Shell Programming and Scripting

i have a file seperated each line seperated by newline. For example

Code:

alpha
beta
gamma

i am trying to replace the newlines to "," but dont want , present at the end of the line so i am trying the below one liner . but not sure whats wrong but its not working
cat myfile | tr -s '\n' ',' | sed 's/,$//'

But when i try it this way , its working
echo "alpha,beta,gamma," | sed 's/,$//'

can someone please explain me this behaviour.

Based exactly on your input file, it works for me. What is not working about it for you?

Code:

$ tr -s '\n' ',' < file | sed 's/,$//'    
alpha,beta,gamma

(no need for cat, though)

You can also use paste

Code:

$ paste -sd, file                     
alpha,beta,gamma

At a wild guess, I would say your file has ^M characters in it.

Show the output of:

Code:

cat -v infile

I would suggest your input file has some non-printing characters in it, most likley it's a DOS formatted file. Try running dos2unix on the file first or use:

Code:

tr -s '\r\n' ',' < myfile | sed 's/,$//'

In addition to the possibilities already listed, note that the standards only define the behavior of sed when the input is a text file. The output from the tr command is not a text file (by definition, the last character of a text file that is not an empty file is a <newline> character). The tr command you gave strips off the trailing <newline>; the echo command you gave supplies a trailing <newline>. If this is the problem, the tr|awk pipeline may work as you expect on some systems and produce no output at all (or do something completely different) on other systems.

Here are a couple of portable ways to do this:

Code:

awk 'NR==1{o = $0; next}
        {o = o "," $0}
END     {print o}' myfile

and:

Code:

#!/bin/ksh
(read o
while IFS="" read x
do      o="$o,$x"
done
printf "%s\n" "$o"
) < myfile

I use the Korn shell, but you can replace /bin/ksh in #!/bin/ksh with a path to any POSIX conforming shell on your system.

I have the file in unix system only and i dont see any any extra character. I am using solaris 10 .

Code:

# cat myfile
alpha
beta
gamma

# od -c myfile
0000000   a   l   p   h   a  \n   b   e   t   a  \n   g   a   m   m   a
0000020  \n
0000021
#

Code:

# tr -s '\n' ',' < myfile | sed 's/,$//'
#

I have tried this with bourne and bash shell. not same result.

sed path : /bin/sed

I tried with xpg4 path and output looks promising but with a warning message

Code:

# tr -s '\n' ',' < myfile | /usr/xpg4/bin/sed 's/,$//'
sed: Missing newline at end of file standard input.
alpha,beta,gamma

---------- Post updated at 03:16 PM ---------- Previous update was at 03:10 PM ----------

@Don Cragun your code worked. I am not able to get the point on why this behaviour is seen. why does a strip of trailing newlines piped to sed/awk wont work ?

The sed and awk utilities are only defined to work on text files. If the last line fed to sed or awk does not end in a <newline> character, the results are unspecified. Basically, sed and awk try to read in a line, and until they find the terminating <newline> character they don't have a line; so the partial line at the end of the file may be ignored as Solaris 10's /usr/bin/sed did. Or as Solaris 10's /usr/xpg4/bin/sed did; it can add the newline for you and warn you that it did so. Some versions of sed will silently add the trailing <newline> without a warning. Which behavior is better depends on the source of your data. (If your data source dies in the middle of transmitting/producing your data, the warning lets you know that data from the end of your input stream may have been lost.)

ok , so sed/awk have not worked in here as
tr output : alpha,beta,gamma, did not contain a new line in them. And this behaviour is also sed/awk version specific.
now with awk we can change the record seperator right ? so should not something like this work logically ?
since my tr output does not have a newline i am using RS=""

Code:

# tr -s '\n' ',' < myfile | awk 'BEGIN{RS=""}{sub(/,$/,"");print}'