Question

What is the result of the command ?

$ who | grep $USER

$ grep \$HOME economics1

$ echo u*>> economics1

$ echo ‘u*’ >> economics1

$ . economicsA

$ set noclobber

$ set -o

$ chmod +x economics2

$ spell < economics1

economic is file name

linux command

Answer 1

who | grep $USER

who -shows who is log on

grep \$HOME economics1

show lines matching pattern

echo u*>> economics1
bash: economics1: Is a directory

echo ‘u*’ >> economics1
bash: economics1: Is a directory

. economicsA

shows is directory or not

set noclobber

When setting 'noclobber' overwriting the content of an existing file by the '>' redirection operator will not be possible. You might have typed '>' to redirect the output of a certain command to an existing file, while you intended to use '>>' redirection operator. This is where 'noclobber' comes in action, preventing you from accidentally deleting the content of the existing file.

set -o

-o option-name
          Set the variable corresponding to option-name:
              allexport    same as -a
              braceexpand same as -B
              emacs        use an emacs-style line editing interface
              errexit      same as -e
              errtrace     same as -E
              functrace    same as -T
              hashall      same as -h
              histexpand   same as -H
              history      enable command history
              ignoreeof    the shell will not exit upon reading EOF
              interactive-comments
                           allow comments to appear in interactive commands
              keyword      same as -k
              monitor      same as -m
              noclobber    same as -C
              noexec       same as -n
              noglob       same as -f
              nolog        currently accepted but ignored
              notify       same as -b
              nounset      same as -u
              onecmd       same as -t
              physical     same as -P
              pipefail     the return value of a pipeline is the status of
                           the last command to exit with a non-zero status,
                           or zero if no command exited with a non-zero status
              posix        change the behavior of bash where the default
                           operation differs from the Posix standard to
                           match the standard
              privileged   same as -p
              verbose      same as -v
              vi           use a vi-style line editing interface
              xtrace       same as -x

chmod +x

changes file permissions and set it to

allow executing as program

spell < economics1

prints the miss spell world in file