LIGOtools Package: metaio

• A library (libmetaio.a) which allows a C program to parse a file containing a metadata table in LIGO_LW XML format. Note that, prior to version 6.0, these functions were contained in the library libdataflow.a in the 'dataflow' package.

• Utilities to manipulate metadata tables in LIGO_LW files:
  • lwtscan to print the table's columns and the number of rows
  • lwtcut to select certain rows from a table based on a numeric comparison and/or row number, report the number of matching rows, and optionally write the matching rows to a new LIGO_LW file
  • lwtprint to print selected columns/rows as plain text
  • lwtdiff to compare the data in two files (allowing for formatting variations which do not affect the content)
  • lwtselect to extract a single Table object from a LIGO_LW file containing multiple Table objects
  • concatMeta to concatenate LIGO_LW files containing database table data

• The Matlab MEX-file readMeta, which reads the contents of a LIGO_LW metadata file into Matlab arrays.

Authors:

• Philip Charlton (for the "metaio" library code)
• Peter Shawhan (for the utilities)
• Duncan Brown (packaging)

Version 7.2

Frequently Asked Questions related to this package

• How can I read a LIGO_LW file of table entries into Matlab?
• How can I read a LIGO_LW file of table entries into a C program?
• How can I select certain entries from a LIGO_LW table file?
• What else can I do with a LIGO_LW file of table entries?

Notes

• This package is distributed via 'ligotools_update' as a SOURCE distribution and also in a version precompiled for Solaris. The C code components are compiled with gcc and made into a library automatically when the package is installed. If for some reason you aren't able to compile them, you can get the precompiled binary distribution files below.

• A few utilities in this package use the tclshexe program from the LIGOtools package 'tclexe', so that package must be installed and active.

• The master copy of the metaio library code and utilities is the lscsoft CVS repository. This LIGOtools package is derived directly from the code that is in the CVS repository, here.

Documentation

• Typing lwtscan, lwtcut, lwtprint, lwtdiff, lwtselect, or concatMeta without any arguments will print out usage information - in most cases, rather detailed.

• By default, lwtprint uses a comma to separate the values it prints out. To use a space as a separator, use the -d option, e.g.:
   lwtprint myfile.xml -d " "

• Example C program to perform a simple coincidence test on two input LIGO_LW files with events, e.g. from the gds_trigger table: find_coinc.c.
  To compile this, do:
   gcc find_coinc.c $LIGOTOOLS/lib/libmetaio.a -I$LIGOTOOLS/include -o find_coinc

• There is no formal documentation about how to use the "Metaio" C library. However, you can see the comments in the source code for the library in $LIGOTOOLS/packages/metaio/7.2/src/metaio.c, and look at the utility programs $LIGOTOOLS/packages/metaio/7.2/src/lwt*.c as examples. Also see this code for an example of how to write out selected rows of an input LIGO_LW file: ivana_16jul02.c (search for "outEnv").

Distribution files

• Source distribution: metaio_7.2_SOURCE.tar.gz (684 kb)
  This is known to build properly on Solaris and Linux using gcc; other operating systems or compilers may require some modifications. If you figure out how to do this, please let me know.
• Generic Solaris distribution (built on canopus.ligo.caltech.edu): metaio_7.2_SunOS.tar.gz (97 kb)
• Precompiled binary versions for various platforms and versions of Matlab can be downloaded from the DASWG metaio project page and installed using ligotools_install.