Linux Search Pattern Question: Download Search Pattern PDF

What is the output of this program?

#include<stdio.h>
#include<fcntl.h>

int main()
{
int fd, count;
char ch[10];
fd = open("google.txt",O_RDWR|O_CREAT);
write(fd,"linux",5);
lseek(fd,2,SEEK_END);
write(fd,"san",3);
lseek(fd,0,0);
count = read(fd,ch,10);
printf("%sn",ch);
return 0;
}
a) linux
b) linuxsan
c) linux san
d) none of the mentioned

Answer:

a) linux
Explanation:
The lseek function allows the file offset to be set beyond the end of the file and if the data is latter written this point, subsequent reads of the data in the gap returns NULL.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
linux
[root@localhost google]#

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What is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>

int main()
{
int fd, new_fd;
char *buff;
buff = (char *)malloc(sizeof(char)*8);
fd = open("san.c",O_RDONLY);
new_fd = dup(fd);
close(fd);
read(new_fd,buff,8);
printf("%sn",buff);
}
a) this program will not print anything
b) this program will print "#include"
c) this program will give the segmentation fault
d) this program will give the syntax error

Tell me what is the output of this program?

#include<stdio.h>
#include<fcntl.h>

int main()
{
int fd, count;
char ch;
fd = open("google.txt",O_RDWR|O_CREAT);
write(fd,"s",1);
lseek(fd,0,SEEK_SET);
write(fd,"d",1);
lseek(fd,0,0);
read(fd,&ch,1);
printf("%cn",ch);
return 0;
}
a) d
b) s
c) sd
d) none of the mentioned