sed append with variable

Drexel

Hi all,

hopefully someone can help me with this. No solution on the net has worked for me. Its just something simple im missing.

I want to add a line to a text file after a certain regex. what I have is

sed ' 
/dev/ a\ 
192.168.52.166  host ' ./hosts.txt

I want to insert 192.168.52.166 host after the line with 'dev' in it. Its fine like this but if I need the ip as a variable.

ipAddress="192.168.52.166  host"
sed ' 
/dev/ a\ 
$ipAddress ' ./hosts.txt

It always uses $ipAddress instead of the value. If I put the whole thing in double quotes I get a sed error. Ive tried loads of different combos of ' ' and " " and I still can get it to use the variable value. Any help would be great

moycullen14

jonny666 wrote: »

Hi all,

hopefully someone can help me with this. No solution on the net has worked for me. Its just something simple im missing.

I want to add a line to a text file after a certain regex. what I have is

sed ' 
/dev/ a\ 
192.168.52.166  host ' ./hosts.txt

I want to insert 192.168.52.166 host after the line with 'dev' in it. Its fine like this but if I need the ip as a variable.

ipAddress="192.168.52.166  host"
sed ' 
/dev/ a\ 
$ipAddress ' ./hosts.txt

It always uses $ipAddress instead of the value. If I put the whole thing in double quotes I get a sed error. Ive tried loads of different combos of ' ' and " " and I still can get it to use the variable value. Any help would be great

ipAddress="192.168.52.166  host"
sed "
/dev/ a\ 
$ipAddress " ./hosts.txt

replace ' with ". Within " variables are expanded but not filename wildcards. Within ' neither are.

Drexel

moycullen14 wrote: »

ipAddress="192.168.52.166  host"
sed "
/dev/ a\ 
$ipAddress " ./hosts.txt

replace ' with ". Within " variables are expanded but not filename wildcards. Within ' neither are.

Ive tried it with the double quotes and its garbled. I escaped the \ after the a and it just removed all txt form the file. strange. Cant for the life of me figure this out. Running Solaris 10 if that helps

azzeretti

jonny666 wrote: »

Ive tried it with the double quotes and its garbled. I escaped the \ after the a and it just removed all txt form the file. strange. Cant for the life of me figure this out. Running Solaris 10 if that helps

Not sure if I am missing something here but this is an handy online, this works for me anyway:

ip=" 127.0.0.1 host"; sed "/dev/ s/$/$ip/" ./host.txt

EDIT: Not sure if you meant you want to append the value to the end of the matched line or add a new line under the matched line. This is the former, just add "\n" at the start of $ip to add a new line.

Fenster

You've factored your code wrong. Two things are going on:

1. sed hates variables being used in a regex string (it turns them null, although I've never discovered why), and laughs at your puny attempts to use one. You can do this if you want, through sheer bloody-minded stubbornness (I have), but it isn't easy.
2. "$foo" and '$foo" are two different things. "$foo" is partially quoted, which means that some characters (~!./$.., etc) have a special meaning to the interpreter. '$foo' is fully quoted, which means that all characters are interpreted as literal characters with no special meaning attached by the interpreter.
   
   "$ipAddress" is a partially-quoted variable.
   '$ipAddress' is just is just a dollar sign and some other sundry characters.
   
   Read this for more information on quoting.

Two Three ways you can approach the problem:

[LIST=2]
[*]Treat the entire sed command as a variable, add it to an array, and loop through the array to execute the given sed commands.
[*]Escape the variable in the manner as given:

[mark][~] # touch hello.txt
[mark][~] # echo "hello friend" > hello.txt 
[mark][~] # bye="goodbye"
[mark][~] # cat hello.txt | sed -e "s/hello/"$bye"/"
goodbye friend

[*]Instead of append, try the newline ("\n") character:

[mark][~] # cat hello.txt | sed -e 's/hello/goodbye\nnew line\n/g;s/ //g'
goodbye
newline
friend

[/LIST]