 026 027 \
         030 301 032
   echo "x=\`echo x | tr 'x' '\\${i}'\`" >> asc
   echo "echo \"\${x}\" >>asc.txt" >>asc

bash asc

The execution of script 1 (ASCII) created a file called asc
(which was executed from within the ASCII file).

asc file:

x=`echo x | tr 'x' '\000'
if [[ "${x}" == "" ]]; then echo "x is null"; else echo "x is not null"; fi
#Note: the above "if" statement was not created by the script.  I edited it 
in afterwards,
#and re-executed the asc file manually
echo "${x}" >>asc.txt
x=`echo x | tr 'x' '\001'
if [[ "${x}" == "" ]]; then echo "x is null"; else echo "x is not null"; fi
#Same for that "if" statement, too
echo "${x}" >>asc.txt
x=`echo x | tr 'x' '\002'
echo "${x}" >>asc.txt
    . (several lines left out for brevity)
x=`echo x | tr 'x' '\031'
echo "${x}" >>asc.txt
x=`echo x | tr 'x' '\032'
echo "${x}" >>asc.txt

And, the result of that execution was a file, asc.txt
(this is how it looked when viewed with vi):

(a null character, OK, i.e., expected)
(a tab character, OK, i.e., expected)
(a null character, not expected)
(a null character, not expected, at least I had hoped it would be a ^M)
.(several lines left out for brevity)

Note 1:  where ^I would be is a tab character (OK)
         where ^J would be is a null character
         where ^M would be is a null character

Note 2:  I went back and edited in the following line to the
         2nd file (asc):

if [[ "${x}" == "" ]]; then echo "x is null"; else echo "x is not null"; fi

and inserted it after the "000", "001", "012", "013", "015", and "016" lines 
to test.  The character created by the "012", and "015" lines from the asc 
file is null.  :(

Note 3:  GNU bash, version 2.05.0(8)-release (i686-pc-cygwin)

Note 4:  I finally just made a copy of a file that had ^M's in it, edited out 
everything but one ^M character, and then edited the following around the ^M:

BEGIN { RS = "^M" }
{ print }

and then used that to process my file with the ^M's in it:

cat ctrl-Ms_file | awk -f RS_is_ctrl-M.awk > newlines_file

Yucky thing is that I would have to keep that "RS_is_crtl-M.awk" file around 
(or create it as needed using vi) since I can't create a ^M character "on the 
fly".  :(


Richard Lambert

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