I am trying to find and replace a specific string within /etc/ssh/sshd_config.
#PermitRootLogin yes > PermitRootLogin no.
However I want to make sure I get almost any version of it (if that makes sense).
ex;
#PermitRootLogin yes
PermitRootLogin yes
#PermitRootLogin no
I am fairly new to bash, linux, unix etc and have really only been learning this stuff for the past 2 weeks so if possible, please explain to me like i'm brand new to linux/unix. Thank you in advance.
So far i've tried 2 thing so far and neither of them seem to do what I need.
sed -E 's/(#|^)PermitRootLogin(yes|no)/PermitRootLogin no/' FILENAME
and
sed -E 's/(#/|^/)PermitRootlogin(yes/|no/)/PermitRootLogin no/' FILENAME
I was expecting all the lines in the example above to be changed to;
PermitRootLogin no
PermitRootLogin no
PermitRootLogin no
This one's just missing a space
sed -E 's/(#|^)PermitRootLogin(yes|no)/PermitRootLogin no/' FILENAME
# ............................^
I would suggest
sed -E '/PermitRootLogin/ s/.*/PermitRootLogin no/' FILENAME
which means: for any line containing the string "PermitRootLogin", replace the entire line with "PermitRootLogin no"
This one
sed -E 's/(#/|^/)PermitRootlogin(yes/|no/)/PermitRootLogin no/' FILENAME
shows a bit of a misunderstanding of the role of the / character in sed.
/ is not a regex character, it's the delimiter for the s command to separate the regular expression, the replacement text, and the flags. See 3.3 The s Command in the sed manual.
With your shown samples, please try following awk code.
awk '/^#?PermitRootLogin/{print "PermitRootLogin no"}' Input_file
Explanation: Simple explanation would be, checking condition if line starts with #(keeping it optional) followed by PermitRootLogin then using printing PermitRootLogin followed by no as per requirement.
NOTE: In case you want to do inplace save the changes into same Input_file then run following: awk '/^#?PermitRootLogin/{print "PermitRootLogin no""}' Input_file > temp && mv temp Input_file
You may use this sed:
sed -E 's/^#?(PermitRootLogin) +.*/\1 no/' file
PermitRootLogin no
PermitRootLogin no
PermitRootLogin no
Where input file is like this:
cat file
#PermitRootLogin yes
PermitRootLogin yes
#PermitRootLogin no
Explanation:
^: Start#?: Match an optional #(PermitRootLogin) +: Match PermitRootLogin and capture in 1st group followed by 1+ space.*: Match anything till end of line/\1 no/: Replacement section to put value of capture group #1 followed by space and noTo save change inline into file use:
sed -i.bak -E 's/^#?(PermitRootLogin) +.*/\1 no/' file