Alternate for sed -i in AIX

Shell Programming and Scripting
1

Experts,

At the moment I am working in AIX box where sed -i is not available.
My requirement is as below

Two files file1 and file2. file1 contains the IP address, its count. file2 contains the Hostname and its corresponding IP address. I would like get the IP address replaced with the apt Hostname in file1.

# cat file1
192.168.20.8    => 1
192.168.20.24   => 2
192.168.20.6    => 2
192.168.20.7    => 3
192.168.20.9    => 3
192.168.20.25   => 4
192.168.20.26   => 4
192.168.20.23   => 6

# cat file2
192.168.20.6    ser70
192.168.20.7    ser71
192.168.20.8    ser72
192.168.20.9    ser73
192.168.20.23   ser80
192.168.20.24   ser81
192.168.20.25   ser82
192.168.20.26   ser83

My code is of:

for i in `awk '{print $1}' file1`
	do
	svr=$(grep $i file2 | awk '{print $2}')
	sed -i "s/$i/$svr/" file1
done

Expected Output:

# cat file1
ser72    => 1
ser81   => 2
ser70    => 2
ser71    => 3
ser73    => 3
ser82   => 4
ser83   => 4
ser80   => 6

But unfortunately sed -i is not present in my AIX box, please shoot me an alternative. :slight_smile:
Also if the IP address is not found in file2, that row should be left untouched in file1.

2

Doubtless you can simplify the code further, i.e. by using awk to read both files and substitute the correct values. You would then write this to a temporary file and copy that over the original.

Otherwise, using ed is an easy way to begin with:

ed file1 << !
, s/$i/$svr/
w
q
!
1 Like
3

You could use use awk:

awk 'NR == FNR {
  iton[$1] = $2
  next
  }
($1 in iton && $1 = iton[$1]) || 1
  ' file2 file1 > _tmp_file_ &&
      mv -- _tmp_file_ file1

If the original order is not important and your shell supports process substitution (zsh, ksh93 and bash):

join <(sort file2) <(sort file1) -o1.2,2.2,2.3
1 Like
4

Thanks for the prompt response Scott
Is the below right ?

for i in `awk '{print $1}' file1`
	do
	svr=$(grep $i file2 | awk '{print $2}')
	ed file1 << EOD
		, s/$i/$svr/
		w
		q
	EOD
done
5

Only if the closing EOF is indented with a TAB (or nothing at all - it won't work if those are spaces before it).

A note to radoulov's solution (which is nice :)). Moving a temporary file over an existing file can be dangerous.

I did that once, and it caused no end of grief!

# ls -l rc.tcpip
-rwxrwxr-- 1 root system 6409 Aug 21 2009 rc.tcpip
 
# sed "s/change_this/to_this/" rc.tcpip > _tmp_rc_tcpip
# mv _tmp_rc_tcpip rc.tcpip
# ls -l rc.tcpip
-rw-r--r-- 1 root system 6406 Jan 7 2013 rc.tcpip

rc.tcpip won't get executed after a reboot. You can guess what happened next :slight_smile:

2 Likes
6

WOW!!

This works out, can you please explain the code.

7

Great point Scott!
sed's -i is far more sophisticated (if I recall correctly, it handles even extended acls).

To the OP: with this manual method you'll need to handle the file permissions/inode changes manually ...

8 
awk 'NR == FNR {
  # while reading the fist input file
  # store the names in an array
  # keyed by the IPs
  iton[$1] = $2
  next
  }
# if the IP has an associated name
# assign its value to $1
# otherwise just return the record
# 1 -> true -> print $0  
($1 in iton && $1 = iton[$1]) || 1
  ' file2 file1 > _tmp_file_ && 
      mv -- _tmp_file_ file1
1 Like