Here is a listing of Linux / Unix Technical Interview Questions & Answers for experienced IT professionals as well as fresh engineering graduates. These questions can be attempted by anyone focusing on Linux Development and Systems programming.
1. Given a code snippet below?
#define PERMS (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)
int main()
{
int fd1, fd2;
umask(0);
fd1 = open(“file1”, O_CREAT | O_RDWR, PERMS)
umask(S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
fd2 = open(“file2”, O_CREAT | O_RDWR, PERMS)
return 0;
}
The newly created files file1 and file2 will have the permissions respectively
a) rw-rw-rw- r——–
b) r——– rw-rw-rw-
c) rw-rw-rw- rw——-
d) None of the mentioned
Answer: c
Clarification: None.
2. Below is the code
int main()
{
int fd1, fd2;
struct stat buff1, buff2;
fd1 = open(“1.txt”, O_RDWR);
fd2 = open(“2.txt”, O_RDWR | O_APPEND);
lseek(fd1, 10000, SEEK_SET);
write(fd1, “abcdefghij”, 10);
write(fd2, “abcdefghij”, 10);
fstat(fd1, &buff1);
fstat(fd2, &buff2);
printf(“ %d %d”, buff1.st_size, buff2.st_size);
return 0;
}
Before running the program, the file 1.txt and 2.txt size is 20 each. What is the output?
a) 30 30
b) 100020 20
c) 100030 30
d) 100010 30
Answer: d
Clarification: None.
3. What is stored in logfile as per below mentioned code if we execute ./a.out > logfile?
int main()
{
int fd;
close(1);
fd = open(“logfile”,O_RDWR, 0744);
write(fd, “Hello”, 5);
printf(“Worldn”);
return 0;
}
a) Hello
b) HelloWorld
c) World
d) None
Answer: b
Clarification: None.
4. For the below mentioned code,
int main()
{
int fd;
fd = open(“logfile”, O_CREAT|O_RDWR, 0600);
lseek(fd, 5, SEEK_CUR);
write(fd, “Hello”, 5);
return 0;
}
What is the logfile size now if it’s initially was 1024 bytes?
a) 5
b) 1024
c) 1029
d) 1034
Answer: b
Clarification: None.
5. Code snippets
str1=”45678n”
str2=”123n”
f1 = fopen(file1,RDWR,RWX)
f2 = fopen(file1,RDWR,RWX)
write(f1,str1,len_str1)
write(f2,str2,len_str2)
o/p:
a) 12378
b) 123(newline)8(newline)
c) 123(newline)78(newline)
d) 45678(newline)123(newline)
Answer: b
Clarification: None.
6. Code snippets
str1=”45678n”
str2=”123n”
f1 = fopen(file1,RDWR,RWX)
f2 = dup(f1)
write(f1,str1,len_str1)
write(f2,str2,len_str2)
o/p:
a) 12378
b) 123(newline)8(newline)
c) 123(newline)78(newline)
d) 45678(newline)123(newline)
Answer: d
Clarification: None.
7. Code snippet (file1 size is 2024)
f1 = fopen (file1, RDWR, RWX)
lseek(f1,1024,SEEK_SET)
write(f1,buf,10)
What is offset now.
a) 1024
b) 1034
c) 2034
d) 2054
Answer: b
Clarification: None.