2 system - issue a shell command
13 This function excutes the shell command found in the srtring, cmd.
14 The return value is system dependent. On POSIX P1003.1 compliant
15 systems the return value is defined by the waitpid system call.
16 Typically a shell command that returns with a 0 exit status will
17 cause this function to return a 0 value. On some systems, a shell
18 command that returns with an exit status of e will cause this
19 function to return e*256. Core dumps, termination due to signals
20 and other waitpid values will change the return value.
22 On POSIX P1003.1 compliant systems, if cmd is empty then this function
23 will determine if the shell is executable. If the shell is executable,
24 0 is returned otherwise non-zero is returned.
35 Sun Jul 9 03:21:48 PDT 1995