[SOLVED] edit file using echo command

sachin.davra · 01-15-2014, 01:05 AM

i wanna edit a file using echo command.
suppose i wanna edit ntp.conf file and i wanna put # in front of some consicutive lines and wanna edit some line.
let say i wanna edit

Code:

server ipaddress

to

Code:

server some_other_ipaddress

jdkaye · 01-15-2014, 01:13 AM

Why do you need to use the echo command? Wouldn't it be simpler to use a terminal editor like emacs or nano? A command like this should do the job.

Code:

sudo nano /etc/ntp.conf

Have fun.
jdk

evo2 · 01-15-2014, 01:18 AM

Hi,

IMHO, echo is not the tool for the job. You can rewrite the file using echo but you can't really edit it. Can you explain why you want to use echo in this way?

Evo2.

PS. Best use "want to" instead of "wanna". It's not actually a word and comes across as whining - especially when used repeatedly.

dob12460 · 01-15-2014, 01:20 AM

I'm no expert, but echo is not an editor.

Have you tried using sed?

sed -i -e s/ipaddress/otheripaddress/g <filename>

sachin.davra · 01-15-2014, 01:21 AM

Quote:

Originally Posted by evo2

Hi,

IMHO, echo is not the tool for the job. You can rewrite the file using echo but you can't really edit it. Can you explain why you want to use echo in this way?

Evo2.

PS. Best use "want to" instead of "wanna". It's not actually a word and comes across as whining - especially when used repeatedly.

Actually i wanna write post script in kickstart file and there i wanna edit ntp.conf file and wanna write our ntp server ip in server directive and i wanna comment other server directive. how this can be achived using post script in kickstart?

evo2 · 01-15-2014, 01:35 AM

Hi,

sorry I'm not familiar with "post script". Can you use sed as suggested by dob12460?

Evo2.

PS. I was not joking about using "wanna".

dob12460 · 01-15-2014, 01:48 AM

If you're referring to the %post section of a .ks file you can use sed, as I mentioned.

And as evo2 has mentioned twice, it is best not to use "wanna" repeatedly. It comes across very poorly. Definitely recommend using "want to".

David

sachin.davra · 01-15-2014, 02:11 AM

Quote:

Originally Posted by dob12460

If you're referring to the %post section of a .ks file you can use sed, as I mentioned.

And as evo2 has mentioned twice, it is best not to use "wanna" repeatedly. It comes across very poorly. Definitely recommend using "want to".

David

but i don't know how to use sed. could you give me any suggestion.

jdkaye · 01-15-2014, 02:18 AM

Quote:

Originally Posted by sachin.davra

but i don't know how to use sed. could you give me any suggestion.

Try typing this command in a terminal window:

Code:

man sed

That should get you started.
jdk

sachin.davra · 01-15-2014, 02:22 AM

Quote:

Originally Posted by jdkaye

Try typing this command in a terminal window:

Code:

man sed

That should get you started.
jdk

Thanks guys for helping me out.

evo2 · 01-15-2014, 02:23 AM

Hi,

Quote:

Originally Posted by sachin.davra

but i don't know how to use sed. could you give me any suggestion.

see post #4 above. Also search online for something like "basic sed tutorial". Ask back here if you get stuck.

Evo2.

rknichols · 01-15-2014, 02:55 PM

To answer the original question, yes it is possible to edit a file using nothing more than the shell's builtin read and echo commands together with the shell's ability to test and modify variables. At its most basic:

Code:

IFS=
while read -r Line; do
    case "$Line" in
    "server ipaddress")
        echo "server otheripaddress";;
    *)
        echo "$Line";;
    esac
done <file >file.new
while read -r Line; do
    echo "$Line"
done <file.new >file

I actually had to do something like that a long time ago in a SunOS standalone shell when a bad /etc/fstab left me with nothing but shell builtins to work with.

sachin.davra · 01-15-2014, 11:45 PM

Quote:

Originally Posted by rknichols

To answer the original question, yes it is possible to edit a file using nothing more than the shell's builtin read and echo commands together with the shell's ability to test and modify variables. At its most basic:

Code:

IFS=
while read -r Line; do
    case "$Line" in
    "server ipaddress")
        echo "server otheripaddress";;
    *)
        echo "$Line";;
    esac
done <file >file.new
while read -r Line; do
    echo "$Line"
done <file.new >file

I actually had to do something like that a long time ago in a SunOS standalone shell when a bad /etc/fstab left me with nothing but shell builtins to work with.

Thanks for giving the answer of my original question even i marked it as solved.

you have written a good script but i am not good at writing these kind of scripts. could you please gimme a link from where i can learn about this. because i am not able to understand most of the things in the script.

chrism01 · 01-16-2014, 03:01 AM

Learn bash from these links
http://rute.2038bug.com/index.html.gz
http://tldp.org/LDP/Bash-Beginners-G...tml/index.html
http://www.tldp.org/LDP/abs/html/

In the same vein as previous comments, use proper English ie use 'give me' not 'gimme' ... it really does come across very poorly

sgosnell · 01-17-2014, 09:39 AM

Many posters here do not have English as their native language. They do their best to communicate using English, and usually better than most native English speakers would do in another language. Disparaging the English usage of posters is not, IMO, a good thing.