linux - Regex to add a character at the beginning of a particular line in a file -

i have file having n number of lines want find 1 line , edit without printing file contents on screen. file dynamically created can't count spaces , all. want use regex this.

my file is:

password               requisite    pam_pwquality.so retry=3 password               requisite    pam_passwdqc.so password               requisite    pam_deny.so 

and want make as:

#password               requisite    pam_pwquality.so retry=3 password               requisite    pam_passwdqc.so password               requisite    pam_deny.so 

i tried these:

sed 's/password[ \t]+requisite[ \t]+pam_pwquality.so/s/^/#/' test1  x='/password[ \t]+requisite[ \t]+pam_pwquality.so/'  sed -i -e "s/\($x\)/#\1/" test1  re="^[password][[ :blank: ]]*[requisite][[ :blank:]]*[pam_pwquality.so][[ :blank:]]*[retry=3]" 

but no changes in file.

i use awk:

awk '$1=="password" && $2=="requisite" && $3=="pam_deny.so" {        $0="#"$0      }1' file 

awk splits line fields separated 1 or more whitespace characters (which includes tabs). makes simple check content of individual fields.

with gawk can change file in place:

gawk -i inplace '$1=="password" && $2=="requisite" && $3=="pam_deny.so" {      $0="#"$0 }1' file