Write a C program myls1 whose behavior resembles that of the system command ls. myls1 must accept the following parameters:

$ myls1 [-ars] [directory] 

If myls1 is provided with no parameters, it lists the names of all files in the current directory, one file name per line.

directory specifies the name of a directory, in which case myls1 lists the names of files within that directory.

-a switch forces myls1 to display the names of hidden files (whose names start with a "."). In the absence of this switch, hidden files are not listed.

-s switch sorts the filenames in the lexicographical order.

-r switch sorts the filenames in the reverse lexicographical order.

Use the following test cases when running myls1 from the directory at the same level with dirA and dirB:

$ myls1 $ myls1 -a $ myls1 -s dirA $ myls1 -a dirB $ myls1 -r dirA/dirA1 $ myls1 dirB/dirB1