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The correct choice is (d) $?

Explanation: The exit STATUS of a command is that particular value which is returned by the command to its PARENT. This value is STORED in $?.

Correct choice is (c) $* STORES the number of arguments specified

For EXPLANATION: The shell uses << symbol to read data from the same file containing the SCRIPT. This is referred to as a here document. read command allows us to TAKE input from the user to make the script interactive. && and || are logical operators which allow conditional execution. $* stores the complete set of positional parameters as a single string.

Correct choice is (B) -x

To explain I would say: As we know that set command is used for ASSIGNING values to POSITIONAL parameters, it also serves as debugging tool. For this purpose, we’ve to USE -x OPTION with it.

Correct choice is (d) mailx

Best EXPLANATION: The mailx command doesn’t ACCEPT any filename as its ARGUMENT. So if we want to give input to the mailx command, we can use the here document.

The CORRECT choice is (a) True

The best explanation: MANY commands require input from the user. So we can USE the here document with interactive programs also. In this MANNER, we can instruct any script to take the input non-interactively by supplying the input using the here document. For example,

Right ANSWER is (d) TRAP

For explanation I would say: Any shell script is terminated when the interrupt key is PRESSED. But this is not the appropriate way of doing so. For interrupting any program we should USE the trap command.

Correct option is (a) True

Easiest explanation: The shell USES >> SYMBOL to read data from the same file CONTAINING the script. This is referred to as a here DOCUMENT. It ALLOWS any command (which uses standard input) to take input from it.

The CORRECT option is (b) <<

Easy explanation: It may happen that the data our program wants to read is fixed and limited. The shell uses << symbol to read data from the same file containing the script. This is REFERRED to as a here document, SIGNIFYING that the data is here rather than in a separate file.

Correct answer is (b) —

For EXPLANATION I would say: set statement can also be used for command substitution. There can be a PROBLEM especially when the OUTPUT of the command BEGINS with a-.It may happen that set INTERPRETS it as an option. To avoid this condition, we have to use — (double hyphen) immediately after set. For example,

The correct CHOICE is (c) set

For EXPLANATION I would say: set statement is an INTERNAL command which assigns its ARGUMENTS to POSITIONAL parameters $1, $2 and so on. While cut, Is and expr are external commands.

Correct answer is (B) shift

Explanation: shift statement TRANSFERS the content of a positional parameter to its IMMEDIATE lower numbered one. This PROCESS continues as many times as shift is invoked. For example, when CALLED once, $2 becomes $1 and $3 becomes $2 and so on.

Right choice is (a) set

The EXPLANATION: set statement is an internal command which assigns its ARGUMENTS to POSITIONAL PARAMETERS $1, $2 and so on. For EXAMPLE, the following command will assign the value 1345 to $1 and 5678 to $2,

The correct option is (c) basename

To EXPLAIN I WOULD say: basename command is used for changing the extensions of a group of FILENAMES. It EXTRACTS the “base” filename from an absolute filename. For EXAMPLE,

Correct option is (a) True

Easy EXPLANATION: SHELL also offers an until statement which operates with a reverse logic USED in while. With until the loop body is executed as LONG as the condition REMAINS false.

The correct choice is (d) for, while, until

To ELABORATE: For REPEATEDLY performing a set of instructions, we have to use loops. Shell features THREE TYPES of loops —while, for and until. All of them repeat the INSTRUCTION set enclosed by certain keywords.

Right answer is (a) True

The explanation: expr command can ALSO locate the first OCCURRENCE of character INSIDE a string. For example, to locate the POSITION of character d in the string ‘abdullah’, we have to COUNT the number of characters which are not ‘d’ ([^d]*),

Right OPTION is (B) \(. .\)

To elaborate: expr can extract a substring enclosed by the escaped characters \ ( and \). For example, to extract ‘03’ from the string 2003 USE the following command:

The CORRECT option is (C) .*

For explanation: The length of the string can be extracted using .* . This regular expression signifies to EXPR that it has to display the number of characters MATCHING the pattern i.e. the length of the ENTIRE string. For example,

Correct OPTION is (a) True

Explanation: For EVALUATING strings expr uses two expressions separated by a colon. The STRING to be worked upon is PLACED on the left of the colon while a REGULAR expression is placed on its right.

Correct ANSWER is (d) DETERMINE the length of string, extract and locate the position of the string

To explain I would say: Though EXPR’s string handling features are not that elegant, bourne shell users HARDLY have any choice. For evaluating strings expr USES two expressions separated by a colon.

