dbrowcount man page

dbrowcount — count the number of rows in an Fsdb stream

Synopsis

dbrowcount

Description

Count the number of rows and write out a new fsdb file with one column (n) and one value: the number of rows. This program is a strict subset of dbcolstats.

Although there are other ways to get a count of rows ("dbcolstats", or "dbrowaccumulate -C 1" and some processing), counting is so common it warrants its own command. (For example, consider how often "wc -l" is used in regular shell scripting.) There are some gross and subtle differences, though, in that "dbrowcount" doesn't require one to specify a column to search, and it also doesn't look for and skip null data items.

Options

No program-specific options.

This module also supports the standard fsdb options:

-d

Enable debugging output.

-i or --input InputSource

Read from InputSource, typically a file name, or "-" for standard input, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.

-o or --output OutputDestination

Write to OutputDestination, typically a file name, or "-" for standard output, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.

--autorun or --noautorun

By default, programs process automatically, but Fsdb::Filter objects in Perl do not run until you invoke the run() method. The "--(no)autorun" option controls that behavior within Perl.

--help

Show help.

--man

Show full manual.

Sample Usage

Input

    #fsdb      absdiff
    0
    0.046953
    0.072074
    0.075413
    0.094088
    0.096602
    #  | /home/johnh/BIN/DB/dbrow 
    #  | /home/johnh/BIN/DB/dbcol event clock
    #  | dbrowdiff clock
    #  | /home/johnh/BIN/DB/dbcol absdiff

Command

    cat data.fsdb | dbrowcount

Output

    #fsdb n
    6
    #  | /home/johnh/BIN/DB/dbrow 
    #  | /home/johnh/BIN/DB/dbcol event clock
    #  | dbrowdiff clock
    #  | /home/johnh/BIN/DB/dbcol absdiff

Input 2

As another example, this input produces the same output as above in "dbrowcount", but different output in "dbstats":

    #fsdb      absdiff
    -
    -
    -
    -
    -
    -
    #  | /home/johnh/BIN/DB/dbrow 
    #  | /home/johnh/BIN/DB/dbcol event clock
    #  | dbrowdiff clock
    #  | /home/johnh/BIN/DB/dbcol absdiff

See Also

dbcolaccumulate(1), dbcolstats(1), Fsdb(3)

Info

2017-07-28 perl v5.26.0 User Contributed Perl Documentation