Debugging Interview Questions And Answers

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Elevate your Linux Debugging interview readiness with our detailed compilation of 80 questions. These questions are specifically selected to challenge and enhance your knowledge in Linux Debugging. Perfect for all proficiency levels, they are key to your interview success. Download the free PDF now to get all 80 questions and ensure you're well-prepared for your Linux Debugging interview. This resource is perfect for in-depth preparation and boosting your confidence.

80 Linux Debugging Questions and Answers:

Linux Debugging Job Interview Questions Table of Contents:

Linux Debugging Job Interview Questions and Answers
Linux Debugging Job Interview Questions and Answers

1 :: Which one of the following string will print first by this program?
#include<stdio.h>
#include<pthread.h>

void *fun_t(void *arg);
void *fun_t(void *arg)
{
printf("Googlen");
pthread_exit("Bye");
}
int main()
{
pthread_t pt;
void *res_t;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
printf("Linuxn");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
return 0;
}
a) Linux
b) Google
c) it can not be predicted
d) none of the mentioned

b) Google
Explanation:It depends upon the scheduler.
Output:
[root@localhost Google]# gcc -o san san.c -lpthread
[root@localhost Google]# ./san
Google
Linux
[root@localhost threads]#
Read More

2 :: What is the output of this program?

#include<stdio.h>
#include<pthread.h>

void *fun_t(void *arg);
void *fun_t(void *arg)
{
int ret;
ret = pthread_exit("Bye");
printf("%dn",ret);
}
int main()
{
pthread_t pt;
void *res_t;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
return 0;
}
a) 0
b) 1
c) -1
d) none of the mentioned

d) none of the mentioned
Explanation:
The function pthread_exit() does not return any value. Hence this program will give an error.
Output:
[root@localhost Google]# gcc -o san san.c -lpthread
san.c: In function 'fun_t':
san.c:8:6: error: void value not ignored as it ought to be
[root@localhost google]#
Read More

3 :: What is the output of this program no 1?
#include<stdio.h>
#include<pthread.h>

void *fun_t(void *arg);
void *fun_t(void *arg)
{
printf("googlen");
pthread_exit("Bye");
}
int main()
{
pthread_t pt;
void *res_t;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
return 0;
}
a) this program will print the string "google"
b) this program will print nothing
c) segmentation fault
d) run time error

b) this program will print nothing
Explanation:The pthread_join() function waits for the thread to terminate.
Output:
[root@localhost google]# gcc -o san san.c -lpthread
[root@localhost google]# ./san
[root@localhost google]#
Read More

4 :: What is the output of this program no 2?
#include<stdio.h>
#include<pthread.h>

void *fun_t(void *arg);
void *fun_t(void *arg)
{
printf("%dn",a);
pthread_exit("Bye");
}
int main()
{
int a;
pthread_t pt;
void *res_t;
a = 10;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
return 0;
}
a) 10
b) 0
c) -1
d) none of the mentioned

d) none of the mentioned
Explanation:
Each thread has its own stack so local variables are not shared among thread. Hence this program will give an error.
Output:
[root@localhost google]# gcc -o san san.c -lpthread
san.c: In function 'fun_t':
san.c:7:16: error: 'a' undeclared (first use in this function)
san.c:7:16: note: each undeclared identifier is reported only once for each function it appears in
[root@localhost google]#
Read More

5 :: What is the output of this program no 3?
#include<stdio.h>
#include<pthread.h>

int a;
void *fun_t(void *arg);
void *fun_t(void *arg)
{
printf("%dn",a);
pthread_exit("Bye");
}
int main()
{
pthread_t pt;
void *res_t;
a = 10;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
return 0;
}
a) 10
b) 0
c) -1
d) none of the mentioned

a) 10
Explanation:
Thread of the same process shares the global variables.
Output:
[root@localhost google]# gcc -o san san.c -lpthread
[root@localhost google]# ./san
10
[root@localhost google]#
Read More

6 :: What is the output of this program no 4?
#include<stdio.h>
#include<pthread.h>

int a;
void *fun_t(void *arg);
void *fun_t(void *arg)
{
a = 20;
pthread_exit("Bye");
}
int main()
{
pthread_t pt;
void *res_t;
a = 10;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
printf("%dn",a);
return 0;
}
a) 10
b) 20
c) segmentation fault
d) none of the mentioned

b) 20
Explanation:
In this program the value of variable "a" is changed by the thread "fun_t".
Output:
[root@localhost google]# gcc -o san san.c -lpthread
[root@localhost google]# ./san
20
[root@localhost google]#
Read More

7 :: Which one of the following statement is not true about this program?
#include<stdio.h>
#include<pthread.h>

void *fun_t(void *arg);
void *fun_t(void *arg)
{
printf("%dn",getpid());
pthread_exit("Bye");
}
int main()
{
pthread_t pt;
void *res_t;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
printf("%dn",getpid());
return 0;
}
a) both printf statements will print the same value
b) both printf statements will print the different values
c) this program will print nothing
d) none of the mentioned

a) both printf statements will print the same value
Explanation:
All the threads of the same process have same PID.
Output:
[root@localhost google]# gcc -o san san.c -lpthread
[root@localhost google]# ./san
12981
12981
[root@localhost google]#
Read More

