How to pass a list of variables into sed in a shell function

Question

I want to append multiple variables to the end of a line that contains a certain string. Here is my function:

function () { sudo sed -i '/^STRING/ s/$/ '$@'/' FILE; }

However I got sed: -e expression #1, char 24: unterminated `s' command

How can I pass all arguments of this function to sed?

Example:

The file is like:

sometext
sometext STRING sometext
sometext

After I execute the command function test1 test2, the file should be changed to

sometext
sometext STRING sometext test1 test2
sometext

Answer 1

You aren't appending “multiple variables”. You're appending a string. The most straightforward interface for your function would be to call it with a single string as its argument:

myfunction 'test1 test2'

and then (not using function as the function name because it's a keyword in some shells)

myfunction () {
  sudo sed -i "/^STRING/ s/\$/ $1/" FILE
}

Beware that this doesn't actually append the specified string, because the argument is interpolated into the sed script. Any / or \ in the argument is not interpreted literally. You can work around that by first preparing the argument:

myfunction () {
  extra=$(printf '%s\n' "$1" | sed 's![\\/]!\\&!g')
  sudo sed -i "/^STRING/ s/\$/ $extra/" FILE
}

Alternatively you can use another tool such as perl:

myfunction () {
  sudo env extra="$1" perl -i -pe '/^STRING/ s/$/\Q$ENV{extra}/' FILE
}

If you absolutely want your function to take a series of strings as arguments, and append them all in order with a space in between, then you can use "$*". This expands to a single word containing all the arguments of the function with a space in between.

myfunction () {
  extra=$(printf '%s\n' "$*" | sed 's![\\/]!\\&!g')
  sudo sed -i "/^STRING/ s/\$/ $extra/" FILE
}