Bash Scripting : edit output of a variable

Question

I read some data out of a file, used grep for the only two columns needed, and redirected the output into a variable.

My script looks like this:

#!/bin/bash
cat hosts.cfg | grep 'address\|host_name' | sed -e 's/\<address\>//g'  | while read line; do
        echo $line | sed 's/host_name//g' | sed -r 's/\s+//g' ;
done

The output looks something like this now:

Host1
xx.xx.xx.xx
Host2
xx.xx.xx.xx

The problem is that hosts and ips must be saved into an array, not a file!

Output must look like this:

Host1(tab)xx.xx.xx.xx

Host2(tab)xx.xx.xx.xx

What does hosts.cfg look like? There may be a simpler solution than your chains of sed commands. — chepner
– chepner, Commented Oct 14, 2013 at 16:30

Jan Hudec · Accepted Answer · 2013-10-14 08:12:24Z

1

You are looking for process substitution. $(command), or old-style in `s.

_{(sorry, the description of how it should work is not clear enough for me to show modified version of your code)}

answered Oct 14, 2013 at 8:12

Jan Hudec

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Jon Cairns · Accepted Answer · 2013-10-14 08:16:57Z

0

You can use awk:

echo $output | awk 'NR%2{printf $0"\t";next;}1'

To save any command output, wrap it in backticks, or the newer (but less backward compatible) $(command) style substitution. E.g.:

result=`echo $output | awk 'NR%2{printf $0"\t";next;}1'`

answered Oct 14, 2013 at 8:16

Jon Cairns

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2 Comments

Dan Cordos Over a year ago

It must be saved in memory, not just printed .

Dan Cordos Over a year ago

My code looks like this right now: ' cat hosts.cfg | grep 'address\|host_name' | sed -e 's/\<address\>//g' | while read line; do echo $line | sed 's/host_name//g' | sed -r 's/\s+//g' | awk 'NR%2{printf $0"\t";next;}1' ; done ' It returns this: Host1 xx.xx.xx.xx Host2 xx.xx.xx.xx . What I need, to list them on single line like this: Host1 xx.xx.xx.xx (newline) Host2 xx.xx.xx.xx .

micheal.yxd · Accepted Answer · 2013-10-14 08:46:20Z

0

using sed 'N;s/\n/\t/g'

change

Host1
xx.xx.xx.xx
Host2
xx.xx.xx.xx

to

Host1(tab)xx.xx.xx.xx
Host2(tab)xx.xx.xx.xx

answered Oct 14, 2013 at 8:46

micheal.yxd

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Comments

Ranjithkumar T · Accepted Answer · 2013-10-26 09:28:47Z

You can use "set" to get faster output

exg:

I have file best2,

 # cat best2
 Host1 xx.xx.xx.xx Host2 xx.xx.xx.xx

make a script called: tabcheck.sh

 # cat tabcheck.sh
 #!/bin/bash
 out=$(cat best2)
 set $out
 echo -e "$1\t$2\n$3\t$4"

 # ./tabcheck.sh
 Host1   xx.xx.xx.xx
 Host2   xx.xx.xx.xx

If you use shift command(Usually only nine command line arguments can be accessed using positional parameters. The shift command gives access to command line arguments greater than nine by shifting each of the arguments.) as well.

Thanks.

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