inserting some text into a file using 'awk' command

eliote · 10-20-2010, 03:32 AM

hi all,

I'm gonna replace my machine's ip address and hostname using awk command. the pattern of the file is like the following...

ip address="192.168.1.100"

the script must ask the ip address from the user and replace it with the ip address in the quotation.
any suggestion.

Jerry Mcguire · 10-20-2010, 04:45 AM

why awk?

Code:

#!/bin/sh

read -p "New IP address" newip

{
grep -v "^ip address=" $your_file
echo "ip address=\"$newip\""
} >$new_file

exit 0

Is this what you need?

grail · 10-20-2010, 05:08 AM

I agree that awk would probably not be my first choice here, but this would do what you want:

Code:

#!/usr/bin/awk -f

BEGIN{
	print "Please enter new ip address"
	getline newip < "-"
}

/ip/{

	sub(/"[^"]*/,"\""newip)
}	
1

The downside with awk is that you need to output this to a temp file and then delete the old file and rename temp.

crts · 10-20-2010, 06:45 AM

Hi,

does it have to be awk? If not here is another alternative.

Code:

#!/bin/bash

read -p "New IP address" newip
sed -ri 's/^(ip address=).*/\1"'$newip'"/' file

grail · 10-20-2010, 07:59 AM

I too like crts' solution and here is a slight variation to do away with excess quoting:

Code:

#!/bin/bash

read -p "New IP address" newip
sed -i "/ip/s/[0-9].*[0-9]/$newip/" file

crts · 10-20-2010, 08:12 AM

@grail: nice!

Let's just anchor the 'ip'

Code:

#!/bin/bash

read -p "New IP address: " newip
sed -i "/^ip address=/s/[0-9].*[0-9]/$newip/" file

so that 'my 12th artificial hip' won't get changed

grail · 10-20-2010, 08:31 AM

Yeah I wasn't sure where in the line it was

ghostdog74 · 10-20-2010, 11:27 AM

Code:

awk 'BEGIN{
 print "Please enter new ip address"
 getline newip < "-"
 OFS=FS="="
}
/^ip address/{ $2="\042"newip"\042"}
{ a[++d]=$0 }
END{
  for(i=1;i<=d;i++){ print a[i] > "TEMP" }
  cmd="mv TEMP " FILENAME
  system(cmd)
}' file

eliote · 10-25-2010, 12:56 AM

Quote:

Originally Posted by crts

@grail: nice!

Let's just anchor the 'ip'

Code:

#!/bin/bash

read -p "New IP address: " newip
sed -i "/^ip address=/s/[0-9].*[0-9]/$newip/" file

so that 'my 12th artificial hip' won't get changed

thanks a lot crts.
but could you please describe what /s/[0-9].*[0-9]/ stands for!?
i don' understand what is that for.

crts · 10-25-2010, 01:09 AM

Quote:

Originally Posted by eliote

thanks a lot crts.
but could you please describe what /s/[0-9].*[0-9]/ stands for!?
i don' understand what is that for.

Code:

s/[0-9].*[0-9]/$newip/

is sed's substitution command. It works in the manner

Code:

s/pattern/replacement/

[0-9] is called a character class. It stands for any digit from 0..9.
The '.' stand for any character and the asterisk is a quantifer to the previous expression. So '.*' stands for any amount of any characters. So in the processed line anything that is enclosed between two digits will be replaced with $newip.

eliote · 10-25-2010, 03:46 AM

Quote:

Originally Posted by crts

Code:

s/[0-9].*[0-9]/$newip/

is sed's substitution command. It works in the manner

Code:

s/pattern/replacement/

[0-9] is called a character class. It stands for any digit from 0..9.
The '.' stand for any character and the asterisk is a quantifer to the previous expression. So '.*' stands for any amount of any characters. So in the processed line anything that is enclosed between two digits will be replaced with $newip.

thank you so mucn crts, that worked

but what if i want to insert a range of IP address like this;

ip address="192.168.1.10/24"

I've tried to add '/24' at the end of the read parameter ($new ip), but that does'n work.

grail · 10-25-2010, 04:58 AM

Quote:

I've tried to add '/24' at the end of the read parameter ($new ip), but that does'n work.

Please explain what you mean here?

I did the following which works fine:

Code:

read -p "Enter new ip: " newip

echo "$newip"

Running this:

Code:

$Enter new ip: 1.2.3.4/24
1.2.3.4/24

eliote · 10-25-2010, 05:51 AM

Quote:

Originally Posted by grail

Please explain what you mean here?

I did the following which works fine:

Code:

read -p "Enter new ip: " newip

echo "$newip"

Running this:

Code:

$Enter new ip: 1.2.3.4/24
1.2.3.4/24

want to add this replacement by script:
ip address="192.168.1.10/24"
----------------------------------------
and i used this command in my script
read -p "IP address:" newip
sed -ri 's/^(ip address=).*/\1"'newip/24'"/' filename

that didn't work for me grail, any idea?

crts · 10-25-2010, 06:02 AM

Quote:

Originally Posted by eliote

want to add this replacement by script:
ip address="192.168.1.10/24"
----------------------------------------
and i used this command in my script
read -p "IP address:" newip
sed -ri 's/^(ip address=).*/\1"'newip/24'"/' filename

that didn't work for me grail, any idea?

change your sed statement to

Code:

sed -ri "/^ip address=/ s|[0-9].*[0-9]|$newip|" file

eliote · 10-26-2010, 12:58 AM

Quote:

Originally Posted by crts

change your sed statement to

Code:

sed -ri "/^ip address=/ s|[0-9].*[0-9]|$newip|" file

that didn't work crts!
maybe you could help me more interactively...
have you got yahoo ID?!