How to output comma separated values using IFS="," in shell

Question

I have a small script, which does not give comma separated output when IFS is used, but IFS is mandatory as i need it to read many other value. The output of the below script is odi_server1 odi_server2, but I need it separated by comma.

#Script Starts
#!/bin/sh
IFS=","
odi_cluster=odi_server1,odi_server2;
echo $odi_cluster;
#Script Ends

Current Output = odi_server1 odi_server2

Expected Output = odi_server1,odi_server2

Note:- IFS="," is mandatory, hence removing it is not an option.

The Input Field Separator is not used for output field separation. — ctrl-alt-delor, Oct 06 '20 at 21:04
Always double-quote your variables when you use them, i.e. echo "$odi_cluster" instead of echo $odi_cluster. — Chris Davies, Oct 06 '20 at 21:27
The shebang must be the first line in the file -- specifically, #! must be the first two characters in the script. — Paul_Pedant, Oct 06 '20 at 22:03
In the suggested duplicate, please read the accepted answer, and particularly the second paragraph of its point (1). — Chris Davies, Oct 06 '20 at 22:39
@Paul_Pedant the missing double-quotes coupled with the IFS value is exactly the problem — Chris Davies, Oct 06 '20 at 22:58
@roaima Conceded absolutely. As I always quote, and always set IFS as a local export only, I never ventured into this particular morass. — Paul_Pedant, Oct 07 '20 at 10:59
By the way, you probably could have found that out yourself had you searched for "IFS" in the bash man page and read through the first paragraph with a match. — Johannes Riecken, Oct 08 '20 at 09:37

Kusalananda · Answer 1 · 2020-10-08T10:58:07.243

Since you use $odi_cluster unquoted in the call to echo, the shell will split the variable's value on any character that also occur in $IFS (and then perform filename globbing on the generated words). Ordinarily, $IFS contains a space, a tab character, and a newline, but you've re-set it to be a comma.

If the variable's value is odi_server1,odi_server2 and $IFS contains a comma, this splitting results in the two words odi_server1 and odi_server2. These will be given to echo as two separate arguments and echo utility will output these with a separating space.

To avoid letting IFS have any effect on the output, prevent the shell from splitting the variable's value by quoting the expansion:

echo "$odi_cluster"

or

printf '%s\n' "$odi_cluster"

IFS=, read ...

This avoids setting IFS to a non-default value for the rest of the script.

Possibly also related:

Why is using a shell loop to process text considered bad practice?

Also note that the characters # and ! of the #!-line must be the very first characters of the file, and that you don't need to end each statement with a ; unless there are further statements on the same line.

How to output comma separated values using IFS="," in shell

1 Answers1