#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <errno.h> #include <string.h> #include <unistd.h> #include <stdio.h> typedef struct { char* filename; /* this file is the pipe (set by user) */ char is_server; /* this is set by open_control_file */ int fd; /* this is set by open_control_file */ } single_instance_struct; /* returns fd, is_server is set to -1 if server, 0 if client */ int open_control_file(single_instance_struct* str) { struct stat buf; if(stat(str->filename,&buf)) { mkfifo(str->filename,128|256); str->is_server=-1; str->fd=open(str->filename,O_NONBLOCK|O_RDONLY); } else { str->fd=open(str->filename,O_NONBLOCK|O_WRONLY); if(errno==ENXIO) { str->is_server=-1; str->fd=open(str->filename,O_NONBLOCK|O_RDONLY); } else str->is_server=0; } return(str->fd); } void delete_control_file(single_instance_struct* str) { remove(str->filename); } void close_control_file(single_instance_struct* str) { close(str->fd); } typedef void (*event_dispatcher)(char* message); int get_next_message(char* buffer,int len,single_instance_struct* str,int usecs) { struct timeval tv; fd_set fdset; int num_fds; FD_ZERO(&fdset); FD_SET(str->fd,&fdset); tv.tv_sec=0; tv.tv_usec=usecs; num_fds=select(str->fd+1,&fdset,NULL,NULL,&tv); if(num_fds) { int reallen; reallen=read(str->fd,buffer,len); if(reallen==0) { close(str->fd); str->fd=open(str->filename,O_NONBLOCK|O_RDONLY); num_fds--; } buffer[reallen]=0; #ifdef DEBUG_1INSTANCE if(reallen!=0) fprintf(stderr,"message received: %s.\n",buffer); #endif } return(num_fds); } int dispatch_event(single_instance_struct* str,event_dispatcher dispatcher,int usecs) { char buffer[1024]; int num_fds; if((num_fds=get_next_message(buffer,1024,str,usecs)) && buffer[0]) dispatcher(buffer); return(num_fds); } int loop_if_server(single_instance_struct* str,event_dispatcher dispatcher) { open_control_file(str); if(str->is_server) { while(1) dispatch_event(str,dispatcher,50); } return(str->fd); } void send_message(single_instance_struct* str,char* message) { #ifdef DEBUG_1INSTANCE int i= #endif write(str->fd,message,strlen(message)); #ifdef DEBUG_1INSTANCE fprintf(stderr,"send: %s => %d(%d)\n",message,i,strlen(message)); #endif } #ifdef DEBUG_MAIN #include <stdio.h> #include <stdlib.h> single_instance_struct str1 = { "/tmp/1instance" }; void my_dispatcher(char* message) { #ifdef DEBUG_1INSTANCE fprintf(stderr,"Message arrived: %s.\n",message); #endif if(!strcmp(message,"quit")) { delete_control_file(str1); exit(0); } } int main(int argc,char** argv) { int i; loop_if_server(str1,my_dispatcher); for(i=1;i<argc;i++) send_event(str1,argv[i]); return(0); } #endif