在文件中查找字符串并使用bash和sed添加内容

Question

I'm trying to add a string with a bunch of filenames (which include directory slashes) to a file after a specific search string.

I've created my input text like this:

for f in /tmp/et/*.rules; do 
    #STRING+=`basename "$f"`$'\n'; 
    STRING+=$'include $RULE_PATH/et/'`basename "$f"`$'\n'
done

Which makes $STRING equal:

include $RULE_PATH/et/emerging-activex.rules
include $RULE_PATH/et/emerging-attack_response.rules
include $RULE_PATH/et/emerging-botcc.portgrouped.rules
include $RULE_PATH/et/emerging-botcc.rules
include $RULE_PATH/et/emerging-chat.rules
include $RULE_PATH/et/emerging-ciarmy.rules
include $RULE_PATH/et/emerging-compromised.rules
include $RULE_PATH/et/emerging-current_events.rules
include $RULE_PATH/et/emerging-deleted.rules
include $RULE_PATH/et/emerging-dns.rules

and my sed command to add the $STRING content looks like this:

sed -i.bak 's!^#EMERGING\ THREATS\ RULESET.*$!& \n'"$STRING"'!' snort.conf

this is looking for the text #EMERGING THREATS RULESET and adding $STRING on a new line after the matched text.

I had to change the default sed delimiters to something else because the default / were conflicting with the directory paths in my $STRING . Now, the problem is that I'm getting an error from sed stating:

sed: -e expression #1, char 82: unterminated `s' command

I know this has gotta be a simple problem with string manipulation or something regarding the quotes, but I've tried lots of combinations here and can't figure it out...

Answer 1

Ok use this approach:

#!/bin/bash
> _tmp
for f in /tmp/et/*.rules; do 
    echo $'include $RULE_PATH/et/'`basename "$f"`$'\n' >> _tmp
done

sed -i.bak '/^#EMERGING THREATS RULESET/r _tmp' snort.conf

Which basically stores your output in a temporary file and uses that temporary file to replace content in sed command after your search pattern.

Answer 2

You are using incorrect delimiter:

 
 
 
  
  sed -i.bak 's!^#EMERGING\\ THREATS\\ RULESET.*$/& \\n'"$STRING"'!' snort.conf ^ | ---------------------------------------------
 
  

So it seems your issue is unescaped newline. You cannot have an unescaped newline in sed replacement text ( $STRING in your example). sed scripting uses the newline just like the shell does, to terminate a command.

If you need a newline in the replacement text, you need to precede it with a backslash. Alternatively, if you're using gnu sed and do not care about portability to other sed implementations, you can replace a newline with a \\n , in the replacement text (all posix-compliant seds allow this in the regular expression, but not in the replacement as it is a gnu extension). Since your embedded newline is in a variable, this approach will not work for you.

So you can either do as @anubhava has shown in his answer, or alternatively use an awk solution:

awk -v patt="$STRING" '/^#EMERGING THREATS RULESET/{print $0;print patt;next}1' snort.conf >tmp && mv tmp snort.conf

Not that this would need GNU awk .