diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 30 |
1 files changed, 29 insertions, 1 deletions
@@ -38771,7 +38771,25 @@ The expressions .meta from-condition and .meta to-condition -are ordinary expressions which are evaluated; however, the are evaluated +are ordinary expressions which are evaluated. However, their +evaluation is unusual in two ways. + +Firstly, if either expression +produces, as its result, a function or regular expression object, +then that function or regular expression object is applied to +the current record (value of the +.code rec +variable), and the result of that application is then taken +as the result of the condition. This allows for expressions like +.code "(rng (f^ #/start/) #/end/)" +which denotes a range which begins with a record which +begins with the prefix +.str start +and ends with a record which contains +.str end +as a substring. + +Secondly, the conditions are evaluated out of order with respect to the surrounding expression in which they occur. Ranges and their constituent .meta from-condition @@ -38813,6 +38831,16 @@ itself is evaluated, the expression merely fetches a previously computed Boolean value which indicates whether the range is active for this record. +Also, the behavior is unspecified if range expressions attempt to modify +the awk-special variables. +.codn rec , +.codn f , +.codn fs , +.code ft +or +.codn kfs . +It is not recommended to place any side effects into range expressions. + Evaluation of ranges obeys the following logic, which is applied to each range, prior to the processing of condition-action clauses. If a range is not currently active, its |