FILE.EXISTS (U-SQL)

아티클
03/10/2017

Summary

Checks if a file in the specified location exists at compile time.

Syntax

bool EXISTS(
    string path
).

Parameters

path
A constant-foldable string expression. path can be any supported file path Universal Resource Identifier (URI). If path is not constant-foldable, the error E_CSC_USER_EXPRESSIONNOTCONSTANTFOLDABLE is raised. If path is empty (null or the zero-length string), the error E_CSC_USER_EMPTYFILEPATH is raised. If path contains invalid characters, the error E_CSC_USER_INVALIDFILENAME is raised.

Return Value

bool
True if path exists and the user has access to it. False if path does not exists, refers to a folder or the user has no access to it.

Examples

The example can be executed in Visual Studio with the Azure Data Lake Tools plug-in.
The example below uses the sample data provided with your Data Lake Analytics account. See Prepare source data for additional information.

DECLARE @filepath_good = "/Samples/Data/SearchLog.tsv";
DECLARE @filepath_bad = "/Samples/Data/zzz.tsv";
 
@result =
    SELECT  FILE.EXISTS(@filepath_good) AS exists_good,
            FILE.EXISTS(@filepath_bad) AS exists_bad
    FROM (VALUES (1)) AS T(dummy);
 
OUTPUT @result
TO "/Output/ReferenceGuide/BuiltInFunctions/SystemFunctions/FileExists.txt"
USING Outputters.Csv();

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