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The BROWSER project

What comes next after the classic Unix environment variables PAGER, MAILER, and EDITOR?

This is the BROWSER project page -- an effort to promulgate a convention for expressing your browser preference to programs which must call browsers to view URLs. Nowadays many programs must do this; mailer user agents and on-line help systems are just two of the most obvious application classes.

How BROWSER works:

The value of BROWSER may consist of a colon-separated series of browser command parts. These should be tried in order until one succeeds. Each command part may optionally contain the string "%s"; if it does, the URL to be viewed is substituted there. If a command part does not contain %s, the browser is to be launched as if the URL had been supplied as its first argument. The string %% must be substituted as a single %.

Rationale: We need to be able to specify multiple browser commands so programs obeying this convention can do the right thing in either X or console environments, trying X first. Specifying multiple commands may also be useful for people who share files like .profile across multiple systems. We need %s because some popular browsers have remote-invocation syntax that requires it. Unless %% reduces to %, it won't be possible to have a literal %s in the string.

For example, on most Linux systems a good thing to do would be:

BROWSER="netscape -raise -remote \"openURL(%s,new-window)\":lynx"

Who observes this convention?

In the near future, any Python program that uses the standard-library module. This module, which debuted in Python 2.0, was taught how to interpret BROWSER in CVS on 23 Jan 2001, and will be released in Python 2.1a2.

On 24 Jan 2001, a BROWSER patch against the 0.9 version was sent to the maintainers of urlview.

On 24 Jan 2001, a BROWSER patch was sent to the maintainer of the browser-launch code in GNU Emacs.

On 24 Jan 2001, a patch against the environ(5) man page was sent to Andries Brouwer, the Linux man page maintainer, adding BROWSER to the set of documented environment variables. Andries merged in an edited version within hours.

On 25 Jan 2001, Pavel Roskin told me "I hope to be able to implement $BROWSER support in xpdf but I cannot promise it."

What still needs to be done?

Key people in the Perl and Tcl communities (including Larry Wall) have agreed that it would be a good thing for the URL-viewing facilities in their language libraries to interpret BROWSER, but this has not been done yet.

If you implement BROWSER support somewhere, please let me know for this page.

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Eric S. Raymond <>