Trying to remove a # sign from a single line in a file. The line is currently

#/usr/bin/tvservice -o
if [[ '$grep tvservice /etc/rc.local' =~ ^# ]] ;
then sed -i '/^#.* tvservice /s/^#//' /etc/rc.local ;
else echo 1 fi

Trying to test if this command will work before I add it to a script. When I run it I get a > symbol and have to stop execution with Ctrl+C

Am I not passing a string to grep correctly or what? I'm fairly new to this.


I suggest you test without sed's -i flag first - or use a local copy of the rc.local file.

You don't need to test for the string's presence, but if you do, then the correct way to substitute grep's output would be "$(grep tvservice /etc/rc.local)" - the way you have written it tests the literal string $grep tvservice /etc/rc.local

However, a better way IMHO would be to grep for the whole pattern and use grep's exit status directly, avoiding the shell regex test altogether:

if grep -q '^#.*tvservice' /etc/rc.local; then 
  sed -i '/^#.*tvservice/ s/^#//' /etc/rc.local
  echo 1

(I removed the spaces around the pattern, since your sample text doesn't have them).

| improve this answer | |
  • Meh, just a minute faster than me... – Byte Commander Feb 24 '18 at 15:25
  • I ran the command in this form and am getting 2 as output and then nothing. It doesn't really exit the script properly, any clues ? if grep -q '^#/*tvservice' /etc/rc.local; then echo 1 sed -i '/^#.*tvservice/ s/^#//' /etc/rc.local else echo 2 sed -e '/tvservice/ s/^#*/#/' fi – Kylar Stern Feb 24 '18 at 19:29
  • This is the state of the file currently {code} #!/bin/sh -e # # rc.local # # This script is executed at the end of each multiuser runlevel. # Make sure that the script will "exit 0" on success or any other # value on error. # # In order to enable or disable this script just change the execution # bits. # # By default this script does nothing. #Disable HDMI #/usr/bin/tvservice -o exit 0 {code} – Kylar Stern Feb 24 '18 at 19:33
  • I saw for second sed I didn't give it a file to edit. Fixed it the command runs and exits out but I get the "2" as output still which means that it skips the "then" where it's supposed to remove the # from that line. – Kylar Stern Feb 24 '18 at 19:46

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