named fifo C issue -

i have c code:

#define bufsize 256  int main ( int argc, char *argv[]) {     int fdin;     int fdout;      if( argc != 3)     {         perror("argument error");         exit(1);     }      if( (fdin = open(argv[1], o_rdonly ) )<0)     {         perror("pipe input error open");         exit(1);     }      if( (fdout = open(argv[2], o_wronly ) )<0)     {         perror("pipe input error open");         exit(1);     }       int c = 2;     while(c--)     {         char var1[bufsize];         char var2[bufsize];         char string[100];          memset(var1, 0, sizeof(var1));         memset(var2, 0, sizeof(var2));         memset(string, 0, sizeof(string));          if( readline(fdin, var1, sizeof(var1)) == 0)         {             printf("exit1\n");             exit(0);         }          if( readline(fdin, var2, sizeof(var2)) == 0)         {             printf("exit2\n");             exit(0);         }          removenewline(var1);         removenewline(var2);          printf("%s\n",var1);         printf("%s\n",var2);          int n = atoi(var1);         int m = atoi(var2);          if (n!=0 && m % n == 0 ) {              sprintf(string,"multiple\n");          }         else{             sprintf(string,"negative\n");          }          printf("%s", string);         writeline(fdout, string, strlen(string));     }     close(fdout);     close(fdin);     exit(0); } 

this program accepts 2 inputs: first input fifo's name , second output fifo's name. program this: reads in input fifo 2 numbers , establishes if second number multiple of first number , writes on output fifo "multiple" or "negative". 2 times; problem when executed second loop first readline returns 0 , prints exit1. program should not stop on readline pending content in fifo?

functions used in program:

int readline( int fd, char* str, int buffersize) {     return readtodel(fd, '\n', str, buffersize); }  int readtodel( int fd, char delimiter, char* str, int buffersize) {     int n;     int byteletti =0;     int index=0;        /* read characters until null or end-of-input */     {          if( (n = read (fd, str+index, 1)) < 0)         {             perror("errore: lettura dal file descriptor fallita");             exit(1);         }         byteletti+=n;      }     while (n > 0 && *(str+index++) != delimiter && index < buffersize);          return byteletti; /* return false if end-of-input */ } 

for testing program this: open first terminal , write in input fifo in way:

echo "4" > input  echo "8" > input 

then open other terminal , execute program in way:

./program input output 

and when program blocked on writeline(fdout, string, strlen(string)); ( because there isn't reader on output fifo) open other terminal , : cat output

and get(based on input):

multiple exit1 

and dont understand why. should not wait until more input on input fifo?