Operational Debugging Interview Preparation Guide
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Linux Debugging frequently Asked Questions by expert members with experience in Debugging. These questions and answers will help you strengthen your technical skills, prepare for the new job test and quickly revise the concepts

80 Linux Debugging Questions and Answers:

1 :: Which one of the following command saves the command history of GDB in a file?
a) history
b) set history
c) set history save on
d) none of the mentioned

c) set history save on

2 :: In GDB, a trace-point can be set by the command
a) trace
b) set
c) break trace
d) none of the mentioned

a) trace

3 :: The command "show commands" of GDB
a) displays the last 10 commands in the command history
b) displays all commands of the command history
c) displays all the commands available in GDB
d) none of the mentioned

a) displays the last 10 commands in the command history

4 :: The GDB command "show output-radix"
a) sets the default base for numeric display
b) displays the current default base for numeric display
c) both (a) and (b)
d) none of the mentioned

b) displays the current default base for numeric display

5 :: The user can define a command for GDB with the command:
a) define
b) command
c) assign
d) none of the mentioned

a) define

6 :: By default the GDB automatically executes the command from its:
a) init files
b) start files
c) begin files
d) none of the mentioned

a) init files

7 :: The GDB text user interface uses the ____ library to show the source file.
a) curses
b) YUI
c) JUI
d) none of the mentioned

a) curses

8 :: Which one of the following GDB command allows to move from one stack frame to another without printing the frame?
a) select-frame
b) frame
c) frame move
d) none of the mentioned

a) select-frame

9 :: Which one of the following GDB command deletes any break-point at the next instruction to be executed in the selected stack frame?
a) clear
b) delete
c) disable
d) none of the mentioned

a) clear

10 :: The result of an expression can be assigned to an environment variable with the command:
a) assign
b) set
c) env
d) none of the mentioned

b) set

11 :: In GDB hardware-dependent information about the floating point unit can be displayed by the command
a) info float
b) display float
c) show float
d) none of the mentioned

a) info float

12 :: In GDB, we can refer to machine register contents, in expressions, as variables with names starting with:
a) $
b) #
c) !
d) none of the mentioned

a) $

13 :: Which one of the following variables is used within GDB to hold on to a value and refer to it later?
a) convenience variables
b) environment variables
c) temporary variables
d) none of the mentioned

a) convenience variables

14 :: If we want to print the value of a variable in hexadecimal, we have to use "print" command with the option ___ in GDB.
a) x
b) h
c) hex
d) none of the mentioned

a) x

15 :: In GDB which one of the following allows us to specify a variable in terms of the file or function where it is defined?
a) ::
b) @
b) $
d) none of the mentioned

a) ::

16 :: With the list command, by default GDB prints the ____ source lines.
a) 20
b) 10
c) all
d) none of the mentioned

b) 10

17 :: Which one of the following is a special breakpoint that stops the program when the value of an expression changes in GDB?
a) watchpoint
b) catchpoint
c) getpoint
d) none of the mentioned

a) watchpoint

18 :: Inside GDB, a program may stop because of
a) a signal
b) a breakpoint
c) step command
d) all of the mentioned

d) all of the mentioned

19 :: While debugging with GDB, arguments to the program can be specified by the arguments of _____ command.
a) run
b) gdb
c) make
d) none of the mentioned

a) run

20 :: What is the output of this program no 16?
#include<stdio.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<sys/socket.h>
#include<errno.h>

int main()
{
struct sockaddr_in addr;
int fd;
fd = socket(AF_UNIX,SOCK_STREAM,0);
if (fd == -1)
perror("socket");
addr.sun_family = AF_UNIX;
strcpy(addr.sun_path,"san_sock");
if (bind(4,(struct sockaddr*)&addr,sizeof(addr)) == -1)
printf("Sanfoudnryn");
return 0;
}
a) error
b) "google"
c) segmentation fault
d) none of the mentioned

a) error
Explanation:
The structure used for AF_UNIX if sockaddr_un.
Output:
[root@localhost google]# gcc -o san san.c
san.c: In function 'main':
san.c:14:6: error: 'struct sockaddr_in' has no member named 'sun_family'
san.c:15:2: warning: incompatible implicit declaration of built-in function 'strcpy' [enabled by default]
san.c:15:13: error: 'struct sockaddr_in' has no member named 'sun_path'
[root@localhost google]#

