=head1 NAME

recs-eval

=head1 recs-eval --help-all

 Help from: --help-basic:
 Usage: recs-eval <args> <expr> [<files>]
    <expr> is evaluated as perl on each record of input (or records from <files>)
    with $r set to a App::RecordStream::Record object and $line set to the
    current line number (starting at 1). The result of each evaluation is printed
    on a line by itself (this is not a recs stream). See
    App::RecordStream::Record for help on what the $r object can do. See --help-
    snippets for more information on code snippets
 
    --e                          a perl snippet to execute, optional
    --E                          the name of a file to read as a perl snippet
    --M module[=...]             execute "use module..." before executing
                                 snippet; same behaviour as perl -M
    --m module[=...]             same as -M, but by default import nothing
    --chomp                      Chomp eval results (to avoid duplicate newlines
                                 when already newline-terminated)
    --filename-key|fk <keyspec>  Add a key with the source filename (if no
                                 filename is applicable will put NONE)
 
   Help Options:
       --help-all       Output all help for this script
       --help           This help screen
       --help-keyspecs  Help on keyspecs, a way to index deeply and with regexes
       --help-snippet   Help on code snippets
 
 Examples:
    Print the host field from each record.
       recs-eval '$r->{host}'
    Prepare to gnuplot field y against field x.
       recs-eval '$r->{x} . " " . $r->{y}'
    Set up a script (this would be presumably piped to sh)
       recs-eval '"./myscript --value $r->{foo}"'
 
 Help from: --help-keyspecs:
   KEY SPECS
    A key spec is short way of specifying a field with prefixes or regular
    expressions, it may also be nested into hashes and arrays. Use a '/' to nest
    into a hash and a '#NUM' to index into an array (i.e. #2)
 
    An example is in order, take a record like this:
 
      {"biz":["a","b","c"],"foo":{"bar 1":1},"zap":"blah1"}
      {"biz":["a","b","c"],"foo":{"bar 1":2},"zap":"blah2"}
      {"biz":["a","b","c"],"foo":{"bar 1":3},"zap":"blah3"}
 
    In this case a key spec of 'foo/bar 1' would have the values 1,2, and 3 in
    the respective records.
 
    Similarly, 'biz/#0' would have the value of 'a' for all 3 records
 
    You can also prefix key specs with '@' to engage the fuzzy matching logic
 
    Fuzzy matching works like this in order, first key to match wins
      1. Exact match ( eq )
      2. Prefix match ( m/^/ )
      3. Match anywehre in the key (m//)
 
    So, in the above example '@b/#2', the 'b' portion would expand to 'biz' and 2
    would be the index into the array, so all records would have the value of 'c'
 
    Simiarly, @f/b would have values 1, 2, and 3
 
    You can escape / with a \. For example, if you have a record:
    {"foo/bar":2}
 
    You can address that key with foo\/bar
 
 Help from: --help-snippet:
    CODE SNIPPETS:
     Recs code snippets are perl code, with one exception. There a couple of
     variables predefined for you, and one piece of special syntax to assist in
     modifying hashes.
 
 Special Variables:
     $r - the current record object. This may be used exactly like a hash, or you
     can use some of the special record functions, see App::RecordStream::Record
     for more information
 
     $line - This is the number of records run through the code snippet, starting
     at 1. For most scripts this corresponds to the line number of the input to
     the script.
 
     $filename - The filename of the originating record. Note: This is only
     useful if you're passing filenames directly to the recs script, piping
     from other recs scripts or from cat, for instance, will not have a
     useful filename.
 
 Special Syntax
     Use {{search_string}} to look for a string in the keys of a record, use /
     to nest keys. You can nest into arrays by using an index. If you are
     vivifying arrays (if the array doesn't exist, prefix your key with # so
     that an array rather than a hash will be created to put a / in your key,
     escape it twice, i.e. \/
 
     This is exactly the same as a key spec that is always prefaced with a @, see
     'man recs' for more info on key specs
 
     For example: A record that looks like:
     { "foo" : { "bar 1" : 1 }, "zoo" : 2}
     Could be accessed like this:
 
     # value of zoo  # value of $r->{foo}->{bar 1}: (comma separate nested keys)
     {{zoo}}         {{foo/ar 1}}
 
     # Even assign to values (set the foo key to the value 1)
     {{foo}} = 1
 
     # And auto, vivify
     {{new_key/array_key/#0}} = 3 # creates an array within a hash within a hash
 
     # Index into an array
     {{array_key/#3}} # The value of index 3 of the array ref under the
     'array_key' hash key.
 
     This matching is a fuzzy keyspec matching, see --help-keyspecs for
     more details.
 

=head1 SEE ALSO

=over

=item * See L<App::RecordStream> for an overview of the scripts and the system

=item * Run C<recs examples> or see L<App::RecordStream::Manual::Examples> for a set of simple recs examples

=item * Run C<recs story> or see L<App::RecordStream::Manual::Story> for a humorous introduction to RecordStream

=item * Every command has a C<--help> mode available to print out usage and
examples for the particular command, just like the output above.

=back

