Bash: Piping Text

### piping crash course ###

var=`command`        # put output of 'command' into $var
var=$(command)       # same as above, but can be nested. Non-standard but works in major shells
command1 | command2  # feed standard output of 'command1' to standard input of 'command2'
command > file       # overwrite file 'file' with output of 'command'
command >>file       # append output of 'command' to file 'file'
command < file       # feed file 'file' to standard input of 'command'

# now, the handy "heredoc"
command << "MARKER"  # feed everything until MARKER (can be anything, traditionally it is EOF)
blah                 # to 'command'. this is useful in scripts where you want to give a program
blah                 # some input automatically without dequiring the user to type
MARKER               # :)

# the "pipe" | can be used with a variaty of UNIX programs, for example grep, sed, awk, head, tail and diff.
# redirecting output to a file ( >file ) can be used to supress output: command >/dev/null
#  (the UNIX pseudo-device /dev/null swallows all input and outputs only ASCII EOF)