Design and implement a simple shell program to read a command with a file redirection. here we use the following file-redirection symbols as follow: "in=infile" for input file named "infile", "out=outfile" for output file named "outfile", "app=appfile" for output to be appended a file named "appfile". for example, "ls out=out. txt" will output the result of the command to a file named out. txt.