bug#13301: patch to preserve field order in cut (original) (raw)

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From: Bob Proulx
Subject: bug#13301: patch to preserve field order in cut
Date: Fri, 28 Dec 2012 17:06:48 -0700
User-agent: Mutt/1.5.20 (2009-06-14)

severity 13301 wishlist thanks

Brad Cater wrote:

I found that echo "a,b,c" | cut -d"," -f1,2 gives the same result as echo "a,b,c" | cut -d"," -f2,1

This is because 'cut' has always behaved that way way back forty years for forever. So people like me don't consider it a bug. It is just the way it was written to work.

The GNU manual documents it this way:

The list elements can be repeated, can overlap, and can be specified in any order; but the selected input is written in the same order that it is read, and is written exactly once.

This means that it's necessary to use another process to re-order columns.

The standard solution is to use 'awk'. It also has a lot of years behind it.

$ echo "a,b,c" | awk -F, '{print$2,$1}' b a

Using awk also allows duplication of fields.

$ echo "a,b,c" | awk -F, '{print$2,$1,$2}' b a b

I have written a patch for cut.c ...

I have not looked at the patch but the barrier to adding new short options is pretty high. I will leave that for others to comment. Personally I don't think it is necessary since awk is already standard and therefore use of the feature is already available everywhere that you need it without any changes.

This issue is discussed periodically. Here are a few that I found with a quick search.

http://lists.gnu.org/archive/html/bug-coreutils/2005-06/msg00125.html http://lists.gnu.org/archive/html/bug-coreutils/2007-09/msg00020.html http://lists.gnu.org/archive/html/bug-coreutils/2007-09/msg00169.html

Bob