On the fly COLORING and UNDERLINING (a la FISH)

[gvsteen]

Dear Bash developers, 

We are long-time users of Bash. A few years ago we encountered an alternative 
Linux shell called Fish (www.fisshell.org). For us this shell has some 
compelling features that we would love to avail of in Bash: 

1."On the fly COLORING": If you type the name of a binary - or a command - you 
can immediately see if that binary - or command - exists, because if it exists 
it would be shown in green on the command-line. If the binary does not exist it 
will be shown in red, so that you know that the binary/command is not 
available. This may indicate to you that you made a typo. Fish also colors 
syntactic constructs on the fly. The same applies to mismatched parentheses and 
quotes. 

2."On the fly UNDERLINING": If you start typing the name of a file - or a 
command - you can immediately see if the pattern you typed so far coincides 
with an actual file - or command - on your system. If a file matching the 
pattern exists, it will be underlined. If a file matching the pattern does not 
exist, what you type will not be underlined. 

The main reason why we do not want to keep using Fish is that Fish provides its 
own scripting language, which is incompatible with Bash syntax. So we would be 
very happy if the requested features could be implemented in Bash. We also 
think that these two features may be useful to many other Bash users. 
Therefore, we would like to ask how difficult it is to implement them in Bash, 
and if the Bash developers would be interested in putting them on Bash's wish 
list. 

Best wishes, 

Guido van Steen, Isaac Dupree and Benny Cherniavsky 

P.S. Installing Fish under Debian/Ubuntu just takes "sudo apt-get install 
fish". It is also available for Fedora through "yum install fish". For those 
interested in a VMware image with Fish installed, we can upload an Debian image 
to you of about 100MB with Fish installed as the main shell.