Unix Variable Assignment Environment Essay Introduction
So an “Undefined variable” error means that the given variable has not been set (maybe a typo, maybe a logic error).
These are the variables which are created and maintained by Operating System(Linux) itself.
Generally these variables are defined in CAPITAL LETTERS.
The only special thing here is a deviation from Unix-land to AFNI-land. commands (type these in the terminal window): We start from AFNI_data6 for convenience, and set a subject ID variable to FT. The ‘ls’ command should produce the error: However ‘3dinfo $anat_dset’ works fine, because AFNI programs do not need the complete filename, just the prefix (FT_anat) and view ( orig).
Then we get a listing of the contents of that subject’s data directory. So anat_dset is set to the name of that AFNI dataset, including the dataset prefix and view, but not the file extension. commands (type these in the terminal window): command should show ‘FT_analysis/FT/FT_anat orig’, but the subsequent ‘ls -l’ command should fail, because there is no actual file of that name (the files end in either . The output is text describing the dataset (location in space, resolution, command history, etc). commands (type these in the terminal window): Next, an echo command merely appends .