shell.c below is a stripped down shell program. It will run a Unix command without any arguments. Copy

and save the program as shell.c. Modify the program so that it can execute any shell command. It should

be able to take at least 2 arguments. Usually, you need to parse the command line you enter. Using execvp

instead of execlp will probably help. It should work on any UNIX command consisting of 0-2 arguments

after the command entered by the user, and be error free. The following are a few test cases that the user

could enter.

$ cp file1 file2

$ ls -l

$ who

char *strtok(char *str, const char *delim)

is a useful function for parsing the input string. You

can see below how it used " " as a delimiter to get everything before that character. You can specify " " as

a delimiter to split the string into arguments. The first time you use it, give it a string as the first parameter

to tokenize. This will return the first token. You can then use it subsequent times with NULL as the first

parameter and it will return subsequent tokens in order. After the last token was returned, it returns NULL.

For example if you wrote:

char

input [ ] = " Hello World ! " ;

strtok ( input , " " ) ;

strtok (NULL, " " ) ;

strtok (NULL, " " ) ;

...the first call would return "Hello". The second call would return "World!". And the third call would

return NULL.