Foo reads bar as stdin, pipes output to foobar-common redirection operators command >file : redirects standard output of command into the file command>>file : append the standard output of command into the file commandfile : redirects the standard error into the file and pipe (|) is used to combine the command, in piping outout of first command goes as input to the second command. answer a is correct because foo command takes input from the bar file and sends the standard output to foobar command.
