Using sed to substitute string in in double quote with a bash variable

Question

I have a yaml file that I am trying to create a number within a loop and replace it with the newly computed variable.

The line i wish to replace looks like this:

 # genesis_gas_limit:            "16000000" ## Used to set genesis gas limit

I plan on putting this in a loop and thus I would love it if the sed could take a wild card i.e.

 # genesis_gas_limit:            "*" ## Used to set genesis gas limit

I have have tried this

sed -i 's/ genesis_gas_limit:/c\ genesis_gas_limit: $GASLIMIT' examples/values-local.yaml

but i get the following error:

sed: 1: "examples/values-local.yaml": invalid command code e

I would appreciate any pointers on this

This might help: Difference between single and double quotes in bash — Cyrus
– Cyrus, Commented Oct 14, 2019 at 17:21

janos · Accepted Answer · 2019-10-14 17:38:00Z

1

You could replace genesis_gas_limit: and whatever content follows it, with genesis_gas_limit: and the new value. Using GNU sed:

sed -i "s/ genesis_gas_limit:.*/ genesis_gas_limit: \"$GASLIMIT\"/" examples/values-local.yaml

Using BSD sed (in OSX):

sed -i.bak -e "s/ genesis_gas_limit:.*/ genesis_gas_limit: \"$GASLIMIT\"/" examples/values-local.yaml

edited Oct 14, 2019 at 17:38

answered Oct 14, 2019 at 17:28

janos

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5 Comments

0xsegfault Over a year ago

Thanks fro your help. From this site i gathered i need to include "" to the sed command ed.gs/2016/01/26/os-x-sed-invalid-command-code. When i use it with your answer , it doesnt error. however, it doesnt substitute the string in the file. do you . know what might be wrong?

0xsegfault Over a year ago

when i used sed -e it does replace the line, but doesnt substitute the variable

janos Over a year ago

@SamuelDare are you using GNU or BSD version of sed? (Look at your man sed)

0xsegfault Over a year ago

using an OSX so BSD

Gordon Davisson Over a year ago

@SamuelDare BSD sed has a slightly different syntax for editing files in place. Its -i option requires a backup extension parameter; if you don't want to make a backup, you must explicitly supply an empty parameter after -i (that is, sed -i "" instead of just sed -i). In your original command, BSD sed will interpret the entire 's/ ... will be taken as the backup extension, and it'll try to interpret examples/values-local.yaml as the sed command to execute.

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