OS515-Workbook6-part2

Question 1

The bash shell expands certain command line metacharacters before…?

Answer 1

interpreting the command.

Question 2

Tilde expansion expands tokens that begin with a…?

Answer 2

tilde (~) to users home directories.

Question 3

Brace expansion expands tokens with …?

Answer 3

braces ({}) into multiple words, each of which contains a single word from the specified list.

mkdir {dir1,dir2,dir3}/{subdir1,subdir2}

mkdir dir1
mkdir dir1/subdir1
mkdir dir1/subdir2
…etc…

Question 4

Command substitution expands text enclosed within…?

Answer 4

backticks (‘’) or “dollar parenthesis” ($()) into the output produced by the enclosed command.

VAR=COMMAND

FILES=`ls /etc`
FILES=$(ls /etc)

Question 5

Pathname Expansion ("File Globbing")
Covered earlier and is also...?

Answer 5

a shell expansion.

Question 6

Remember that expansion occurs before the program is…?

Answer 6

executed, so the program is given a set of matching files.

Question 7

Pathname Expansion:

Character * match?

Answer 7

0 or more characters

Question 8

Pathname Expansion:

Character ? match?

Answer 8

Exactly one characters.

Question 9

Pathname Expansion:

Character […] match?

Answer 9

Exactly one of the included characters.

Question 10

Pathname Expansion:

Character [^…]

Answer 10

Exactly one of the excluded characters.

Question 11

See slide 8 for…?

Answer 11

command line expansion subtleties.

Question 12

The bash shell internally implements certain simple commands which are closely related to the…?

Answer 12

to the shell’s behavior. These are referred to as builtin commands.

Question 13

Shell aliases create apparent commands which…?

Answer 13

expand to arbitrary text.

Question 14

The bash shell prompt can be…?

Answer 14

customized using the PSI variable.

Question 15

Shell flags modify the …?

Answer 15

bash shell behavior.

Question 16

Shell options offer more…?

Answer 16

bash shell configuration options.

Question 17

Slide 11 shows…?

Answer 17

Slide Builtins.

Question 18

Slide 12 shows…?

Answer 18

Aliases

Question 19

Running commands.

Answer 19

Perform any shell expansions
v
Expand any aliases
v
If command is shell function, run the function.
v
If the command is built-in run it.
v
if the command is absolute run it (if allowed and exists)
v
Search PATH for command if allowed run it.

Question 20

PS1…?

Answer 20

Default prompt.

Question 21

PS2…?

Answer 21

Secondary prompt.

Question 22

Sequence \a expansion?

Answer 22

audible terminal bell.

Question 23

Sequence \d expansion?

Answer 23

date in “Weekday Month Date” format.

Question 24

Sequence \h expansion?

Answer 24

the hostname up to the first “.”

Question 25

Sequence \T expansion?

Answer 25

the current time in 12-hour HH:MM:SS format

Question 26

Sequence \u expansion?

Answer 26

the username of the current user.

Question 27

Sequence \W expansion?

Answer 27

the basename of the current working directory.

Question 28

Sequence \! expansion?

Answer 28

the history number of this command.

Question 29

Sequence \$ expansion?

Answer 29

if the effective UID is 0, a #, otherwise a $.

Question 30

Sequence \nnn expansion?

Answer 30

the character corresponding to the octal number nnn.

Question 31

Shell Flags: The set Builtin Command: | Flag -f and its effect...?

Answer 31

Disable Pathname Expansion (Globbing)

Question 32

Shell Flags: The set Builtin Command: | Flag -n and its effect...?

Answer 32

Read commands, but do not execute them (used for performing syntax checks on scripts).

Question 33

Shell Flags: The set Builtin Command: | Flag -o optionname and its effect...?

Answer 33

Set the specified option. Some of the more common options include the following. emacs Use emacs style command line key bindings ignoreeof Do not exit shell when EOF (CTRL-D) is read vi Use vi style command line key bindings

Question 34

Shell Flags: The set Builtin Command: | Flag -v and its effect...?

Answer 34

Print commands as they are read (useful in debugging scripts)

Question 35

Shell Flags: The set Builtin Command: | Flag -x and its effect...?

Answer 35

Print commands after expansions have been applied (useful in debugging scripts and examining shell expansions)

Question 36

Shell Flags: The set Builtin Command: | Flag -C and its effect...?

Answer 36

Don't allow the shell to clobber files on redirection.

Question 37

Shell Flags: The set Builtin Command: | Examples...?

Answer 37

[madonna@station madonna]$ set -f [madonna@station madonna]$ ls /etc/*.conf ls: /etc/*.conf: No such file or directory [madonna@station madonna]$ set +f [madonna@station madonna]$ ls /etc/*.conf /etc/aep.conf /etc/lftp.conf /etc/pnm2ppa.conf

Question 38

Shell Options: The shopt Builtin Command: | Option cdspell and its effect...?

Answer 38

Attempt to correct minor misspellings of directory names when using the cd builtin command.

Question 39

Shell Options: The shopt Builtin Command: | Option expand_aliases and its effect...?

Answer 39

Enable shell aliases.

Question 40

Shell Options: The shopt Builtin Command: | Option extglob and its effect...?

Answer 40

Enable extended globbing pattern matching syntax.

Question 41

Shell Options: The shopt Builtin Command: | Option nocaseglob and its effect...?

Answer 41

Do not consider case when applying file globbing.

Question 42

Shell Options: The shopt Builtin Command: | Examples...?

Answer 42

``` [madonna@station madonna]$ shopt cdspell cdspell off [madonna@station madonna]$ shopt -s cdspell [madonna@station madonna]$ cd /ect /etc [madonna@station etc]$ ls -d /ect ls: /ect: No such file or directory [madonna@station etc]$ shopt -u cdspell [madonna@station etc]$ cd /ect -bash: cd: /ect: No such file or directory ```

Question 43

Shell scripts are sourced with the ...?

Answer 43

source or . commands.

Question 44

Shell scripts are all executed in the same shell that...?

Answer 44

sources the script.

Question 45

See slide 19 for ...?

Answer 45

bash initialization.