pipe() read(), write() - more then 128Kb of data
Hello all,
Thanking in advance for the answers again!
I have a program reads from a file then pipes it to a Unix filter program, this last program adds lines to the original file, then prints it on the screen.
I tested my program with a 116K file, it worked, but then I tried a larger file (400+ Kb) and it halted. The program froze, didn't do anything, as if it's blocking.I found out that a 127-128 KB file will still work, but a larger file will not.
What is causing this?? Is it because I somehow have to manage the reads and writes?
My program so far:
Code:
/* Chihwah Li
* elke textregel in een bestand voorzien van regelnummer.
*/
#include <stdio.h>
#include <sys/types.h> //
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <string.h>
#include <netinet/in.h>
#include <sys/time.h>
struct timeval start, finish ;
int msec;
int main(int argc, char** argv) {
int X[2], Y[2];
void Parent(int *X, int *Y, int fp);
void Child(int *X, int *Y, int noLines);
pipe(X);
pipe(Y); /* Create Communication Channels */
char *inFile; //
int fp, noLines; //
if (argc != 2 && argc != 3) {
fprintf(stderr, "usage: %s [-n] <filename>\n", argv[0]);
return (EXIT_FAILURE);
}
// dubbele check of de argumenten goed staan
inFile = (argc == 2) ? argv[1] : argv[2];
noLines = (argc == 3) ? 1 : 0;
if ((noLines == 1) && (strcmp(argv[1],"-n") < 0)) {
fprintf(stderr,"usage: %s [-n] <filename>\n",argv[0]);
return (EXIT_FAILURE);
}
if ((fp = open( inFile, O_RDONLY)) == -1) {
perror("");
return (EXIT_FAILURE);
}
gettimeofday (&start, NULL); // Tijdmeting starten
switch (fork()) {
case 0: Child(X, Y, noLines);
break;
case -1: perror("Can\'t create child");
exit(1);
default: Parent(X, Y, fp);
}
if (close(fp) == -1) {
perror("close filename: ");
return (EXIT_FAILURE);
}
exit(0);
}
void Parent(int *X, int *Y, int fp) {
char c;
close(X[0]);
close(Y[1]);
while (read(fp, &c, 1) > 0){
write(X[1], &c, 1); /* read data from stdin */
}
close(X[1]);
while (read(Y[0], &c, 1) > 0){
write(1, &c, 1); /* write data to stdout */
}
// checken y en x of dat juist is
gettimeofday (&finish, NULL);
msec = finish.tv_sec * 1000 + finish.tv_usec / 1000;
msec -= start.tv_sec * 1000 + start.tv_usec / 1000;
fprintf(stderr, "Time: %d milliseconds\nPress [Enter] to see the uniq, sorted list: ", msec);
close(Y[0]);
wait(0);
}
void Child(int *X, int *Y, int noLines) {
close(X[1]);
close(Y[0]);
close(0);
dup(X[0]);
close(X[0]);
close(1);
dup(Y[1]);
close(Y[1]);
if (noLines == 0){
execlp("nl", "nl", NULL); // add line numbers
} else {
execlp("sed", "sed","'N;s/\n/\t/'", NULL); // remove line numbers
}
perror("fault by exec: ");
exit(1);
}
