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Table of Contents
fScan Reference Manual, Chapter 1 (Topics): status
Status queries -- Command operators to query data status
fScan command lines and interactive command strings can contain special query operators that test the status of data elements. The queries return either a 1 or 0 value, depending on whether the query result was yes or no.
The data definition query -- ?
usage: ?data
The '?' query operator can be used in place of the '$' data name identifier in any fScan command string. Whereas $dataname would be replaced in the command by the value of the variable DATANAME, ?dataname is replaced by either 1 or 0 depending on whether the variable DATANAME contains a valid data value or not. A query on an undefined data variable would always return status 0.
The file found query -- ?exists
usage: ?exists(filename)
or: $exists(filename)
The EXISTS query operator test whether its argument string is the name of an existing data file. It returns 1 if the file was found, 0 if the file was not found.
See Also:
IF
