POPEN(S)                 XENIX System V                  POPEN(S)



     Name
          popen, pclose - Initiates I/O to or from a process.

     Syntax
          #include <stdio.h>

          FILE *popen (command, type)
          char *command, *type;

          int pclose (stream)
          FILE *stream;

     Description
          The arguments to popen are pointers to null-terminated
          strings containing, respectively, a shell command line and
          an I/O mode, either ``r'' for reading or ``w'' for writing.
          popen creates a pipe between the calling process and the
          command to be executed.  The value returned is a stream
          pointer that can be used (as appropriate) to write to the
          standard input of the command or read from its standard
          output.

          A stream opened by popen should be closed by pclose, which
          waits for the associated process to terminate and returns
          the exit status of the command.  Because open files are
          shared between processes, a type ``r'' command may be used
          as an input filter, and a type ``w'' as an output filter.

     See Also
          pipe(S), wait(S), fclose(S), fopen(S), system(S)

     Diagnostics
          popen returns a null pointer if files or processes cannot be
          created, or if the shell cannot be accessed.

          pclose returns -1 if stream is not associated with a popened
          command.

     Notes
          Only one stream opened by popen can be in use at once.
          Buffered reading before opening an input filter may leave
          the standard input of that filter mispositioned.  Similar
          problems with an output filter may be forestalled by careful
          buffer flushing; see fclose(S).











     Page 1                                           (printed 8/7/87)