diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 57 |
1 files changed, 56 insertions, 1 deletions
@@ -739,6 +739,11 @@ A skip is also an anonymous block. Treat the remaining query or subquery as a match for a trailing context. That is to say, if the remainder matches, the data position is not advanced. +.IP @(freeform) +Treat the remainder of the input as one big string, and apply the following +query line to that string. The newline characters (or custom separators) appear +explicitly in that string. + .IP @(some) Match some clauses in parallel. At least one has to match. @@ -965,7 +970,7 @@ be written instead: end @BEG_SYMBOL @(end) -.SS The Trailer directive +.SS The Trailer Directive The trailer directive introduces a trailing portion of a query or subquery which matches input material normally, but in the event of a successful match, @@ -997,6 +1002,56 @@ after the second 111. With the @(trailer) directive in place, the collect body, on each iteration, only consumes the lines matched prior to @(trailer). +.SS The Freeform Directive + +The freeform directive provides a useful alternative to +.B txr's +line-oriented matching discipline. The freeform directive treats all remaining +input from the current input source as one big line. The directive which +immediately follows freeform is applied to that line. + +The syntax variations are: + + @(freeform) + ... query line .. + + @(freeform NUMBER) + ... query line .. + + @(freeform STRING) + ... query line .. + + @(freeform NUMBER STRING) + ... query line .. + +The string and numeric arguments, if both are present, may be given in either +order. + +If a numeric argument is given, it limits the range of lines which are combined +together. For instance @(freeform 5) means to only consider the next five lines +to to be one big line. Without a numeric argument, freeform is "bottomless". It +can match the entire file, which creates the risk of allocating a large amount +of memory. + +If a string argument is given, it specifies a custom line terminator. The +default terminator is "\en". The terminator does not have to be one character +long. + +In the following example, freeform is used to solve a tokenizing problem. The +Unix password file has fields separated by colons. Some fields may be empty. +Using freeform, we can join the password file using ":" as a separator. +By restricting freeform to one line, we can obtain each line of the password +file with a terminating ":", allowing for a simple tokenization, because +now the fields are colon-terminated rather than colon-separated. + +Example: + + @(next "/etc/passwd") + @(collect) + @(freeform 1 ":") + @(coll)@{token /[^:]*/}:@(end) + @(end) + .SS The Some, All, None and Maybe directives These directives combine multiple subqueries, which are applied at the same position in parallel. The syntax of all three follows this example: |