HPUX system[3s]

 system(3S)                                                       system(3S)





 NAME
      system() - issue a shell command

 SYNOPSIS
      #include <stdlib.h>

      int system(const char *command);

 DESCRIPTION
      system() executes the command specified by the string pointed to by
      command.  The environment of the executed command is as if a child
      process were created using fork() (see fork(2)), and the child process
      invoked the sh-posix(1) utility via a call to execl() (see execl(2))
      as follows:

           execl("/bin/posix/sh", "sh", "-c", command, 0);

      system() ignores the SIGINT and SIGQUIT signals, and blocks the
      SIGCHLD signal, while waiting for the command to terminate.  If this
      might cause the application to miss a signal that would have killed
      it, the application should examine the return value from system() and
      take whatever action is appropriate to the application if the command
      terminated due to receipt of a signal.

      system() does not affect the termination status of any child of the
      calling processes other than the process or processes it itself
      creates.

      system() does not return until the child process has terminated.

    Application Usage
      If the return value of system() is not -1, its value can be decoded
      through the use of the macros described in <sys/wait.h>.  For
      convenience, these macros are also provided in <stdlib.h>.

      Note that, while system() must ignore SIGINT and SIGQUIT and block
      SIGCHLD while waiting for the child to terminate, the handling of
      signals in the executed command is as specified by fork(2) and
      exec(2).  For example, if SIGINT is being caught or is set to SIG_DFL
      when system() is called, the child is started with SIGINT handling set
      to SIG_DFL.

      Ignoring SIGINT and SIGQUIT in the parent process prevents
      coordination problems (such as two processes reading from the same
      terminal) when the executed command ignores or catches one of the
      signals.

 RETURN VALUE
      If command is null, system() returns non-zero.





 Hewlett-Packard Company            - 1 -     HP-UX Release 9.0: August 1992






 system(3S)                                                       system(3S)





      If command is not null, system() returns the termination status of the
      command language interpreter in the format specified by waitpid(2).
      The termination status of the command language interpreter is as
      specified for sh-posix(1), except that if some error prevents the
      command language interpreter from executing after the child process is
      created, the return value from system() is as if the command language
      interpreter had terminated using _exit(127).  If a child process
      cannot be created, or if the termination status for the command
      language interpreter cannot be obtained, system() returns -1 and sets
      errno to indicate the error.

 DIAGNOSTICS
      system() forks to create a child process which, in turn, exec()s
      /bin/posix/sh in order to execute string.  If the fork fails, system()
      returns -1 and sets errno.  If the exec fails, system() returns the
      status value returned by waitpid() (see waitpid(2)) for a process that
      terminates with a call of exit(127).

 ERRORS
      If errors are encountered, system() sets errno values as described by
      fork(2).

 FILES
      /bin/posix/sh

 SEE ALSO
      sh(1), fork(2), exec(2), waitpid(2).

 STANDARDS CONFORMANCE
      system(): AES, SVID2, XPG2, XPG3, XPG4, POSIX.2, ANSI C
























 Hewlett-Packard Company            - 2 -     HP-UX Release 9.0: August 1992