sed formatting query2

Shell Programming and Scripting
1

i wish to remove "#" characters and replace them with a single # character. how to do that?
ex if the file is like

####aasd
##pqr
###pqr
#qwert

output shud be

#aasd
#pqr
#pqr
#qwert

plz hlp

2 
sed 's/##*/#/g' filename
3 
sed 's/#\{1,\}/#/g' file
4

Hi.

With some versions of sed you can use extended regular expressions, which can make the often inscrutable sed scripts slightly easier to read. Either as shown here or with -r:

#!/bin/sh

# @(#) s1       Demonstrate extended regular expressions in sed.

FILE=${1-data1}

sed --regexp-extended 's/#+/#/g' $FILE

Producing on your data in data1:

% ./s1
#aasd
#pqr
#pqr
#qwert

cheers, drl

5 
tr -s '#' < filename