p2open(3GEN)					     String Pattern-Matching Library Functions					      p2open(3GEN)

NAME

       p2open, p2close - open, close pipes to and from a command

SYNOPSIS

       cc [ flag ... ] file ... -lgen [ library ... ]
       #include <libgen.h>

       int p2open(const char *cmd, FILE *fp[2]);

       int p2close(FILE *fp[2]);

DESCRIPTION

       p2open()  forks	and  execs a shell running the command line pointed to by cmd. On return, fp[0] points to a FILE pointer to write the com-
       mand's standard input and fp[1]	points to a FILE pointer to read from the command's  standard output.
	In this way the program has control over the input and output of the command.

       The function returns 0 if successful; otherwise, it returns -1.

       p2close() is used to close the file pointers that p2open() opened.  It waits for the process to terminate and returns the  process  status.
       It returns 0 if successful; otherwise, it returns -1.

RETURN VALUES

       A common problem is having too few file descriptors. p2close() returns -1 if the two file pointers are not from the same p2open().

EXAMPLES

       Example 1: Example of file descriptors.

       #include <stdio.h>
       #include <libgen.h>

       main(argc,argv)
       int argc;
       char **argv;
       {
	    FILE *fp[2];
	    pid_t pid;
	    char buf[16];

	       pid=p2open("/usr/bin/cat", fp);
	       if ( pid == -1 ) {
		 fprintf(stderr, "p2open failed
");
		 exit(1);
	    }
	    write(fileno(fp[0]),"This is a test
", 16);
	    if(read(fileno(fp[1]), buf, 16) <=0)
		 fprintf(stderr, "p2open failed
");
	    else
		 write(1, buf, 16);
	    (void)p2close(fp);
       }

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Unsafe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       fclose(3C), popen(3C), setbuf(3C), attributes(5)

NOTES

       Buffered  writes  on fp[0] can make it appear that the command is not listening. Judiciously placed fflush() calls or unbuffering fp[0] can
       be a big help; see fclose(3C).

       Many commands use buffered output when connected to a pipe. That, too, can make it appear as if things are not working.

       Usage is not the same as for popen(), although it is closely related.

SunOS 5.10							    29 Dec 1996 						      p2open(3GEN)