Homework SourseIn Bash Shell Assume the command and output below echo PS1 g
In Bash Shell
Assume the command and output below:
echo $PS1
general >
Give the printout of the following sequential commands. Be sure to write “nothing” if the only thing appearing on the screen is the next prompt. Be sure to write “blank line” if a blank line is printed.
general > i=class; j=is; k=over
Nothing
general > echo $i $j $k
Class is over
general > sh
! general > echo $i $j $k
! general > i=Be; j=nice
! general > exit
general > echo $i $j $k
general > sh
! general > echo $i $j $k
! general > export i j
! general > i=enjoy; j=this
! general > echo $i $j $k
! general > exit
general > echo $i $j $k
general > export i j k
general > sh
! general > echo $i $j $k
! general > export i j
! general > i=enjoy; j=this
! general > sh
!! general > echo $i $j $k
!! general > exit
! general > exit
general > echo $i $j $k
Solution
Output of given sequential commands is mentioned in table below along with explanation.
| S.No. | Command | Output | Explanation |
| 1 | i=class; j=is; k=over | Nothing | As i, j, k are successfully set without any error (in say, shell1) |
| 2 | echo $i $j $k | class is over | As per values set for i, j, k in current bash shell (shell1) |
| 3 | sh | Nothing | As new shell instance is created (say, shell2) |
| 4 | echo $i $j $k | Blank line | As i, j, k are not initialized in newly created shell instance (shell2) |
| 5 | i=Be; j=nice | Nothing | As i, j are successfully set without any error (shell2) |
| 6 | exit | Nothing | As newly created shell instance (i.e. shell2) is destroyed and previous bash shell (shell1) is returned |
| 7 | echo $i $j $k | class is over | As per values set for i, j, k earlier in the bash shell returned (shell1) |
| 8 | sh | Nothing | As new shell instance is created (shell3) |
| 9 | echo $i $j $k | Blank line | As i, j, k are not initialized in newly created shell instance (shell3) |
| 10 | export i j | Nothing | As i, j variables export attribute is set |
| 11 | i=enjoy; j=this | Nothing | As i, j are successfully set without any error (shell3) |
| 12 | sh | Nothing | As another new shell instance is created (say, shell4) |
| 13 | echo $i $j $k | enjoy this | As values of only exported variables i, j are printed |
| 14 | exit | Nothing | As newly created shell instance (i.e. shell4) is destroyed and previous shell (shell3) is returned |
| 15 | exit | Nothing | As shell3 is destroyed and previous bash shell (shell1) is returned |
| 16 | echo $i $j $k | class is over | As per values set for i, j, k earlier in the bash shell returned (shell1). Note that variables exported in child shell are not propogated to parent shell. |
