ref: 347bb2a7a7110e55debd5ebe57ba03bbe315c5ba
dir: /sys/src/cmd/lp/ipcopen.c/
#include <u.h> #include <libc.h> int ppid; /* * predefined */ void pass(int from, int to); /* * Connect to given datakit port */ main(int argc, char *argv[]) { int fd0, fd1; int cpid; char c; char *cp, *devdir, *buf; if (argc != 4) { fprint(2, "usage: %s destination network service\n", argv[0]); exits("incorrect number of arguments"); } if(!(cp = malloc((long)(strlen(argv[1])+strlen(argv[2])+strlen(argv[3])+8)))) { perror("malloc"); exits("malloc failed"); } sprint(cp, "%s!%s!%s", argv[2], argv[1], argv[3]); if (dial(cp, &devdir, 0) < 0) { fprint(2, "dialing %s\n", cp); perror("dial"); exits("can't dial"); } /* * Initialize the input fd, and copy bytes. */ if(!(buf = malloc((long)(strlen(devdir)+6)))) { perror("malloc"); exits("malloc failed"); } sprint(buf, "%s/data", devdir); fd0=open(buf, OREAD); fd1=open(buf, OWRITE); if(fd0<0 || fd1<0) { print("can't open", buf); exits("can't open port"); } ppid = getpid(); switch(cpid = fork()){ case -1: perror("fork failed"); exits("fork failed"); case 0: close(0); close(fd1); pass(fd0, 1); /* from remote */ hangup(fd0); close(1); close(fd0); exits(""); default: close(1); close(fd0); pass(0, fd1); /* to remote */ hangup(fd1); close(0); close(fd1); exits(""); } } void pass(int from, int to) { char buf[1024]; int ppid, cpid; int n, tot = 0; while ((n=read(from, buf, sizeof(buf))) > 0) { if (n==1 && tot==0 && *buf=='\0') break; tot += n; if (write(to, buf, n)!=n) { perror("pass write error"); exits("pass write error"); } } }