classad_eval

Evaluate the given ClassAd expression(s) in the context of the given ClassAd attributes, and prints the result in ClassAd format.

Synopsis

classad_eval [-file <name>] <ad | assignment | expression>+

Description

classad_eval is designed to help you understand and debug ClassAd expressions. You can supply a ClassAd on the command-line, or via a file, as context for evaluating the expression. You may also construct a ClassAd one argument at a time, with assignments.

By default, clasad_eval will print the ClassAd context used to evaluate the expression before printing the result of the first expression, and for every expression with a new ClassAd thereafter. You may suppress this behavior with the -quiet flag, which replaces an ad, assignment, or expression, and quiets every expression after it on the command line.

Attributes specified on the command line, including those specified as part of a complete ad, replace attributes in the context ad, which starts empty. You can’t remove attributes from the context ad, but you can set them to undefined.

Examples

Almost every ad, assignment, or expression will require you to single quote them. There are some exceptions; for instance, the following two commands are equivalent:

$ classad_eval 'a = 2' 'a * 2'
$ classad_eval a=2 a*2

You can specify attributes for the context ad in three ways:

$ classad_eval '[ a = 2; b = 2 ]' 'a + b'
$ classad_eval 'a = 2; b = 2' 'a + b'
$ classad_eval 'a = 2' 'b = 2' 'a + b'

You need not supply an empty ad for expressions that don’t reference attributes:

$ classad_eval 'strcat("foo", "bar")'

If you want to evaluate an expression in the context of the job ad, first store the job ad in a file:

$ condor_q -l 1777.2 > 1227.2.ad
$ classad_eval -file 1277.2.ad 'JobUniverse'

You can extract a machine ad in a similar way:

$ condor_status -l exec-17 > exec-17.ad
$ classad_eval -file exec-17.ad 'Rank'

You can not supply more than one ad to classad_eval. Assignments (including whole ClassAds) are all merged into the context ad:

$ classad_eval 'x = y' 'x' 'y = 7' 'x' 'x=6' 'x'
[ x = y ]
undefined
[ y = 7; x = y ]
7
[ y = 7; x = 6 ]
6

You can suppress printing the context ad partway through:

$ classad_eval -file example 'x' -quiet 'y = 7' 'x' 'x=6' 'x'
[ x = y ]
undefined
7
6

Exit Status

Returns 0 on success.

Author

Center for High Throughput Computing, University of Wisconsin-Madison