What will be printed in the console?
The child process reads one character from the FIFO, which is 'x', stores it in the variabile c and prints it. Therefore, the output will be x and a newline because of ‘\n’.
What will be printed in the console if line 18 is moved between lines 9-10?
Moving unlink("fifo") to between lines 9-10 would unlink the FIFO immediately after the child process reads and prints 'x'. Since the unlinking happens after the child process has finished its read operation, it doesn't change the output. The output remains x.
How is the program execution affected if line 4 is moved between lines 5-6?
If mkfifo("fifo", 0600) is moved to between lines 5-6, the FIFO file creation will be performed by the child process after the fork. The parent process will then fail to open the FIFO file in write mode (O_WRONLY) because the FIFO file won't exist yet when the parent tries to open it. This would likely result in an error, and the program won't print anything.
Returns -1 and moves on
In what situation will the program display 'a'?
The program would display 'a' if the write call in the parent process fails to write any data into the FIFO, or if there is any error in reading from the FIFO that results in the child process using the default value of c, which is initialized to 'a'.
Explain the role of the arguments of function mkfifo on line 4.
The function mkfifo("fifo", 0600) creates a FIFO special file named "fifo". The argument "fifo" specifies the name of the FIFO file, and 0600 sets the file permissions, allowing read and write access only to the file owner.
What will be the content of file x/a.txt seen in the column on the right after running the script with argument abc?
abc
def
What will be the content of file x/b.txt seen in the column on the right after running the script with argument abc?
abc
abc
abc
What will be the content of file x/c.txt seen in the column on the right after running the script with arguments abc def?
def_def
def
def_def_def
def
Explain in detail the condition on line 7.
The condition elif [grep -E "^$A(_+$A)*$" $F | wc -l -gt 1 ]; checks if there are more than one (-gt 1) lines (wc -l) in the file $F that match the pattern ^$A(_+$A)*$. This pattern matches lines starting with $A followed by zero or more pairs of one or more underscores followed by an $A.
Explain in detail the regular expression on line 8.
The regular expression ^$A(_{1,}$A){0,}$ on line 8 matches lines starting with $A, followed by zero or more pairs of one or more underscores followed by an $A.
