2018-11-14 Handling Arguments like a boss

posted Nov 14, 2018, 10:49 AM by Konstantinovich Samuel   [ updated Nov 14, 2018, 12:08 PM ]


With your table buddy, do the following in the repo "MKS65C-parseargs"


strsep is a function in string.h used to help parse strings
  • strsep( <SOURCE>, <DELIMITER> )
  • Locates the first occurrence of any character in the DELIMITER string and replaces it with NULL
  • Returns the beginning of the original string
  • sets the source string pointer  to point to the index 1 byte after the location of the new NULL
  • Since the source variable's value is changed, it must be a pointer to a string.
  • To test it out, try the following code:
  • char line[100] = "woah-this-is-cool";
    char *s1 = line;
    printf("[%s]\n", strsep( &s1, "-" ));
    printf("[%s]\n", s1);

Write a function that uses strsep to parse a line of arguments
  • Use the following header: char ** parse_args( char * line );
  • It should take a string with the command line invocation of a program (like "ls -a -l")
    • Note that there is a " " between each argument
  • Return an array of pointers to each individual argument in the parameter string, that could be used for execvp()
  • For example, the following code should work (assuming all variables are declared appropriately:
    • char ** args = parse_args( line );
      execvp(args[0], args);
  • You can make the following assumptions:
    • There is only 1 space between each argument in the original string
    • The original string contains no more than 5 arguments
    • The original string is correctly formatted

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