sed Tip: Delete All Blank White Spaces

by nixCraft on June 9, 2013 · 5 comments· LAST UPDATED June 9, 2013

in BASH Shell, Linux, Perl, UNIX

I have a text file as follows:

   foo
   bar
  foobar 

How can I delete all leading and/or trailing blank spaces, tab from each line using sed command?

Tutorial details
Difficulty	Easy (rss)
Root privileges	No
Requirements	sed/awk/perl
Estimated completion time	2 minutes

You can use sed command to delete all white (blank) spaces in a text file. You can also use other text processing utilities such as:

1. Perl.
2. Python.
3. Awk and friends.

Perl example

The syntax is:

perl -lape 's/\s+//sg' input > output

Sample outputs:

foo
bar
foobar

Or use -pie syntax to update file:

 
cat input
perl -lapi -e 's/\s+|^\n//sg'  input
cat input
 

See perl man page for more information.

Sed example

The syntax is:

sed -e 's/^[ \t]*//' -e 's/[ \t]*$//' input > output

OR updated file in a single go with the -i option:

sed -i -e 's/^[ \t]*//' -e 's/[ \t]*$//' input

See sed command man page for more information.

Awk example

The syntax is

awk '{$1=$1}{ print }' input > output

You can also use gsub() substring matching the regular expression function. See awk man page for more information.

http://www.cyberciti.biz/faq/sed-tip-delete-all-blank-white-spaces/