Bash & Sort

[mfreeze]

Does anyone have any any experience with the following situation?

I am using BASH and I am trying to sort a file using the command-line sort command. I have done this on Fiesty and on Dapper and get the same results. Consider the following tab-delimited file (test.txt)(Tabs indicated as [tab] for readability):


PSL [tab] 99887766 [tab] Bill Blue [tab] 33445566
PSL [tab] 99887766 [tab] Bill Blue [tab] 33445566
PFF [tab] 43305900 [tab] Yasmine Yellow [tab] 12097847
PAB [tab] 34567901 [tab] Gina Gold [tab] 21309854
PXX [tab] 12345765 [tab] Ralph Red [tab] 67480194
PTR [tab] 87458762 [tab] Paul Purple [tab] 78409710
If I perform the sort:


sort -t \t -k 1 test.txt

I correctly get:


PAB 34567901 Gina Gold 21309854
PFF 43305900 Yasmine Yellow 12097847
PSL 99887766 Bill Blue 33445566
PSL 99887766 Bill Blue 33445566
PTR 87458762 Paul Purple 78409710
PXX 12345765 Ralph Red 67480194

If I sort:


sort -r -t \t -k 1 test.txt


PXX 12345765 Ralph Red 67480194
PTR 87458762 Paul Purple 78409710
PSL 99887766 Bill Blue 33445566
PSL 99887766 Bill Blue 33445566
PFF 43305900 Yasmine Yellow 12097847
PAB 34567901 Gina Gold 21309854

However, If I try to sort the 4th field with:


sort -t \t -k 4 test.txt
or
sort -n -t \t -k 4 test.txt
or
sort -n -t \t -k 4,4 test.txt

I get


PAB 34567901 Gina Gold 21309854
PFF 43305900 Yasmine Yellow 12097847
PSL 99887766 Bill Blue 33445566
PSL 99887766 Bill Blue 33445566
PTR 87458762 Paul Purple 78409710
PXX 12345765 Ralph Red 67480194

No matter what I do, it will not sort the file by the 4th column.

However, with this same file, this operation does work correctly on my OpenBSD box. (Or should I say that I can accurately sort by the 4th field on my OpenBSD box.)

What can the problem be on Linux?

Thanks,
Mark.

[Lux Perpetua]

The problem is that \t evaluates to t in bash. The trick is getting a literal tab character onto your command line. bash and readline don't make this very easy in my opinion. (Any naive attempt to press the tab character will trigger the command-completion feature.) The way to do it is to press Control-V before you press Tab. Control-V causes the next key you press to be interpreted literally and inserted on the command line. Make sure you enclose your tab character in quotes, or bash will treat it as blank space and skip it!

edit: Alternatively, you can use a shell other than bash, one that interprets the Tab key literally.

[ghostdog74]

sort -k4 file

[mfreeze]

It works! I bow inthe presence of your supreme knowledge.

Why does this work correctly in the Bash shell on OpenBSD, but not in the Bash shell on Linux? I have a friend who observed the same behavior on Fedora.

Again, thanks for the help.

Regards,
Mark.

[Lux Perpetua]

Can you post the output of bash --version on your OpenBSD box?

edit: I just found a cleaner way to solve your problem:
sort -n -t $'\t' -k 4 test.txt

See http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_03_03.html, the section on ANSI-C quoting.