4.5.1 Utilizing log-file comments

<output_stmt>s and <log_stmt>s have limited access to the <key:value> pairs that are written as comments at the top of every log file as shown in Log-file format. Given a key, key, the string expression ‘THE VALUE OF key’ represents the value associated with that key or the empty string if key does not appear in the log-file comments:

That is, ‘"CPU frequency"’ means the literal string “CPU frequency” while ‘THE VALUE OF "CPU frequency"’ translates to a string like “1300000000 Hz (1.3 GHz)”. Environment variables are also considered keys and are therefore acceptable input to a THE VALUE OF construct.