The READS procedure performs formatted input from a string variable and writes the results into one or more output variables. This procedure differs from the READ procedure only in that the input comes from memory instead of a file.
This routine is useful when you need to examine the format of a data file before reading the information it contains. Each line of the file can be read into a string using READF. Then the components of that line can be read into variables using READS.
If FORMAT is not specified, IDL uses its default rules for formatting the input. FORMAT allows the format of the input to be specified in precise detail, using a FORTRAN-style specification. See Using Explicitly Formatted Input/Output .