How To Edit a File Through Bash Script

rabir · 04-19-2012, 11:52 AM

Dear All

I wanna try to write a bash script that automatically configure my linux server. But i need to know the commands that "disable all lines of that file or specific file that i mension it." as well as want to input my desired lies through bash commands.

As cat>> myfile can append my file but it does not work in bash.

Help anyone.

kbp · 04-19-2012, 12:08 PM

For that specific requirement I'd probably use:

Code:

perl -ni -e 'print unless /<regex>/' /path/to/file

For editing a specific line in a file:

Code:

perl -pi -e 's/<regex>/<replacement>/g' /path/to/file

To create a file:

Code:

cat <<EOF > /path/to/file
content
$myvar
content
EOF

To create a file without shell interpretation (handy when generating a script):

Code:

cat <<'EOF' > /path/to/file
content
PATH=$HOME/bin:$PATH
content
EOF

dayid · 04-19-2012, 12:09 PM

Quote:

Originally Posted by rabir

Dear All

I wanna try to write a bash script that automatically configure my linux server. But i need to know the commands that "disable all lines of that file or specific file that i mension it." as well as want to input my desired lies through bash commands.

To "disable all lines" you would simple comment out the lines (or blank them)

To blank the file, simple:

Code:

: > file

To comment out all lines:

Code:

sed -e 's/^/#/g' file > tmp && mv tmp file

To add your own text to something you most likely want "echo" along with "read":

Code:

echo -n "What is your hostname? "
read ANSWER
echo "Hostname: $ANSWER" >> file

That's the very basics. For anything more complicated you'll need to give more context to work with.

rabir · 04-24-2012, 04:09 AM

Thank you very much "dayid" for your help.

problem # 1
the problem is that -->in a file first i want to search specific line & make it disable
as grep -n "error" /etc/named.conf
then
change according to the result.

Problem # 2
How do i get my Lan card hardware address ?

Problem # 3
suppoese i take a value from user as "read variable1" & have to reverse it & as well as truncate according to my choice & again use it as a string

thanks again for help

grail · 04-24-2012, 04:37 AM

Show us what you have tried regarding each of the questions and we can help guide you the answer.

For your first question, have a look at each of the sed answers provided already.