Snippet 1: check_file_permissions.c #include

1

#include

#include

int main (int argc, char* argv[])

{ char* filepath = argv[1];

int returnval;

// Check file existence returnval = access (filepath, F_OK);

if (returnval == 0) printf (" %s exists ", filepath);

else { if (errno == ENOENT) printf ("%s does not exist ", filepath);

else if (errno == EACCES) printf ("%s is not accessible ", filepath);

return 0; }

// Check read access ...

// Check write access ...

return 0;

}

0. (a) Extend code snippet 1 to check for read and write access permissions of a given file

(b) Write a C program where open system call creates a new file (say, destination.txt) and then opens it. (Hint:

use the bitwise OR flag)

1. UNIX cat command has three functions with regard to text files: displaying them, combining copies of them

and creating new ones.

Write a C program to implement a command called displaycontent that takes a (text) file name as argument and display its contents. Report an appropriate message if the file does not exist or cant be opened (i.e. the file doesnt have read permission). You are to use open(), read(), write() and close() system calls.

NOTE: Name your executable file as displaycontent and execute your program as ./displaycontent file_name

2. The cp command copies the source file specified by the SourceFile parameter to the destination file specified

by the DestinationFile parameter.

Write a C program that mimics the cp command using open() system call to open source.txt file in read-only mode and copy the contents of it to destination.txt using read() and write() system calls.

3. Repeat part 2 (by writing a new C program) as per the following procedure:

(a) Read the next 100 characters from source.txt, and among characters read, replace each character 1

with character A and all characters are then written in destination.txt

(b) Write characters "XYZ" into file destination.txt

(c) Repeat the previous steps until the end of file source.txt. The last read step may not have 100 characters.