topic Re: Unalbe to remove "tab" character using "sed" in Operating System - Linux

Unalbe to remove "tab" character using "sed"

Raghu Chikkamenahalli — Wed, 13 Feb 2008 11:04:44 GMT

Hello,

Trying to remove a tab character using sed as follows.

sed 's/[ \t]*$//' file_name.txt

But it is not removing the tab space as expected. To remove the tab space, again ran the sed as follows.

sed 's/[ ]*$//' file_name.txt ( here insted of "\t" used the tab key .

Can anybody help to resolve this.

Regards,
Raghu.

Re: Unalbe to remove "tab" character using "sed"

James R. Ferguson — Wed, 13 Feb 2008 12:57:30 GMT

Hi:

Not all 'sed' variations support the '\t' escape character.

Using the TAB key as you did is valid.

Regards!

...JRF...

Re: Unable to remove "tab" character using "sed"

Dennis Handly — Sat, 17 Sep 2011 20:23:01 GMT

>JRF: Not all 'sed' variations support the '\t' escape character.

I don't see it documented in sed(1), or ed(1) or in regexp(5).

tr(1) mentions it takes \ then octal digits.

You could use a character class:
sed 's/[:space:]*$//' file_name.txt
Or:
$ sed -e "s/$(echo "[ \t]\c")\*$//" file_name.txt

Re: Unalbe to remove "tab" character using "sed"

James R. Ferguson — Thu, 14 Feb 2008 13:49:04 GMT

Hi (again):

> Dennis: >JRF: Not all 'sed' variations support the '\t' escape character.

> Dennis: I don't see it documented in sed(1), or ed(1) or in regexp(5).

My remark was based both on experience and on the reference "...that the only C-like backslash sequences that you can portably assume to be interpreted are \n and \\; in particular \t is not portable, and matches a `t' under most implementations of sed, rather than a tab character."

...from:

http://www.gnu.org/software/sed/manual/sed.html

I too thought about suggesting the '[:space:]' character class, but rejected that since the author specifically asked about the '\t' escape and not the more generalized "whitespace" (space, tab, etc.).

Regards!

...JRF...

Re: Unable to remove "tab" character using "sed"

Dennis Handly — Sat, 17 Sep 2011 20:24:03 GMT

>JFF: My remark was based both on experience and on the reference

My comment about the documentation was that it didn't mention allowing it.

>I too thought about suggesting the '[:space:]' character class,

I suggested it since the above RE had a space AND a tab, so why not go for broke. :-)

Re: Unalbe to remove "tab" character using "sed"

Raghu Chikkamenahalli — Fri, 15 Feb 2008 07:25:10 GMT

Hello JRF,
Thanks for addressing the problem. It helpmed to resolve the issue.
regards,
raghu.