Question

I’m trying to replace a number that is in a couple different strings in a text file. Basically it would take the form of

tableNameNUMBER
carNUMBER

I’m pretty new to bash and scripting and I wasn’t sure how to replace NUMBER with what I pass in. So I’ve tried this:

#! /usr/bin/env bash
sed "s/NUMBER/$1/" myScript.txt > test.txt

then at the command line:

sh test.sh 123456

This only works if NUMBER is on its own, without tableName or car preceding it. How can I replace NUMBER in those cases. Is it better to have ${NUMBER}? Sorry if these are totally noob questions.

Answer 1

This should work just fine:

sed "s/NUMBER/$1/g" myScript.txt > test.txt

The g on the end allows set to replace NUMBER if it appears multiple times on one line.

In fact, a quick test:

foo.txt

carNUMBER
tableNameNUMBER
NUMBER
NUMBERfoo

$ NUMBER=3.14
$ sed "s/NUMBER/$NUMBER/g" foo.txt
car3.14
tableNumber3.14
3.14
3.14foo

Isn’t that what your sed command is doing?

If you want to make sure you don’t change NUMBER unless it’s by itself, use \b around NUMBER:

$ sed "s/\bNUMBER\b/$NUMBER/g" foo.txt
carNumber
tabelNumberNUMBER
3.14
NUMBERfoo

If you don’t care about the case of the string NUMBER, put an i on the end of the sed command:

$ sed "s/NUMBER/$NUMBER/gi" foo.txt