Running docker exec command with a shell string and parameters in bash script

Question

I'm trying to run the following docker exec command in a bash script where I'm passing 2 parameters into the bash script. The command is supposed to delete directories that begin with a certain string. I don't seem to be passing in the parameters correctly:

• $container is set to $1

• $database is set to $2

• $currdate is set internally in the bash script

  docker exec $container sh -c 'rm -rf /path/to/directory/${database}-${currdate}-*/'

Answer 1

You have to use double quotes to interpolate variables. Single quotes won't interpolate anything, but double quotes will.

docker exec $container sh -c "rm -rf /path/to/directory/${database}-${currdate}-*/"

From Bash manual:

3.1.2.2 Single Quotes

Enclosing characters in single quotes (') preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.

3.1.2.3 Double Quotes

Enclosing characters in double quotes (") preserves the literal value of all characters within the quotes, with the exception of $, `, \, and, when history expansion is enabled, !. The characters $ and ` retain their special meaning within double quotes (see Shell Expansions). The backslash retains its special meaning only when followed by one of the following characters: $, `, ", \, or newline. Within double quotes, backslashes that are followed by one of these characters are removed. Backslashes preceding characters without a special meaning are left unmodified. A double quote may be quoted within double quotes by preceding it with a backslash. If enabled, history expansion will be performed unless an ! appearing in double quotes is escaped using a backslash. The backslash preceding the ! is not removed.

The special parameters * and @ have special meaning when in double quotes (see Shell Parameter Expansion).