system(3) [netbsd man page]

SYSTEM(3)						   BSD Library Functions Manual 						 SYSTEM(3)

NAME

     system -- pass a command to the shell

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <stdlib.h>

     int
     system(const char *string);

DESCRIPTION

     The system() function hands the argument string to the command interpreter sh(1).	The calling process waits for the shell to finish execut-
     ing the command, ignoring SIGINT and SIGQUIT, and blocking SIGCHLD.

     If string is a NULL pointer, system() will return non-zero, if the command interpreter is available, or zero if none is available.  Other-
     wise, system() returns the termination status of the shell in the format specified by waitpid(2).

RETURN VALUES

     If a child process cannot be created, or the termination status of the shell cannot be obtained, system() returns -1 and sets errno to indi-
     cate the error.  If execution of the shell fails, system() returns the termination status for a program that terminates with a call of
     exit(127).

SEE ALSO

     sh(1), execve(2), waitpid(2), popen(3), shquote(3)

STANDARDS

     The system() function conforms to ANSI X3.159-1989 (``ANSI C89'') and IEEE Std 1003.2-1992 (``POSIX.2'').

CAVEATS

     Never supply the system() function with a command containing any part of an unsanitized user-supplied string.  Shell meta-characters present
     will be honored by the sh(1) command interpreter.

BSD
								  August 2, 2007							       BSD

system(3)						     Library Functions Manual							 system(3)

NAME

       system -  Executes a shell command

LIBRARY

       Standard C Library (libc.so, libc.a)

SYNOPSIS

       #include <stdlib.h>

       int system(
	       const char *string);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       system():  XPG4, XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Specifies a valid sh shell command.

	      If string is NULL (0), the system() function tests the accessibility of the sh command interpreter.

	      If  string  is not NULL, the system() function passes the parameter to the sh command, which interprets string as a command and exe-
	      cutes it.

DESCRIPTION

       The system() function passes the string parameter to the sh command, which interprets string as a command and executes it.

       The system() function invokes the fork() function to create a child process that in turn uses the exec function to run sh, which interprets
       the shell command contained in the string parameter.  The current process waits until the shell has completed before returning.

RETURN VALUES

       If  the	string parameter is NULL, the system() function returns 0 if it is unable to access the command interpreter or a non-zero value if
       sh is accessible.

       If the string parameter is not NULL, upon successful completion by sh, the system() function returns the exit status of the  shell  process
       in the form that wait(2) returns.  Otherwise, the system() function returns a value of -1 and sets errno to indicate the error.

       Exit status 127 indicates that the shell could not be executed.

       Note that the exit status should only be interpreted using the macros described in wait(2) and defined in the sys/wait.h header file.

ERRORS

       The  system() function sets errno to the specified values for the following conditions: The status of the child process created by system()
       is no longer available.

       In addition, the system() function may set errno values as described by fork().

RELATED INFORMATION

       Functions: exec(2), exit(2), fork(2), wait(2)

       Commands: sh(1)

       Standards: standards(5) delim off

																	 system(3)