I see that my programs install to usr/local/bin and that I can change that if I do ./configure --prefix=/usr/ at the build. Where is the default prefix specified? Where can I change the default? Is it possible to change the default installation to /usr/bin/ for my program only instead of changing the default for the user?
Where is installation prefix set?
software installation;compiling;configure
Installing locally built applications with prefix /usr is a really bad idea as the files installed may easily overwrite files installed by package managers.  This may later give you issues if the package managers gets confused when file checksums no longer match, or when there are mismatches between executables and libraries./usr/local is the correct place to install locally compiled software on most systems, although /opt may be a safer (most BSD Unices uses /usr/local for third party software).I would definitely not recommend trying to change the default prefix.Having said that, it is defined in the file general.m4 in the autoconf distribution as the variable as_default_prefix. On my OpenBSD system, this file resides in /usr/local/share/autoconf-2.69/autoconf. This directory may be located elsewhere if you're on Linux or use another version of autoconf.This variable would have to be changed in the autoconf distribution and any configure script would have to be re-generated (as this variable is inserted in the configure script by autoconf when it's created).An easier way would be to create a config.site file as described in the autoconf documentation and set the value of prefix.Again, changing this would most definitely lead to shooting yourself in the foot further down the line.See also: Filesystem Hierarchy Standard.