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### 4.2 Input Locations

In many cases loading tables will be done using GUI dialogues such as the Filestore Load Window, where you just need to click on a filename or directory to indicate the load location. However in some cases, for instance specifying tables on the command line (Section 10.1) or typing pathnames directly into the Load Window Location field, you may want give the location of an input table using only a single string.

Most of the time you will just want to type in a filename; either an absolute pathname or one relative to TOPCAT's starting directory 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 an HTTP resource.
`https:`
  Read from an HTTPS resource.
`ftp:`
  Read from an anonymous FTP resource.
`file:`
  Read from a local file, using the syntax `file:///path/to/file`. This is similar to specifying the filename directly, but there is a difference: using this form forces reads to be sequential rather than random access, which may allow you to experience a different set of performance characteristics and bugs.
`jar:`
  Specialised protocol for looking inside Java Archive files - see JarURLConnection documentation.
`myspace:`
  (Obsolete?) 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. Not available in the Debian version of TOPCAT.
`ivo:`
  (Obsolete?) 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. Not available in the Debian version of TOPCAT.
`jdbc:`
  JDBC URLs may be used, but they don't work in the same way as the others listed here, since they do not reference an input byte stream. See instead Section 4.3.3.

From the command line 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.

Note that tables can also be supplied by name from non-serialized sources, as described in Input Schemes.

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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@jiscmail.ac.uk