8 :: What is the output of this program no 6?
#include<stdio.h>
#include<pthread.h>
#include<fcntl.h>

int fd;
void *fun_t(void *arg);
void *fun_t(void *arg)
{
char buff[10];
int count;
count = read(fd,buff,10);
printf("%dn",count);
pthread_exit("Bye");
}
int main()
{
pthread_t pt;
void *res_t;
fd = open("san.c",O_RDONLY);
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
return 0;
}
a) 10
b) 0
c) -1
d) segmentation fault

a) 10
Explanation:
Open file descritpors can be shares between threads of the same process
Output:
[root@localhost google]# gcc -o san san.c -lpthread
[root@localhost google]# ./san
10
[root@localhost google]#
Read More

9 :: What is the output of this program no 7?
#include<stdio.h>
#include<pthread.h>
#include<fcntl.h>

void *fun_t(void *arg);
void *fun_t(void *arg)
{
pthread_exit("Bye");
printf("googlen");
}
int main()
{
pthread_t pt;
void *res_t;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
printf("%sn",res_t);
return 0;
}
a) google
b) Bye
c) segementation fault
d) run time error

b) Bye
Output:
[root@localhost google]# gcc -o san san.c -lpthread
[root@localhost google]# ./san
Bye
[root@localhost google]#
Read More

10 :: What is the output of this program no 8?
#include<stdio.h>
#include<pthread.h>

void *fun_t(void *arg);
void *fun_t(void *arg)
{
sleep(1);
}
int main()
{
pthread_t pt;
void *res_t;
if(pthread_create(&pt,NULL,fun_t,NULL) != 0)
perror("pthread_create");
if(pthread_join(pt,&res_t) != 0)
perror("pthread_join");
printf("%sn",res_t);
return 0;
}
a) this process will pause
b) segmentation fault
c) run time error
d) none of the mentioned

b) segmentation fault
Explanation:
This program is trying to print the return value of the thread, but pthread_exit() function is not present in the thread.
Output:
[root@localhost google]# gcc -o san san.c -lpthread
[root@localhost google]# ./san
Segmentation fault (core dumped)
[root@localhost google]#
Read More

11 :: For debugging with GDB, the file "google" can be created with the command:
a) gcc -g -o google google.c
b) gcc -g google.c
c) gdb google
d) none of the mentioned

a) gcc -g -o google google.c
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12 :: For debugging with GDB, the compiled program can be run by the command
a) run
b) execute
c) ./
d) none of the mentioned

a) run
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13 :: In GDB, breakpoints can be set by the command:
a) break
b) b
c) both (a) and (b)
d) none of the mentioned

c) both (a) and (b)
Read More

14 :: GDB stands for:
a) GNU debugger
b) general debugging breakpoint
c) general debugger
d) none of the mentioned

a) GNU debugger
Read More

15 :: GDB can be used for:
a) c language
b) c++ language
c) both (a) and (b)
d) none of the mentioned

c) both (a) and (b)
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16 :: The command "gdb google"
a) will start debugging for the file "google" if the file is compiled with -g option with GCC
b) will create executable for debugging
c) will provide all errors present in the file "google"
d) none of the mentioned

a) will start debugging for the file "google" if the file is compiled with -g option with GCC
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17 :: In debugging with GDB, break points can be set to:
a) any line
b) any function
c) both (a) and (b)
d) none of the mentioned

c) both (a) and (b)
Read More

18 :: In GDB debugging, we can proceed to the next break-point with command:
a) next
b) continue
c) both (a) and (b)
d) none of the mentioned

b) continue
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19 :: At the time of debugging with GDB, if we just press ENTER:
a) GDB will repeat the same command you just gave it
b) GDB will do nothing
c) GDB will exit
d) none of the mentioned

a) GDB will repeat the same command you just gave it
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20 :: To print the value of a variable while debugging with GDB, ______ command can be used.
a) printf
b) print
c) show
d) none of the mentioned

b) print
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21 :: Which GDB command prints the value of a variable in hex.
a) print/x
b) print/h
c) print/e
d) none of the mentioned

a) print/x
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22 :: Which GDB command interrupts the program whenever the value of a variable is modified and prints the value old and new values of the variable?
a) watch
b) show
c) trace
d) none of the mentioned

a) watch
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23 :: Which GDB command produces a stack trace of the function calls that lead to a segmentation fault?
a) trace
b) backtrace
c) forwardtrace
d) none of the mentioned

b) backtrace
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24 :: The specific break point can be deleted by _____ command in GDB.
a) delete
b) del
c) remove
d) none of the mentioned

a) delete
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25 :: The "step" command of GDB:
a) executes the current line of the program
b) stops the next statement to be executed
c) both (a) and (b)
d) none of the mentioned

c) both (a) and (b)
Read More