POPEN(3S)           UNIX Programmer's Manual            POPEN(3S)

NAME
     popen, pclose - initiate pipe I/O to/from a process

SYNOPSIS
     #include <stdio.h>

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

     int pclose (stream)
     FILE *stream;

HP-UX COMPATIBILITY
     Level:    HP-UX/RUN ONLY

     Origin:   System V

DESCRIPTION
     The arguments  to  _p_o_p_e_n  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.   _P_o_p_e_n
     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 _p_o_p_e_n should be closed by  _p_c_l_o_s_e,  which
     waits  for  the  associated process to terminate and returns
     the exit status of the command.

     Because open files are shared, a type r command may be  used
     as an input filter, and a type w as an output filter.

SEE ALSO
     pipe(2), wait(2), fclose(3S), fopen(3S), system(3S).

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

     _P_c_l_o_s_e returns  -1  if  _s_t_r_e_a_m  is  not  associated  with  a
     "_p_o_p_e_ned" command.

BUGS
     Only one stream opened by _p_o_p_e_n 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, e.g. with _f_f_l_u_s_h; see _f_c_l_o_s_e(3S).