More on exec

• execvp and execlp search for the executable in the environment variable PATH
• The standard library functions getenv, setenv, unsetenv and putenv
  • #include <stdlib.h>
  • char *getenv(const char *name);
  • int setenv(const char *name, const char *value, int overwrite);
    • overwrite = 0, value not changed if the value was not set.
    • overwrite != 0, value changed if the value was not set
  • int putenv(char *string);
  • int unsetenv(const char *name);
  • Values are stored as strings: "var=value"
• Running scripts:
  • As we have discussed if the file begins with #! /path/to/interpreter interpreter_args
  • There can be only one argument in the first line
  • In bash
    • $0 is the program name (argv[0]);
    • $# is the number of arguments.
    • $* is an arry of arguments, not including argv[0]
  • Take a quick look at foo.sh
• The system function
  • stdlib.h
  • int system(const char *command);
    • fork -> exec -> waitpid