Appending a line just after the matched pattern in sed not working

Question

My /etc/pam.d/system-auth-ac has the below auth parameters set:

auth        required      pam_env.so
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        required      pam_deny.so

I want to insert pam_tally2.so just after pam_env.so . So I want it to be:

auth        required      pam_env.so
auth        required      pam_tally2.so onerr=fail audit silent deny=5 unlock_time=900
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        required      pam_deny.so

The script that I'm using is :

#! /bin/bash

grep "pam_tally2" /etc/pam.d/system-auth-ac &> /dev/null
if [ $? -ne 0 ];
then
   sed -i '/^[]*account[]*required[]*pam_unix.so/aauth\trequired\tpam_tally2.so onerr=fail audit silent deny=5 unlock_time=900' /etc/pam.d/system-auth-ac
else
   sed -i 's/.*pam_tally2.*/auth\trequired\tpam_tally2.so onerr=fail audit silent deny=5 unlock_time=900/1' /etc/pam.d/system-auth-ac
fi

But it gives this error:

sed: -e expression #1, char 116: unterminated address regex

What am I doing wrong ?

Answer 1

You can use a command in gnu-sed:

sed -i.bak '/pam_env\.so$/a\
auth        required      pam_tally2.so onerr=fail audit silent deny=5 unlock_time=900
' /etc/pam.d/system-auth-ac

---

EDIT: Looking at your posted answer it seems this awk command will be more suitable for you than grep and 2 sed commands in if/else condition:

val='auth\trequired\tpam_tally2.so onerr=fail audit silent deny=5 unlock_time=900'
awk -v val="$val" '/^auth[[:blank:]]+required[[:blank:]]+pam_env\.so/ {
   print $0 RS val; next} /pam_tally2\.so/{next} 1' /etc/pam.d/system-auth-ac

auth        required      pam_env.so
uth         required      pam_tally2.so onerr=fail audit silent deny=5 unlock_time=900
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        required      pam_deny.so

Answer 2

You may use the below sed command.

sed 's/^auth[[:blank:]]\+required[[:blank:]]\+pam_env\.so/&\nauth        required      pam_tally2.so onerr=fail audit silent deny=5 unlock_time=900' file

Your regex fails because you're repeating an empty character class [] , zero or more times, which won't make any sense. So you need to change []* to [ ]* or <space>* to repeat an empty space character zero or ore times.

Answer 3

My Script actually should have been:

#! /bin/bash

grep "pam_tally2" /etc/pam.d/system-auth-ac &> /dev/null
if [ $? -ne 0 ];
then
   sed -i '/^[ ]*auth[ ]*required[ ]*pam_env.so/aauth\trequired\tpam_tally2.so onerr=fail audit silent deny=5 unlock_time=900' /etc/pam.d/system-auth-ac
else
   sed -i 's/.*pam_tally2.*/auth\trequired\tpam_tally2.so onerr=fail audit silent deny=5 unlock_time=900/1' /etc/pam.d/system-auth-ac
fi

Works fine!