IDL Reference Guide: Procedures and Functions

QUERY_ASCII

The QUERY_ASCII function tests a file for compatibility with READ_ASCII and returns an optional structure containing information about the file.

This routine is written in the IDL language. Its source code can be found in the file query_ascii.pro in the lib subdirectory of the IDL distribution.

Syntax

Result = QUERY_ASCII( Filename [, Info] )

Return Value

This routine returns a long integer with the value of 1 (one) if the query was successful (and the file type was correct) or 0 (zero) on failure. The following criteria are used to decide whether a file is a valid ASCII file:

These criteria provide an efficient and robust method to filter ASCII files from non-ASCII files. The 80% figure lets an ASCII file have a certain number of non-ASCII characters, perhaps in a header portion or for special characters such as fractions or symbols.

Arguments

Filename

A scalar string containing the full pathname of the file to query.

Info

Set this optional argument to a named variable in which to return an anonymous structure containing information about the file. This structure is valid only when the return value of the function is 1. The structure has the following fields:

For the WORDS field, words are assumed to be separated by whitespace, including carriage returns, line feeds, tabs, and spaces.

Keywords

None

Example

Use the following code to retrieve information from a text file:

file = FILEPATH( "irreg_grid1.txt", $  
   SUBDIRECTORY=['examples','data'] )  
result = QUERY_ASCII( file, info )  
if (result) then HELP, info, /STRUCTURES $  
   else PRINT, 'File not found or is not a valid ASCII file.'