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Full Discussion: How to write to stdin of another program (program A -> [stdin]program B)
Top Forums UNIX for Dummies Questions & Answers How to write to stdin of another program (program A -> [stdin]program B) Post 302220958 by redoubtable on Saturday 2nd of August 2008 12:32:50 PM
Old 08-02-2008
/*
* here's how you can do it...
* using popen()
*
#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define READ 0
#define WRITE 1

pid_t
popen2(const char *command, int *infp, int *outfp)
{
int p_stdin[2], p_stdout[2];
pid_t pid;

if (pipe(p_stdin) != 0 || pipe(p_stdout) != 0)
return -1;

pid = fork();
if (pid < 0)
return pid;
else if (pid == 0)
{
close(p_stdin[WRITE]);
dup2(p_stdin[READ], READ);
close(p_stdout[READ]);
dup2(p_stdout[WRITE], WRITE);
execl("/bin/sh", "sh", "-c", command, NULL);
perror("execl");
exit(1);
}

if (infp == NULL)
close(p_stdin[WRITE]);
else
*infp = p_stdin[WRITE];
if (outfp == NULL)
close(p_stdout[READ]);
else
*outfp = p_stdout[READ];
return pid;
}

/*
* now in main... infp will be the stdin (in file descriptor)
* and outfp will be the stdout (out file descriptor)
* have fun
*/

int
main(int argc, char **argv)
{
int infp, outfp;
char buf[128];

if (popen2("your-program-B", &infp, &outfp) <= 0)
{
printf("Unable to exec your-program-B\n");
exit(1);
}

memset (buf, 0x0, sizeof(buf));

write(infp, "Z\n", 2);
write(infp, "D\n", 2);
write(infp, "A\n", 2);
write(infp, "C\n", 2);
close(infp);
read(outfp, buf, 128);
printf("buf = '%s'\n", buf);
return 0;
}
 

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LEARN ABOUT OPENSOLARIS

newterm

initscr(3XCURSES)					  X/Open Curses Library Functions					 initscr(3XCURSES)

NAME

       initscr, newterm - screen initialization functions

SYNOPSIS

       cc [ flag... ] file... -I /usr/xpg4/include  -L	/usr/xpg4/lib 
	-R  /usr/xpg4/lib  -lcurses  [ library... ]

       c89 [ flag... ] file... -lcurses [ library... ]

       #include <curses.h>

       WINDOW *initscr(void);

       SCREEN *newterm(char *type, FILE *outfp, FILE *infp);

PARAMETERS

       type	Is a string defining the terminal type to be used in place of TERM.

       outfp	Is a pointer to a file to be used for output to the terminal.

       infp	Is the pointer to a file to be used for input to the terminal.

DESCRIPTION

       The  initscr()  function  initializes  X/Open  Curses  data  structures,  determines  the  terminal  type,  and	ensures  the first call to
       refresh(3XCURSES) clears the screen.

       The newterm() function opens a new terminal with each call.  It should be used instead of initscr() when the program  interacts	with  more
       than one terminal.  It returns a variable of type SCREEN, which should be used for later  reference to that terminal. Before program termi-
       nation, endwin() should be called for each terminal.

       The only functions that you can call before calling initscr() or  newterm() are filter(3XCURSES), ripoffline(3XCURSES), slk_init(3XCURSES),
       and use_env(3XCURSES).

RETURN VALUES

       On success, the initscr() function returns a pointer to stdscr; otherwise, initscr() does not return.

       On success, the newterm() function returns a pointer to the specified  terminal; otherwise, a null pointer is returned.

ERRORS

       None.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Unsafe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       del_curterm(3XCURSES),	  delscreen(3XCURSES),	   doupdate(3XCURSES),	   endwin(3XCURSES),	 filter(3XCURSES),    libcurses(3XCURSES),
       slk_attroff(3XCURSES), use_env(3XCURSES), attributes(5), standards(5)

SunOS 5.11							    5 Jun 2002							 initscr(3XCURSES)
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