Find a string and replace the entire line for that string

Question

I need to update the value of a specifc key (say, key2) in the yaml file using shell command. I am trying to use sed but it is working only if I have a specific value, for example, TBD in this case. But I want to update the value everytime irrespective of any value. Also my replacement string is stored in a variable. Can anybody suggest me what command shall I use?

hash.yaml file

---
key1: val1
key2: <TBD>
key3:
 - val3_1
 - val3_2

This is what I tried and works for me. But only if I have "TBD" as my search key.

sed -i "s;<TBD>;$var;g" hash.yaml

Sed is not the right tool to parse YAML

Gilles Quénot
– Gilles Quénot

2016-10-13 22:13:34 +00:00
Commented Oct 13, 2016 at 22:13 — Gilles Quénot
– Gilles Quénot, Commented Oct 13, 2016 at 22:13

anubhava · Accepted Answer · 2016-10-13 22:08:13Z

1

You can use this sed to replace any value of the key key2 with the new value stored in a variable called $var:

var='foobar'

sed -E "s~^([ \t]*key2:[ \t]*).*~\1$var~" hash.yml

key1: val1
key2: foobar
key3:
 - val3_1
 - val3_2

In the expression ^([ \t]*key2:[ \t]*).* we match key2: at line start with optional whitespace before and after it. .* in the end will match anything for key2.

If you want to edit file in-place then use -i flag for sed:

sed -i '' -E "s~^([ \t]*key2:[ \t]*).*~\1$val~" hash.yml

answered Oct 13, 2016 at 22:08

anubhava

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Gilles Quénot · Accepted Answer · 2016-10-13 22:17:04Z

0

Using a proper YAML parser in perl (the right tool for the right job...) :

#!/usr/bin/perl

use Config::YAML;
use YAML::XS qw/DumpFile/;

my $ds = Config::YAML->new(
    config => "hash.yaml"
);

$ds->{key2} = 'FOOBAR';

DumpFile("./new.yaml", $ds);

then,

cat new.yaml

answered Oct 13, 2016 at 22:17

Gilles Quénot

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