21 :: What is the output of this program no 15?
#include<stdio.h>
#include<sys/types.h>
#include<sys/un.h>
#include<sys/socket.h>

int main()
{
struct sockaddr_un add_server, add_client;
int fd_server, fd_client;
int len;
char ch;
fd_server = socket(AF_UNIX,SOCK_STREAM,0);
if(fd_server == -1)
perror("socket");
add_server.sun_family = AF_UNIX;
strcpy(add_server.sun_path,"san_sock");
if( bind(fd_server,(struct sockaddr)&add_server,sizeof(add_server)) != 0)
perror("bind");
len = sizeof(add_client);
fd_client = connect(fd_server,(struct sockaddr)&add_client,&len);
printf("googlen");
return 0;
}
a) this program will print the string "google"
b) segmentation fault
c) error
d) none of the mentioned

c) error
Explanation:
The syntax of the connect() is wrong. connect() should be used in client program only.
Ouptut:
[root@localhost google]# gcc -o san san.c
san.c: In function 'main':
san.c:20:46: warning: passing argument 3 of 'connect' makes integer from pointer without a cast [enabled by default]
/usr/include/sys/socket.h:129:12: note: expected 'socklen_t' but argument is of type 'int *'
[root@localhost google]#

22 :: What this program is not able to connect with any client program?

#include<stdio.h>
#include<sys/types.h>
#include<sys/un.h>
#include<sys/socket.h>

int main()
{
struct sockaddr_un add_server, add_client;
int fd_server, fd_client;
int len;
char ch;
fd_server = socket(AF_UNIX,SOCK_STREAM,0);
if(fd_server == -1)
perror("socket");
add_server.sun_family = AF_UNIX;
strcpy(add_server.sun_path,"san_sock");
if( bind(fd_server,(struct sockaddr)&add_server,sizeof(add_server)) != 0)
perror("bind");
len = sizeof(add_client);
fd_client = accept(fd_server,(struct sockaddr)&add_client,&len);
printf("googlen");
return 0;
}
a) the listen() is missing
b) the connect() is missing
c) the read() and write() are missing
d) none of the mentioned

a) the listen() is missing

23 :: What is the output of this program no 14?
#include<stdio.h>
#include<sys/types.h>
#include<sys/un.h>
#include<sys/socket.h>
#include<errno.h>

int main()
{
struct sockaddr_un addr;
int fd;
fd = socket(AF_UNIX,SOCK_STREAM,0);
if (fd == -1)
perror("socket");
addr.sun_family = AF_UNIX;
strcpy(addr.sun_path,"san_sock");
if (bind(4,(struct sockaddr*)&addr,sizeof(addr)) == -1)
printf("Sanfoudnryn");
return 0;
}
a) this program will print the string "google"
b) this program will not print the string "google"
c) segmentation fault
d) none of the mentioned

a) this program will print the string "google"
Explanation:
The first argument of the bind() is not a valid file descriptor in this program.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
Sanfoudnry
[root@localhost google]#

24 :: What is the output of this program?

#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>

int main()
{
int fd;
fd = socket(AF_UNIX,SOCK_STREAM,0);
printf("%dn",fd);
return 0;
}
a) 0
b) 1
c) 2
d) 3

d) 3
Explanation:
The socket() returns the lowest available file descriptor and in this program i.e. 3.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
3
[root@localhost google]#

25 :: What is the output of the program no 13?

#include<stdio.h>
#include<sys/types.h>
#include<sys/un.h>
#include<sys/socket.h>

int main()
{
struct sockaddr_un add_server, add_client;
int fd_server, fd_client;
int len;
char ch;
fd_server = socket(AF_UNIX,SOCK_STREAM,0);
if(fd_server == -1)
perror("socket");
add_server.sun_family = AF_UNIX;
strcpy(add_server.sun_path,"san_sock");
if( bind(fd_server,(struct sockaddr)&add_server,sizeof(add_server)) != 0)
perror("bind");
if( listen(fd_server,3) != 0)
perror("listen");
len = sizeof(add_client);
fd_client = accept(fd_server,(struct sockaddr)&add_client,&len);
printf("googlen");
return 0;
}

a) the program will print the string "google"
b) the process will remain block
c) segmentation fault
d) none of the mentioned

b) the process will remain block
Explanation:
There is no peding request in the queue for listening socket "san_sock".
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
^Z
[4]+ Stopped ./san
[root@localhost google]#

80 Linux Debugging Interview Questions and Answers

Operational Debugging Interview Preparation Guide Download PDF

80 Linux Debugging Questions and Answers:

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Operational Debugging Interview Preparation Guide
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