unix-socket-writer.c

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/sendfile.h>
#include <sys/stat.h>
#include <stdio.h>
#include <unistd.h>
#include <libgen.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

const struct sockaddr_un sockaddr={
  AF_UNIX,
  "/tmp/unix_socket"
};

const char * basename_argv0;
const char filename[]="/etc/bash_completion";

int main(int argc, char * const argv[]) {
  int sockfd,fd;
  ssize_t writesize;
  struct stat statbuf;
  int status;
  basename_argv0=basename(argv[0]);
  sockfd=socket(AF_UNIX,SOCK_STREAM,0);
  if (sockfd==-1) {
    fprintf(stderr,"%s: cannot open socket: %s\n",basename_argv0,strerror(errno));
    return (2);
  }
  status=connect(sockfd,(const struct sockaddr *)&sockaddr,sizeof(sockaddr));
  if (status!=0) {
    fprintf(stderr,"%s: cannot connect to socket: %s\n",basename_argv0,strerror(errno));
    return (2);
  }
  fd=open(filename,0);
  if (fd==-1) {
    fprintf(stderr,"%s: %s: %s\n",basename_argv0,filename,strerror(errno));
    return (2);
  }
  status=fstat(fd,&statbuf);
  if (status!=0) {
    fprintf(stderr,"%s: %s: %s\n",basename_argv0,sockaddr.sun_path,strerror(errno));
    return (2);
  }
  writesize=sendfile(sockfd,fd,NULL,statbuf.st_size);
  if (writesize==-1) {
    fprintf(stderr,"%s: cannot write to socket: %s\n",basename_argv0,strerror(errno));
    return (2);
  }
  status=close(sockfd);
  if (status!=0) {
    fprintf(stderr,"%s: cannot close sockfd: %s\n",basename_argv0,strerror(errno));
    return (2);
  }
  return (0);
}