Updating a yaml with a string containing special characters using sed

Question

I have a yaml file that needs to be updated with string containing special characters. Here is the command I used but I get sed expression error

Yaml file (file):

Key1: 
Key2:

Command that works without special characters for $var (env variable):

sed  -i '0,/^\([[:space:]]*Key1: *\).*/s//\1'$var'/;' file

Value for $var:

fkugoiuhoiuyflkbbui/qy++bfv7J3c

Error I get is:

sed: -e expression #1, char 154: unknown option to `s'

I am trying to figure out how I can get this working. Any help is greatly appreciated. Thanks!

Yeah I cannot change the variable since its a fixed value and can contain any special character. — wasay, May 11 '22 at 20:29
Then in the `s` command replace the three `/` with one space each. See: [Escaping forward slashes in sed command](https://stackoverflow.com/q/40714970/3776858) — Cyrus, May 11 '22 at 20:54
I get an error `sed: -e expression #1, char 40: unknown command: `;'` Command: sed -i '0,/^$[[:space:]]*Key1: *$.* s \1'$var'/;' file — wasay, May 11 '22 at 21:20

score 0 · Accepted Answer · answered May 11 '22 at 20:34

0

The default delimiter of sed is conflicting with the / in your variable. You will need to set a different delimiter, further, the single quotes will not allow the variable to expand.

You can try this sed

$ sed "\|Key1|s|$|'$var'|" input_file
Key1: 'fkugoiuhoiuyflkbbui/qy++bfv7J3c'
Key2:

answered May 11 '22 at 20:34

HatLess

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Cool, this works. How do I make sure the variable value doesn't get appended on every run of the command and value is updated only for first occurence of "key1"? – wasay May 11 '22 at 20:57
@wasay `sed "0,\|Key1|{/Key1/s|$|'$var'|}" file` – HatLess May 11 '22 at 21:07
For some reason this is not working for me. The value doesn't get updated at all – wasay May 11 '22 at 21:19
`sed "0,\|Key1|{/$.*Key1:$.*/s||\1'$var'|}" file` @wasay – HatLess May 11 '22 at 21:31

glenn jackman · Answer 2 · 2022-05-12T03:13:44.103

This is an issue that can happen no matter what delimiter of s/// you pick. The proper solution is to handle whatever delimiter characters appear in the data

escaped=${var//\//\\\/}    # escape all slashes
sed  -i '0,/^\([[:space:]]*Key1: *\).*/s//\1'"${escaped}"'/;' file

Breaking that down:

this uses the ${parameter/pattern/string} "search and replace" form of Shell Parameter Expansion
if the pattern starts with a /, then it's a global search and replace
the pattern is \/ which is a single forward slash: it needs to be escaped so that it is not interpreted as the separator between the pattern and the string.
then comes the / actually separating the pattern and the replacement string
the replacement string is \\\/: \\ is a literal backslash (that needs to go into the sed command) and lastly \/ is a literal slash.

With yq, a YAML processing tool, we can write

yq -i eval '.Key1 = "'"$var"'"' file

This is using the "go" implementaton of yq

$ yq --version
yq (https://github.com/mikefarah/yq/) version 4.25.1

This works too. Can you explain why so many slashes in escaped variable please? Thanks Glenn! — wasay, May 11 '22 at 22:08

Updating a yaml with a string containing special characters using sed

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