Bash - find a keyword in a file and delete its line

bash sed grep command-line-interface replace

32,968

Solution 1

sed -i ".bak" '/culpa/d' test.txt

The above will delete lines containing culpa in test.txt. It will create a backup of the original (named test.txt.bak) and will modify the original file in-place.

Solution 2

Pipe it to another file, not the same one that you're reading from, and be careful with the useless use of cat.

grep -v "$KEYWORD" /etc/hosts > newfile

Apart from the fine answer given regarding sed, you can also use Perl and a little improved regex to solve this:

perl -pi.old -e 's/.*\sdomain\.com\s*\n//' file

Notice I'm considering domain.com will be isolated by space characters (tabs or spaces, and so on), and that nothing but zero or more spaces will appear after it until the newline. Similarly to -i in sed,
-i.old in perl sets the $^I variable, and your original file will receive the changes while a copy will be kept under the old name and a .old appended.

Solution 3

If you want to only delete last line of your example file

sed -i '/[[:space:]]\+domain\.com/d' test.txt

32,968

Author by

Roger

Be the change you want in the world! - M. Gandhi

Updated on July 10, 2022

Comments

Roger almost 2 years
I'd like to give a keyword, find the line where this keyword aṕpears in a file and erase the entire line.

This is what I got but it is not working as it should:
```
KEYWORD='domain.com'
cat /etc/hosts | grep -v "$KEYWORD" > /etc/hosts
```
UPDATE

This is what worked for me:

sed -i_bak -e '/domain\.com/d' /etc/hosts

However, as I had two lines with "domain.com", is there a way to tell sed to erase only the line where the exact keyword "domain.com" appears

This is the original content of /etc/hosts:
```
127.0.0.1       localhost       localhost.localdomain
222.111.22.222      hvn.domain.com
222.111.22.222      domain.com
```
Here's how it end up after the command sed -i_bak -e '/domain\.com/d' /etc/hosts:
```
127.0.0.1       localhost       localhost.localdomain
```
I tried sed -i_bak -e '/\<namourphoto\.com\.br\>/d' ~/Desktop/hosts but it didn't work.

CONCLUSION

This is the code I came up with (based on the help the fine folks have given me):
```
D=domain.com
DOMAIN=`echo "$D" | sed 's/\./\\\\./g'`
sed -i_bak -e "/[\t]$DOMAIN/d" /etc/hosts
```
Note that:
- I am counting that there is always a tab before the domain to be erased
- I am automatically escaping the dots of the domain name.
- duri over 12 years
  
  Please also note that dot has special meaning in regexps so domain.com will also match domainxcom.net. You should escape the dot.
- Roger over 12 years
  
  Must I escape dots even when between ''?
- duri over 12 years
  
  Yes, you do. Try echo abc | grep 'a.c', the output will be abc.
- Roger over 12 years
  
  I wrote a code (above) to do escape the dots automatically
- chad over 12 years
  
  add a space to the [\t] part, since /etc/hosts is whitespace separated.
- Roger over 12 years
  
  How can I write the regex to choose from space or tab?
- Roger over 12 years
  
  What if I let the option of a space or a tab? (In my case, it's a tab). Would this be right? /[:space:\t]$DOMAIN/d
Roger over 12 years

Is there a way to edit in place with this approach or I always need to make another file in order to edit it?
sidyll over 12 years

@Roger, I updated the answer.
Roger over 12 years

Very elegant your code, thank you.
Roger over 12 years

My tests didn't work with the space among -i and .bak. But when I pu -i.bak it did work.
sidyll over 12 years

@Roger: De nada, e bonito cachorro. Será que essa área verde aí atrás é aqui em SP? :P
Roger over 12 years

origado, é um Akita. Sim, a paisagem é no Morro do Ouro, em Apiaí; conhece?
Adam Johns about 10 years

how do you do this while discarding the original without making backup? UPDATE: just made the ".bak" quote blank to answer my own question.
Luka over 7 years

in my case keyword is ipaddress with . and port : IS this right? sed -i "/$proxy[^0-9]/d" proxy.txt