execve(pathargsenvexecutes new program like execv(but additionally accepts dictionaryenvthat defines the environment in which the program runs env must be dictionary mapping strings to strings execvp(pathargslike execv(pathargsbut duplicates the shell' actions in searching for an executable file in list of directories the directory list is obtained from environ['path'execvpe(pathargsenvlike execvp(but with an additional environment variable as in the execve(function _exit(nexits immediately to the system with status nwithout performing any cleanup actions this is typically only done in child processes created by fork(this is also different than calling sys exit()which performs graceful shutdown of the interpreter the exit code is application-dependentbut value of usually indicates successwhereas nonzero value indicates an error of some kind depending on the systema number of standard exit code values may be definedvalue description ex_ok ex_usage ex_dataerr ex_noinput ex_nouser ex_nohost ex_notfound ex_unavailable ex_software ex_oserr ex_osfile ex_cantcreat ex_ioerr ex_tempfail ex_protocol ex_noperm ex_config no errors incorrect command usage incorrect input data missing input user doesn' exist host doesn' exist not found service unavailable internal software error operating system error file system error can' create output / error temporary failure protocol error insufficient permissions configuration error fork(creates child process returns in the newly created child process and the child' process id in the original process the child process is clone of the original process and shares many resources such as open files (unixf lib fl ff