preline.c

linux下qmail的源码 本人加了一些注释

//实用工具程序之一，作用是在将消息转发给相关程序前预处理这些消息

#include "fd.h"
#include "sgetopt.h"
#include "readwrite.h"
#include "strerr.h"
#include "substdio.h"
#include "exit.h"
#include "fork.h"
#include "wait.h"
#include "env.h"
#include "sig.h"
#include "error.h"

#define FATAL "preline: fatal: "

void die_usage()
{
  strerr_die1x(100,"preline: usage: preline cmd [ arg ... ]");
}

int flagufline = 1; char *ufline;
int flagrpline = 1; char *rpline;
int flagdtline = 1; char *dtline;

char outbuf[SUBSTDIO_OUTSIZE];
char inbuf[SUBSTDIO_INSIZE];
substdio ssout = SUBSTDIO_FDBUF(write,1,outbuf,sizeof outbuf);
substdio ssin = SUBSTDIO_FDBUF(read,0,inbuf,sizeof inbuf);

void main(argc,argv)
int argc;
char **argv;
{
  int opt;
  int pi[2];
  int pid;
  int wstat;
 
  sig_pipeignore();
 
  if (!(ufline = env_get("UFLINE"))) die_usage();
  if (!(rpline = env_get("RPLINE"))) die_usage();
  if (!(dtline = env_get("DTLINE"))) die_usage();
 
  while ((opt = getopt(argc,argv,"frdFRD")) != opteof)
    switch(opt) {
      case 'f': flagufline = 0; break;
      case 'r': flagrpline = 0; break;
      case 'd': flagdtline = 0; break;
      case 'F': flagufline = 1; break;
      case 'R': flagrpline = 1; break;
      case 'D': flagdtline = 1; break;
      default: die_usage();
    }
  argc -= optind;
  argv += optind;
  if (!*argv) die_usage();
 
  if (pipe(pi) == -1)
    strerr_die2sys(111,FATAL,"unable to create pipe: ");

  pid = fork();
  if (pid == -1)
    strerr_die2sys(111,FATAL,"unable to fork: ");

  if (pid == 0) {
    close(pi[1]);
    if (fd_move(0,pi[0]) == -1)
      strerr_die2sys(111,FATAL,"unable to set up fds: ");
    sig_pipedefault();
    execvp(*argv,argv);
    strerr_die4sys(error_temp(errno) ? 111 : 100,FATAL,"unable to run ",*argv,": ");
  }
  close(pi[0]);
  if (fd_move(1,pi[1]) == -1)
    strerr_die2sys(111,FATAL,"unable to set up fds: ");
 
  if (flagufline) substdio_bputs(&ssout,ufline);
  if (flagrpline) substdio_bputs(&ssout,rpline);
  if (flagdtline) substdio_bputs(&ssout,dtline);
  if (substdio_copy(&ssout,&ssin) != 0)
    strerr_die2sys(111,FATAL,"unable to copy input: ");
  substdio_flush(&ssout);
  close(1);
 
  if (wait_pid(&wstat,pid) == -1)
    strerr_die2sys(111,FATAL,"wait failed: ");
  if (wait_crashed(wstat))
    strerr_die2x(111,FATAL,"child crashed");
  _exit(wait_exitcode(wstat));
}