q:tldr:6ea84

The given command is written in a query language, which is likely SQL. Let's break it down step by step:

1. The command starts with "q" which is presumably a shorthand or an alias for executing a SQL query.
2. The query itself is enclosed in double quotation marks.
3. The query begins with "SELECT FROM" which indicates that we want to select all columns ("") from a table or tables.
4. The table name is specified as "${filename}", where "${filename}" is a placeholder for the actual name of the table. This means that the name of the table is stored in a variable or parameter. The value of "${filename}" needs to be substituted with the table name before executing the query.
5. The query uses the "JOIN" keyword to combine multiple tables. The first table is referenced as "f1" (an alias) and the second table is referenced as "${path-to-other_file}", where "${path-to-other_file}" is a placeholder for the location or name of the second table. Similar to "${filename}", the value of "${path-to-other_file}" needs to be substituted with the actual path or name of the second table.
6. The condition for the join is specified with "ON (f1.c1 = f2.c1)", where "f1.c1" represents a column in the first table "f1" and "f2.c1" represents a column in the second table "f2". This condition states that the join should be performed where the values in "f1.c1" are equal to the values in "f2.c1".

In summary, this command executes a SQL query that selects all columns from a table named "${filename}" and joins it with another table specified by "${path-to-other_file}" based on a common column called "c1" in both tables.