Euse is a command line USE flag editor for Gentoo Linux.

What does it do? 
================
USE flags are central to Gentoo Linux. When you want to compile (in Gentoo
terminology emerge) a new package you can set a few USE flags to customize the
behavior of the build. At present you do this by editing the /etc/make.conf and
change the USE variable there. 

(Sounds like marketing material, don't bother to read this section :-;)
With euse you don't have to open the file to edit anymore. You can directly
add/delete/view USE flags from make.conf. When you want to enable a particular
USE flag you might want to find out what this flag does. At present, you can
grep on use.desc and use.local.desc to find the details of an USE flag. With
euse -i flag you can directly find out the details about an USE flag without
grepping many files. Read ahead to view the usage.

Usage
=====
# euse -c -d -e
Prints out the current setting of USE variable in make.conf, make.defaults, environment variable USE respectively. You can use them individually. E.g.
# euse -c

# euse -i
Prints all the use flags with descriptions and their current status.
1st Column - Use flag
2nd Column - Shows if the USE flag is enabled or disabled.
3rd Column - If USE flag is enabled this columns show where it has been
             enabled. C means make.conf, D means make.defaults, E means
             enviroment variable USE.
4th Column - Shows if the use flag is a global or local use flags.
             For local use flags the desc field(next column) begins with
             showing which package it belongs to in square brackets.
5th Column - Use flag description.
Use Flag | Enabled/Disabled | Conf/Env/Defaults | Global/Local | Desc
alpha            [-] [ ] [G] indicates that architecture is 64-bit Alpha
alsa             [+] [C] [G] Adds support for media-libs/alsa-lib (Advanced
                             Linux Sound Architecture)
moznocompose     [+] [C] [L] [net-www/mozilla] : If you do NOT want the web page
                             composer built with mozilla

# euse -i mozilla
Prints details of just mozilla.
mozilla          [-] [ ] [G] Adds mozilla support

# euse -E mozilla alsa
Enables mozilla alsa in make.conf. Accepts one or more arguments to enable.

Case 1:
If before executing this command the USE in make.conf looks like this:
USE="tiff doc"
After executing it becomes:
USE="tiff doc mozilla alsa"

Case 2:
If before executing this command the USE in make.conf looks like this:
USE="tiff doc -mozilla -alsa"
After executing it becomes:
USE="tiff doc mozilla alsa"

There are lot of other cases, but you get the idea.

# euse -D mozilla alsa
Disables mozilla alsa in make.conf. Accepts one or more arguments to enable.

Case 1:
If before executing this command the USE in make.conf looks like this:
USE="tiff doc"
After executing it becomes:
USE="tiff doc -mozilla -alsa"

Case 2:
If before executing this command the USE in make.conf looks like this:
USE="tiff mozilla doc  alsa"
After executing it becomes:
USE="tiff -mozilla doc -alsa"

There are lot of other cases, but you get the idea.

Special Case:
all is special flag. It is equivalent to * in USE setting. You can use "*"
instead. But is NOT recommended. There are high chances you'll just type *
instead of "*" and Euse will spit out some warnings. Note that * has be quoted
to prevent bash expanding the wildchar. You can use all with -E and -D. With -E
it'll remove the last occurrence of -* from the make.conf. With -D with include
-* to the end of the USE setting in make.conf if a -* is already present. If
not it'll put a -* at the beginning of USE. If it is confusing, try it to find
out.
So this is how you use it:
# euse -E mozilla alsa all
Case 1:
If before executing this command the USE in make.conf looks like this:
USE="-* tiff -mozilla doc -alsa"
After executing it becomes:
USE="tiff mozilla doc alsa"

# euse -D mozilla alsa all
If before executing this command the USE in make.conf looks like this:
USE="tiff mozilla doc alsa"
After executing it becomes:
USE="-* tiff -mozilla doc -alsa"

Note: 
1. -E and -D flags can be used together like:
# euse -D mozilla -E alsa
To enable alsa and disable mozilla in the same command.


Author's Note
=============
If you have any comments(both good and bad) about the code or any features in
this program feel free to mail be codebear@gentoo.org.


Enjoy!!
                                                                        --Arun