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I have a rather large config file that has server short names in it like this:

[host 1]
host = server1

[host 2]
host = server2

[host 3]
host = server3

I need to replace all the server short names with the fq long names that will be outputted from a bash script I've already written, lookup.sh. Can I work some sed or awk magic to accomplish this task?

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    what have you tried to do? using sed is of course possible, but let us know what you tried to do before. Commented Mar 28, 2016 at 18:28
  • How do you call lookup.sh? lookup.sh <hostname>? Commented Mar 28, 2016 at 19:39
  • "lookup.sh server1" will output server1.server.domain.com, of course this function could be added to the main search and replace script instead of calling it out. Commented Mar 28, 2016 at 20:00

1 Answer 1

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Your question implied the use of sed or awk, but you didn't explicitly rule out perl 😉

#!/usr/bin/perl
while (<>)
{
    if (/^host = (.+)/) {
        print "host = " . `./lookup.sh $1`;
    }
    else { 
        print;
    }
}

Upon further reflection, the same could be done in awk as follows:

#!/bin/bash

INFILE=$1

awk 'BEGIN { FS = " = " } ; {
        if ($1 == "host") {
                "'"./lookup.sh "'" $2 | getline fqdn
                $2 = "="; $3 = fqdn
        }
        print
}' $INFILE
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  • Hah, I was asking for it... Yeah perl will work, thank you. Personally I try to do everything in bash but you can't argue with results. Thanks again, just tested and it does what I need. Commented Mar 28, 2016 at 22:01
  • Now if someone can tell me how to do the above in bash :) Commented Mar 28, 2016 at 22:01
  • @JoeMama I just included a pure bash/awk solution in the answer. Commented Mar 28, 2016 at 23:01
  • Of course, that's a pure bash/awk solution in the same sense that the perl script is a pure bash/perl solution. awk is no more a part of "pure" sh or bash than perl is, it's just another external (to sh/bash) scripting language. Commented Mar 29, 2016 at 1:23

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