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¥Some OS Commands
_  ls    : list the contents of a directory
_* cat   : concatenate files to the terminal (print them to the screen)
_* more  : a file perusal program - view files one page at a time
_* less  : a better file perusal program (type less, get more)
_  man   : on-line manuals for many OS commands (and library functions)
_           - this uses a "less" interface to display the information
_           - e.g. consider man on : ls, less, man, tcsh, afni
_  info  : a new program to replace the "man" program
_* head  : display the top lines of a file (default = 10)
_          - e.g.  3dDeconvolve -help | head -25
_* tail  : display the bottom lines of a file (default = 10)
_          - e.g.  tail ideal_r1.1D
_* wc    : word count - count characters, words and lines (of a file)
_  rm    : BE CAREFUL - remove files and/or directories (no recovery)
_          - e.g.  rm junk.file
_          - e.g.  rm -r bad.directory
_
_*   denotes a 'filter' program, which can take input from a file or from stdin