Program Execution

• This is chapter 27, you should read it.
• execve
  • unistd.h
  • int execve(const char *filename, char *const argv[], char *const envp[]);
    • filename is the executable file you wish to run.
      • This should be an binary file.
      • Or a script starting with a structured comment
        • #! interpreter
      • It can be an absolute or relative path
      • But not a ~ path, why?
    • argv is an array of strings representing the command line arguments.
    • envp is an array of strings representing the environment variable.
    • Both should be null terminated.
    • It should not return.
  • Starting on page 612 is a list of what happens to attributes when fork and exec are called.
    • This is 4 pages long.
    • It also contains system commands to change these things.
• There is a set of library functions that make exec easier
  • Man 3p exec
  • int execl(const char *path, const char *arg0, ... /*, (char *)0 */);
  • int execle(const char *path, const char *arg0, ... /*, (char *)0, char *const envp[]*/);
  • int execlp(const char *file, const char *arg0, ... /*, (char *)0 */);
  • int execv(const char *path, char *const argv[]);
  • int execve(const char *path, char *const argv[], char *const envp[]);
  • int execvp(const char *file, char *const argv[]);
  • int fexecve(int fd, char *const argv[], char *const envp[]);
  • The path name is given for most
    • lp and vp do not, they search for a file name in the PATH environment variable.
  • *l take a long argument list.
  • *v expect a vector for the argument list.
  • *e specify the environment list, otherwise use the parent processes.