Function: system
Section: programming/specific
C-Name: gpsystem
Prototype: ls
Help: system(str): str being a string, execute the system command str.
Doc: \var{str} is a string representing a system command. This command is
 executed, its output written to the standard output (this won't get into your
 logfile), and control returns to the PARI system. This simply calls the C
 \kbd{system} command. Return the shell return value (which is system-dependent).
 Beware that UNIX shell convention for boolean is opposite to GP, true is $0$
 and false is non-$0$.
 \bprog
 ? system("test -d /") \\ test if '/' is a directory (true)
 %1 = 0
 ? system("test -f /") \\ test if '/' is a file (false)
 %2 = 1
 @eprog
