Your shell should then be modified to support the $\text{'}>\text{'}$ and $\text{'}<\text{'}$ redirection operators, where $\text{'}>\text{'}$ redirects the output of a command to a file and $\text{'}<\text{'}$ redirects the input to a command from a file. For example, if a user enters

osh$>$ls $>$ out.txt

the output from the ls command will be redirected to the file out.txt$.$ Similarly, input can be redirected as well. For example, if the user enters

osh$>$sort $<$ in$.$txt

the file in$.$txt will serve as input to the sort command.

Managing the redirection of both input and output will involve using the dup$2()$ function, which duplicates an existing file descriptor to another file descriptor. For example, if fd is a file descriptor to the file out.txt$,$ the call

dup$2($fd$,$ STDOUT$\_$FILENO$)$;

duplicates fd to standard output $($the terminal$).$ This means that any writes to standard output will in fact be sent to the out.txt file.

You can assume that commands will contain either one input or one output redirection and will not contain both. In other words, you do not have to be concerned with command sequences such as sort $<$ in$.$txt $>$ out.txt$.$