Linux

Linux-(Files and IPC)

1) Explain chmod and umask commands

Ans:

        a)  CHMOD: To change the existing file permission,we can change file permission to new permission or can change one permission alone.

                           eg:
                                 chmod 0664 file_name
                                    rwx   rwx     rxx
                                      user group  others

       b)  UMASK: When you create a file or directory, the default file permissions assigned to the file or directory are controlled by the user mask.

• To check the umask value type umask and press enter. This will shows octal value 0664
• umask -S this will shows in string  eg - rwx rwx rxx
• once we change the umask value then new creating files permission updated to umask value.

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2) Explain 5 members of stat structure.

Ans:

•      st_atime
•      st_mtime
•      st_ctime
•      st_size
•      st_mode

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3) Explain the prototypes of below functions
a) opendir() b) readdir() c)time() d) ctime() e)open()

Ans:

a) DIR *opendir(const char *name); Open directory

b) struct dirent *readdir(DIR *dirp); Read directory 

c)time_t time(time_t *t);                   Get the time in seconds

d)char* ctime(const time_t *t);         to change time into ASCII

e)int open(const char *pathname,int flags); to open files

   int open(const char *pathname,int flags,mode_t mode);

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4) Explain output and input redirection with one simple example.

Output redirection is STDOUT  redirect to a file

Input redirection is  STDIN  redirect to a file (Instead of keyboard, CPU will get data from file)

Prgm: Click here

Prgm header.h: Click here

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5) Why IPC required? Explain it.

IPC allows one process to control another process, so data sharing can do without any interference. by using this mechanism (PIPE, FIFO,MESSAGE QUEUE,SHARED MEMORY, SEMAPHORES)we can communicate one process to another process. IPC facilitates efficient data transfer between processes.

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6) WAP to create 3 child processes where parent need to put 15 bytes in pipe and all 3 child's need to read 5 bytes each and print.

Prgm : Click here

Prgm header.h: Click here

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7) p1 process need to send one structure to p2 which contain 2 operands and 1 operator. p2 need to do operation and send result to p1. P1 need to display result use FIFO (10 Marks)
Note: p1.c and p2.c two separate programs need to submit.

Prgm P1.c: Click here

Prgm P2.c: Click here

Prgm header.h: Click here

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8) p1 process need to get file info using stat() and put into shared memory and p2 process need to read and print any five members of that structure. (10 Marks).
Note: p1.c and p2.c two separate programs need to submit.

Prgm P1.c : Click here

Prgm P2.c : Click here

Prgm header.h: Click here

********************************Thank you!!!😊*************************************