Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

SunOS 5.10 - man page for p2close (sunos section 3gen)

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

p2open, p2close - open, close pipes to and from a command
cc [ flag ... ] file ... -lgen [ library ... ] #include <libgen.h> int p2open(const char *cmd, FILE *fp[2]); int p2close(FILE *fp[2]);
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.
A common problem is having too few file descriptors. p2close() returns -1 if the two file pointers are not from the same p2open().
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\n"); exit(1); } write(fileno(fp[0]),"This is a test\n", 16); if(read(fileno(fp[1]), buf, 16) <=0) fprintf(stderr, "p2open failed\n"); else write(1, buf, 16); (void)p2close(fp); }
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |MT-Level |Unsafe | +-----------------------------+-----------------------------+
fclose(3C), popen(3C), setbuf(3C), attributes(5)
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)