Shell Programming and Scripting

Hi there.

I'm facing a strange & an intriguing behaviour with sed while replacing the tab character with a space reading from a file. It randomly works sometimes but mostly doesn't work.

Below is what's happening-

<tab> here is the actual literal tab.

user1> cat temp2
1<tab>2<tab>3 4 5<tab>6
<tab>1 2<tab>3<tab><tab>4<tab>5 6

user1> sed 's/<tab>/ /g' temp2 ------> Did NOT work here
1<tab>2<tab>3 4 5<tab>6
<tab>1 2<tab>3<tab><tab>4<tab>5 6

user1> sed 's/<tab>/ /g' temp2 ------> Worked this time
1 2 3 4 5 6
1 2 3 4 5 6

user1> sed 's/<tab>/ /g' temp2 ------> Worked again
1 2 3 4 5 6
1 2 3 4 5 6

user1> sed 's/<tab>/ /g' temp2 ------> Did NOT work here
1<tab>2<tab>3 4 5<tab>6
<tab>1 2<tab>3<tab><tab>4<tab>5 6

user1> sed 's/<tab>/ /g' temp2 ------> Did NOT work here
1<tab>2<tab>3 4 5<tab>6
<tab>1 2<tab>3<tab><tab>4<tab>5 6

user1> sed 's/<tab>/ /g' temp2 ------> Did NOT work here
1<tab>2<tab>3 4 5<tab>6
<tab>1 2<tab>3<tab><tab>4<tab>5 6


I did not change the temp2 file in any manner whatsoever throughout the above steps.

Anyone got any idea about this???

Thanks,
Deepak.D

Please put [code] and [/code] tags around your data so the forum doesn't change the format.

I'd also suggest you use /usr/bin/sed on command line to avoid any possibility on aliases or PATH changes causing you to use a non-standard sed.

Also pipe output to od -c to ensure we see non printables eg:

Code:

$ od -c temp2
0000000    1  \t   2  \t   3       4       5  \t   6  \n  \t   1       2
0000020   \t   3  \t  \t   4  \t   5       6  \n
0000032
$ /usr/bin/sed "s/$(printf "\t")/ /g" temp2 | od -c
0000000    1       2       3       4       5       6  \n       1       2
0000020        3           4       5       6  \n
0000032

Thank you Chubler_XL, your suggestion works & is also consistent.

Code:

user1> sed "s/$(printf "\t")/ /g" temp2
1 2 3 4   5 6
 1  2 3 4  5 6
1 2 3 4   5 6
 1  2 3 4  5 6