What does the + symbol mean in the following grep regular expression: <code> grep ‘^d[aei]\+d$’ /usr/share/dict/words </code>
Which option to the tee command will cause the output to be concatenated on the end of the output file instead of overwriting the existing file contents?
Which of the following shell redirections will write standard output and standard error output to a file named filename?
Which of the following explanations are valid reasons to run a command in the background of your shell?