UNIX for Beginners Questions & Answers

Hi All,
I have 2 pipe delimited files viz., file_old and file_new. I'm trying to compare these 2 files, and extract all the different rows between them into a new_file.

Code:

comm -3 < sort file_old < sort file_new > new_file

I am getting the below error:

Code:

-ksh: sort: cannot open [No such file or directory]

But if I do as below, it is successfully giving me the difference.

Code:

sort file_old > file1
sort file_new > file2
comm -3 file1 file2 > file3

Can you please help me understand why the first approach resulting in an error?

Thank you.

PS: I did search the forum before posting this thread but no luck

Moderator's Comments:

Please use CODE tags as required by forum rules!

I think you need to deploy ksh's "process substitution":

Code:

comm -3 <(sort file_old) <(sort file_new) > new_file

It displayed syntax error if I include brackets "()".

Code:

comm -3 < (sort file1) < (sort file3) > file3
-ksh: syntax error: `(' unexpected

comm -3 < (sort file1) < (sort file3) > (file3)
-ksh: syntax error: `(' unexpected

That's NOT what I posted!

To expand a little bit on what RudiC already said...

If you're trying to perform process substitution, there can't be any space between the redirection operator and the (utility [argument...]).

To avoid confusion in the future, note that ( and ) are called parentheses; brackets are [ and ] and braces are { and }. Brackets, braces, and parentheses all have distinct meaning in the shell command language; they are not interchangeable.

Note also that process substitution is a fairly new feature in ksh and is not available in all versions of the Korn shell. And, you haven't told us which version of ksh you're using. It was not available in any version of ksh before 1993 and was not in the early version of ksh93. It is in version 93u+ from August 1, 2012, but I am not sure which version first included process substitution.

Thank you Don for explaining in so much detail. Please see below, getting same error even after removing the spaces between "<"/">" and following command.

Code:

$ ksh --v
  version         sh (AT&T Research) 93u+ 2012-08-01
$ comm -3 <sort file_old <sort file_new >new_file
-ksh: sort: cannot open [No such file or directory]

---------- Post updated at 04:19 PM ---------- Previous update was at 04:16 PM ----------

It didn't work with parenthesis also.

Code:

$ comm -3 <(sort file_old) <(sort file_new) >new_file
-ksh: sort: cannot open [No such file or directory]

Are you pointing to the correct directory?
Does that directory exist?
Are 'file_old' and 'file_new' in the current directory?
Do both in fact exist?