The CORRECT CHOICE is (c) 5

Easiest explanation: expr command can perform four basic ARITHMETIC operations as well as the modulus function. For EXAMPLE,

Correct choice is (a) expr

The explanation: The bourne shell can CHECK whether an integer is greater than ANOTHER or not, but it doesn’t have any COMPUTING features at all. It has to RELY totally on expr command for that PURPOSE. This command performs two functions:

•Performs arithmetic operations on integers

•Manipulates strings

The correct CHOICE is (a) True

To explain: CASE statement can also specify the same action for more than one pattern. Suppose, a PROGRAMMER wants to develop a logic for both Y or y (or N or n), then he/she can MAKE use of the case statement in the following MANNER:

Right answer is (a) True

Explanation: CASE statement has SUPERB string matching feature that uses wildcards. It uses the filename matching meta-characters *, ? and the CHARACTER class for matching STRINGS.

The correct answer is (c) ;;

To elaborate: case STATEMENT MATCHES an expression for more than ONE ALTERNATIVE. Every pattern in the case statement is TERMINATED with a ;; .

Correct option is (d) case

Explanation: The case statement is the second conditional offered by the shell. This statement MATCHES an EXPRESSION for more than one ALTERNATIVE. case statements are used in menu-driven PROGRAMS. The syntax of the case statement is:

case expression in

Correct choice is (a) True

Explanation: If we have two files namely FILE01 and FILE02 and we WANT to CHECK if file01 is LINKED with file02, we have to use -ef option with test. The syntax is file01 -effile02.

Right option is (d) -ot

Easiest explanation: If we have two file namely file01 and file02 and we WANT to CHECK if file01 is older than file02, we have to USE -ot option with test. The syntax is file01 -otfile02. Similarly, to check whether file01 is newer than file02 we’ve to use -nt option. These COMMANDS work in korn and bash shell only.

The CORRECT choice is (a) True

Easy explanation: If we WANT to check whether the file exists and is a DIRECTORY we have to use the -d OPTION. The syntax is -d filename.

The correct answer is (c) -x

Easiest explanation: If we want to check whether the file exists and is EXECUTABLE we have to USE the -x option. The syntax is -x FILENAME.

The correct OPTION is (d) -W

For EXPLANATION I would say: To check if the FILE exists and is writable we can use -w option. The syntax is -w filename.

The correct choice is (a) -R

The best I can EXPLAIN: To CHECK if the file EXISTS and is readable we can use -r OPTION. The syntax is -r filename.

Right option is (a) -e

Best explanation: test can ALSO be used to test the various file ATTRIBUTES like its type (ordinary, regular or symbolic LINK). To CHECK whether the file EXISTS or not, we can use the -e option. For example,

Correct answer is (a) True

Explanation: test can also be used to test the various FILE attributes LIKE its TYPE (ordinary, regular or symbolic link) or its PERMISSIONS (read, write, execute, etc).

The correct choice is (c) -z

For explanation I WOULD SAY: test can be used to compare STRINGS with another set of OPERATORS. -z is used for checking if the STRING is null. For example,

The correct ANSWER is (b) -a

The explanation is: test also permits the CHECKING of more than ONE condition in the same LINE using -a (AND) operator. For EXAMPLE,

The correct choice is (d) -n

For EXPLANATION I would say: TEST can be USED to compare strings with ANOTHER set of operators. -n is used for checking if the STRING is not null. For example,

Correct choice is (a) -o

For explanation I would say: TEST ALSO permits the CHECKING of more than one condition in the same line using -o (OR) operator. For example,

Correct choice is (a) True

To EXPLAIN I would say: We must provide whitespaces AROUND the operators (LIKE -eq), their operands (like $x) and inside the [ and ].

Right option is (a) True

To elaborate: test can be used to compare strings with another set of OPERATORS (LIKE = for EQUALITY of strings and != for inequality). For example, [ ! -z$string ] negates [ -z$string ].

Right choice is (b) [ ]

For explanation: UNIX PROVIDES a shorthand for test i.e. [ ]. We can use this PAIR of rectangular brackets enclosing the EXPRESSION. THUS the following two are equal,

Correct CHOICE is (b) False

Easiest EXPLANATION: Every numerical comparison operator used by the test BEGIN a hyphen, followed by a TWO letter string and enclosed by a WHITESPACE on either side.

Correct choice is (B) gt, lt

To EXPLAIN: There are some COMPARISON operators which are used by test. For example,

gt implies greater than, lt implies less than, LE implies less than or equal to, ge implies greater than or equal to.

The CORRECT choice is (d) –eq and -ne

To EXPLAIN: There are some comparison operators which are USED by test. For EXAMPLE,