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### 4.2 Table Locations

In many cases loading and saving tables will be done using GUI dialogues such as the filestore load and save windows, where you just need to click on a filename or directory to indicate the load/save location. However in some cases, for instance specifying tables on the command line (Section 10.1) or typing pathnames directly into the load/save dialogue windows, you may want give the location of a table for input or output using only a single string.

Most of the time you will just want to type in a filename; either an absolute or relative pathname can be used. However, TOPCAT also supports direct use of URLs, including ones using some specialised protocols. Here is the list of URL types allowed:

`http:`
  Read from HTTP resources.
`ftp:`
  Read from anonymous FTP resources.
`file:`
  Read from local files; not particularly useful since you can do much the same using just the filename.
`jar:`
  Specialised protocol for looking inside Java Archive files - see JarURLConnection documentation.
`myspace:`
  Accesses files in the AstroGrid "MySpace" virtual file store. These URLs look something like "`myspace:/survey/iras_psc.xml`", and can access files in the myspace are that the user is currently logged into. These URLs can be used for both input and output of tables. To use them you must have an AstroGrid account and the AstroGrid WorkBench or similar must be running; if you're not currently logged in a dialogue will pop up to ask you for name and password.
`ivo:`
  Understands ivo-type URLs which signify files in the AstroGrid "MySpace" virtual file store. These URLs look something like "`ivo://uk.ac.le.star/filemanager#node-2583`". These URLs can be used for both input and output of tables. To use them you must have an AstroGrid account and the AstroGrid WorkBench or similar must be running; if you're not currently logged in a dialogue will pop up to ask you for name and password.
`jdbc:`
  Used for communicating with SQL-compliant relational databases. These are a bit different to normal URLs - see Section 4.1.1.10 and Section 4.1.2.9.

It is also possible to use the special value "`-`" to mean standard input; in this case the file format must be specified explicitly using the `-f` flag, and not all formats can be streamed from stdin. Finally, the form "`<syscmd`" or equivalently "`syscmd|`" may be used to read from the standard output of a shell pipeline (probably only works on Unix-like systems).

As with the GUI-based load dialogues, data compression in any of the supported formats (gzip, bzip2, Unix compress) is detected and dealt with automatically for input locations.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk