1Fsdb::IO::Reader(3) User Contributed Perl Documentation Fsdb::IO::Reader(3)
2
6 Fsdb::IO::Reader - handle formatting reading from a fsdb file (handle)
7 or queue
8
10 Sample code reading an input stream:
11 $in = new Fsdb::IO::Reader(-file => '-');
13 $in->error and die "cannot open stdin as fsdb: " . $in->error . "\n";
14 my @arow;
15 while ($in->read_row_to_aref(\@arow) {
16 # do something
17 };
18 $in->close;
19
21 new
22 $fsdb = new Fsdb::IO::Reader(-file => $filename);
23 $fsdb = new Fsdb::IO::Reader(-header => "#fsdb -F t foo bar", -fh => $file_handle);
24 Creates a new reader object from FILENAME. (FILENAME can also be a
26 IO::Handle object.) Always succeeds, but check the "error" method to
27 test for failure.
28 Options:
30 other options See also the options in Fsdb::IO, including "-file",
32 "-header".
33 -file FILENAME Open and read the given filename.
34 -comment_handler $ref
35 Define how comments are handled. If $REF is a Fsdb::IO::Writer
36 object, comments are written to that stream as they are
37 encountered. if $REF is a ref to a scalar, then we assume that
38 scalar will be filled in with a Fsdb::IO::Writer object later and
39 treat it the same. If it is of type code, then it is assumed to be
40 a callback function of the form:
41 sub comment_handler ($) { my $comment = @_; }
43 where the one argument will be a string with the unparsed comment
45 (with leading # and trailing newline).
46 By default, or if $ref is undef, comments are consumed.
48 A typical handler if you have an output Fsdb stream is:
50 sub { $out->write_raw(@_); };
52 (That is the code created by
54 Fsdb::Filter::create_pass_comments_sub.)
55 There are several support routines to handle comments in a
57 pipeline; see Fsdb::Filter::create_pass_comments_sub,
58 Fsdb::Filter::create_tolerant_pass_comments_sub,
59 Fsdb::Filter::create_delay_comments_sub.
60 User-specified -header arguments override a header provided in the
62 input source.
63 config_one
65 documented in new
66 comment_handler_to_sub;
68 internal use only: parses and sets up the comment handle callback. (At
69 input, _comment_sub is as given by -comment_handler, but at exit it is
70 always an anon function.
71 _enable_compression
73 $self->_enable_compression
74 internal use only: switch from uncompressed to compressed.
76 create_io_subs
78 $self->create_io_subs()
79 internal use only: create a thunk that returns rowobjs.
81 read_headerrow
83 internal use only; reads the header
84 read_rowobj
86 $rowobj = $fsdb->read_rowobj;
87 Reads a line of input and returns a "row object", either a scalar
89 string for a comment or header, or an array reference for a row, or
90 undef on end-of-stream. This routine is the fastest way to do full-
91 featured fsdb-formatted IO. (Although see also
92 Fsdb::Reader::fastpath_sub.)
93 Unlike all the other routines (including fastpath_sub), read_rowobj
95 does not do comment processing (calling comment_sub).
96 read_row_to_aref
98 $fsdb->read_row_to_aref(\@a);
99 Then $a[0] is the 0th column, etc. Returns undef if the read fails,
101 typically due to EOF.
102 unread_rowobj
104 $fsdb->unread_rowobj($fref)
105 Put an fref back into the stream.
107 unread_row_from_aref
109 $fsdb->unread_row_from_aref(\@a);
110 Put array @a back into the file.
112 read_row_to_href
114 $fsdb->read_row_to_href(\%h);
115 Read the next row into hash %h. Then $h{'colname'} is the value of
117 that column. Returns undef if the read fails, typically due to EOF.
118 unread_row_from_href
120 $fsdb->unread_row_from_href(\%h);
121 Put hash %h back into the file.
123 fastpath_ok
125 $fsdb->fastpath_ok();
126 Check if we can do fast-path IO (post-header, no pending unread rows,
128 no errors).
129 fastpath_sub
131 $sub = $fsdb->fastpath_sub()
132 $row_aref = &$sub();
133 Return an anonymous sub that does read fast-path when called. This
135 code stub returns a new $aref corresponding with a data line, and
136 handles comments as specified by -comment_handler
137perl v5.28.1 2018-12-19 Fsdb::IO::Reader(3)